Signal Hill City Council
March 14, 2023

Street Tree Master Plan
Prepared for:

City of Signal Hill
2175 Cherry Ave
Signal Hill, CA 90755
562.989.7300

CITY OF SIGNAL HILL
Key City Staff:

Thomas Bekele, Public Works Director
Margarita Beltran, Public Works Superintendent
Patrick Kelley, Contracts Manager
Cecil Looney, Deputy Director of Public Works
Kanesha Pompey, Administrative Assistant
Elena Ramos, Administrative Assistant
Ethan Rucker, Management Assistant
Jesus Saldaña, Associate Engineer
Rick Uribe, Maintenance Supervisor

SIGNAL HILL

STREET TREE MASTER PLAN
Prepared by:

SWA Group
Landscape Architecture,
Planning and Urban Design Firm
811 W. 7th Street, 8th Floor
Los Angeles, CA 90017
213.236.9090
With:

Rincon Consultants, Inc.
180 N Ashwood Avenue
Ventura, CA 93003
805.644.4455
i
Signal Hill From Hilltop Park. Photo: City of Signal Hill ii SIGNAL HILL STREET TREE MASTER PLAN

1.3 Existing Conditions
Pollution in the area is some of the worst in the state, and the city faces some inequality in terms of shade. Past tree planting created a mismatch between species and location, causing conflicts between trees, power lines, and underground utlities. All of these factors should be considerations in the placement of new street trees. Signal Hill's position on the border of two major watersheds means that its street trees can play a crucial role in helping to capture and filter stormwater, and could even be used to phytoremediate oil contamination.

1.4 Current Street Tree Conditions
Signal Hill has a 74% stocking rate of its street tree sites, meaning that over 1,000 sites are available be planted. 15% of the city's street trees are Chinese Elms, which are therefore not included in the updated palette in order to create a well-balanced urban forest. Less than 1% of Signal Hill's street trees are native, so any new trees planted should include a number of native species. Staff suggestions for which trees to avoid and which flourish in the city should also be taken into account, and are included in this section.

Section 2: Design & Management Plan

2.1 Guiding Goals & Objectives

1. Fill the vacant tree sites.
a. Increase the city’s tree canopy by 1% in so doing.
b. Continue to replace trees in a timely manner as needed. c. Tree-planting initiatives can help Signal Hill achieve this goal.

2. Ensure the long-term health and prosperity of the city’s street tree canopy by planting the right tree in the right place. a. Improve shade equity in the city by focusing on planting in areas of greater need.

Section 1: Background

1.1 Introduction
Signal Hill's street tree canopy provides many benefits for the city, including shade and beauty. This Street Tree Master Plan updates the 2010 plan, and provides a path to grow the street tree canopy with economic, ecological, and environmental justice factors in mind. The Community Forest includes all vegetation within an urban community, and street trees are a vital part of that forest. The information contained in this document aims to help Signal Hill take a holistic approach to improving its street tree canopy, within the context of the Community Forest.

The document can be used to help set policy and budget goals, and provides a practical way for the city to choose a particular tree for a particular site ("the right tree in the right place") as well as an updated palette emphasizing water-wise, native, and Climate Ready species. It includes design guidelines for future development in addition to planting and maintenance guidelines.

1.2 Planning Context
Signal Hill is located in a populous part of Southern California dominated by industry, such as oil production and trade through the nearby Ports of Los Angeles and Long Beach. The area was originally settled by the Tongva people and then later become farmland, a result of its position between two major rivers, the Los Angeles and the San Gabriel, which brought vital water and nutrients for crops. While coastal sage scrub and wet meadow ecologies originally dominated the land, current urbanization makes trees even more valuable for their role in mitigating pollution and Urban Heat Islands, capturing and filtering stormwater, and providing animal habitat.

EXECUTIVE SUMMARY
EXECUTIVE SUMMARY iii

2. Plant to attract and support wildlife.

3. Select trees and plantings adapted to the environmental conditions of the site.

4. Satisfy any functional reasons for the planting.

5. Integrate low impact development best management practices for stormwater within public right-of-way plantings, where practical.

6. Diversify types and species where possible.

Supporting Maintenance & Safety

1. Plant to provide the intended performance and aesthetic with the lowest water usage.

2. Ensure planting designs conform to current local and state regulations.

3. Consider the non-optimum conditions of street tree plantings when designing tree spacing.

4. Design tree spacing based on mature plant sizes.

5. Place trees away from conflicting uses.

6. Locate trees to minimize conflict with overhead utilities.

7. Locate trees to minimize conflict with underground utilities.

8. Provide planting spaces that accommodate healthy tree growth.

2.3 Design for the Future
Goals such as phytoremediation using street trees and the completion of a Community Forest Master Plan should be considered in the future, as well as the integration of composting and mulching programs. Issues of climate justice should be addressed whenever possible.

2.4 Species Selection Criteria
This section provides a course of action for the city to take when maintaining and selecting street trees, including diagrams for the procedures already in place for maintaining existing trees, a method for b. Use species well-adapted to local environmental conditions and design objectives.
c. Provide native animal habitat and well-adapted trees by planting native species.
d. Achieve a diverse and resilient forest by following the 10-20- 30 rule of community forestry.

3. Establish a high standard of maintenance and a sustainable care regimen for the city’s street trees.

4. Promote public awareness of and involvement in community forestry care and benefits.
e. Promote the community forestry program’s progress &
achievements.
f. Encourage collaboration between city departments, local community organizations, and public schools.
g. Encourage monetary and other contributions to the
community forestry program.
h. Participate in programs that support and promote the benefits of the community forest.

2.2 Planting Design Guidelines
Any new construction or renovation projects should include new street tree sites with irrigation installed, and modular suspended pavement systems are recommended. Additional detailed design recommendations for new development are included in this section, as well as Universal Planting Design Guidelines:

Enhancing Character & Aesthetics

1. Respect and emphasize the city’s geographic setting.

2. Complement existing trees and other vegetation.

3. Use trees to create a variety of spatial experiences.

Increasing Forest Resiliency

1. Use native species where appropriate.
iv SIGNAL HILL STREET TREE MASTER PLAN

4.2 Street Tree Policy Recommendations
This section delineates recommended changes to past street tree policy, including the stipulation that street trees cannot be trimmed or removed to protect a view, updated tree spacing and larger tree well sizes. The plan also recommends ways to encourage the growth of the street tree canopy and to protect existing trees.

4.3 Tree Planting Program
One of the most important things Signal Hill can do to reestablish a strong street tree canopy is to initiate a tree planting program, starting with filling empty sites and continuing to replace trees as they are removed. Choosing the appropriate tree for the site using this guide should aid in that endeavor. The city can work together with various nonprofits, such as Tree People, and government organizations, like CAL FIRE, to help them achieve this goal. If the city plants 250 trees per year over five years, the street tree stocking level should reach 100%.

4.4 Tree Maintenance Program
This plan recommends that the city consider pruning by species instead of geographic zone, create a pest-monitoring protocol, and follow local regulations for pruning. Hiring an independent tree consultant can help with these tasks. Additionally, a "Street Tree Report Card" could be created to help track the health of Signal Hill's street tree canopy. Finally, creating a Community Forest Master Plan is the next logical step to ensure a robust urban forest for the city of Signal Hill.

4.5 Tree Ordinance Upate
Modifications to the Signal Hill's Street Tree Ordinance are listed here.

4.6 Updated 2023 Street Tree Policy
Signal Hill's updated 2023 Street Tree Policy is included here. selecting a new tree for a vacant site, and a comprehensive selection method (pp. 60-63). Factors such as tree size, branch strength, root invasiveness, and proximity to utilities should be taken into account.

Larger and native species should be given priority. The section also denotes specific locations where palm trees can be planted, as well as trees that are in the street tree database but are actually on private property.

2.5 Street Tree Palette Selection

2.6 Street Tree Palette
Many factors were considered when choosing trees for the palette, including lists from other cities, species from the Climate Ready Trees study, and nursery availability. A list of resources is provided here in addition to the palette list (pp. 67-69) and the palette itself (pp. 70-81).

3.0 Planting & Maintenance

3.1 Planting the Tree
Provides detailed instructions for street tree planting, including standard planting details for the city of Signal Hill (pp. 95-97).

3.2 Maintaining the Tree
Provides practical information on street tree maintenance, especially irrigation, as well as common problems and solutions.

4.0 Findings & Updates

4.1 Introductory findings
This section briefly analyzes past street tree policy.

EXECUTIVE SUMMARY v

5.0 Community Participation & Education

5.1 Community Outreach
The city of Signal Hill included a community outreach program as part of the Street Tree Master Plan update process. The purpose of the outreach program was to notify the public of the project and provide education on the issues involved, as well as to solicit input from community members. It included public notifications, pop-up events, a community open house and a workshop, as well as an online survey. The city hosted a website about the plan with information on events and an interactive map.

5.2 Survey Slides with Results
Includes the slides used for the online survey via mentimeter.com, with the results from the survey.

5.3 Analysis & Integration
Key Findings
• Survey respondents recognize the value of street trees in their community
• Residents would like to see more trees in their city
• Planting more native and climate-adapted trees is important • Water use and aesthetics are key criteria for tree selection • Respondents do not value views over trees
The city should prioritize planting drought-tolerant native trees when possible, especially Island Oak and Western Redbud. Given appropriate space, survey-takers preferred larger, spreading trees to provide greater shade and relieve pollution; smaller trees were preferred to avoid conflicts with utilities. Working together with HOAs was also suggested.

5.4 Creation of a Community Forest Master Plan
The entire community benefits from an extensive, healthy, well-designed forest, beyond the limits of the street tree population. If possible, it is recommended that Signal Hill create such a comprehensive plan, involving trees not only in streets but parks, businesses, and residences.

Citizens and businesses can become involved in selecting, planting and maintaining trees, by funding projects or providing land. Institutions such as schools, libraries, and hospitals can help promote involvement, as well as non-profit organizations. The city should also continue to publicize the new Street Tree Master Plan and any subsequent plans to promote community involvement.

Appendix
The appendix includes the complete outreach survey results in spreadsheet form, as well as information on modular suspended pavement systems and a street tree inventory checklist. vi SIGNAL HILL STREET TREE MASTER PLAN

1.3g Public Works & Power Infrastructure

1.3h Current Street Tree Species Map

1.4 Current Street Tree Conditions

1.4a Snapshot of Signal Hill Street Trees

1.4b Tree Taxonomy

1.4c Native Tree Species

1.4d Tree Size Classifications

1.4e West Coast Arborists (WCA)
Recommendations & Categorizations

1.4f Benefits of Signal Hill's Trees

1.4g City Staff Perspectives

2.0 Design & Management Plan

2.1 Guiding Goals and Objectives

2.2 Planting Design Guidelines

2.3 Design for the Future

2.4 Species Selection Criteria

2.4a Palm Corridors

2.5 Street Tree Palette Selection & Resources

2.6 Street Tree Palette

2.7 Management Guidelines

3.0 Planting & Maintenance

3.1 Planting the Tree

3.1a Guidelines for Tree Planting

CONTENTS
List of Figures
List of Tables

1.0 Background

1.1 Introduction

1.1a Trees in Signal Hill

1.1b The Community Forest

1.1c Benefits of Trees

1.1d How to Use This Document

1.2 Planning Context

1.2a A Brief History of Signal Hill

1.2b Pre-Columbian Ecology

1.2c Natural Vegetation of Signal Hill

1.2d Native Ecologies: Coastal Sage Scrub

1.2e Native Ecologies: Wet Meadow

1.2f Native Ecologies: Trees & Animals

1.3g Signal Hill’s Position in the Region

1.3h Environmental Health

1.3 Existing Conditions

1.3a City of Signal Hill

1.3b Topography & Groundwater

1.3c Oil Infrastructure

1.3d Urban Heat Index & Current Tree Canopy

1.3e Tree Canopy Percentage by Census Tract

1.3f Tree Equity Score
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85 CONTENTS vii

4.4b Track Progress

4.4c Community Forest Master Plan

4.5 Tree Ordinance Update

4.6 Updated 2023 Street Tree Policy

5.0 Community Participation and Education

5.1 Community Outreach

5.1a Community Outreach Objectives

5.1b Community Outreach Methods

5.2 Survey Slides with Results

5.3 Analysis & Integration

5.4 Creation of a Community Forest Master Plan

5.4a Who to Involve in the Community

5.4b How to Involve the Community
Appendix
Outreach Survey Responses
Modular Suspended Pavement Systems
Inventory Checklist

3.1b Checklist for Planting

3.1c Preparing the Planting Area

3.1d Preparing Planting Holes and Placing the Tree

3.1e Staking the Tree

3.1f After The Tree Is in Place

3.1g Why Trees Sometimes Die After Planting

3.1h Signal Hill Standard Tree Planting Details

3.2 Maintaining the Tree

3.2a Pruning

3.2b Tree Removals

3.2c Tree Watering

3.2d Protection of Existing Trees

4.0 Findings & Updates

4.1 Introductory Findings

4.1a Street Tree Policy Analysis

4.1b 2010 Street Tree Master Plan Update Analysis

4.2 Street Tree Policy Recommendations

4.3 Tree Planting Program

4.3a Tree Planting Goals

4.3b Methods

4.3c Funding

4.3d Phasing Plan

4.4 Tree Maintenance Program

4.4a Maintenance Goals
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viii SIGNAL HILL STREET TREE MASTER PLAN

LIST OF FIGURES

1.0 Background
Figure 1.1.1: The Community Forest
Figure 1.2.1: Historic Ecology of Signal Hill
Figure 1.2.2: Signal Hill's Position in the Region, 1:480,000 Figure 1.2.3: Signal Hill's Position in the Region, 1:192,000 Figure 1.2.4: CalEnviroScreen Overall Score
Figure 1.2.5: CalEnviroScreen Pollution Burden
Figure 1.3.1: The City of Signal Hill, 1:28,800
Figure 1.3.2: Signal Hill Average Temperature & Precipitation Figure 1.3.3: Signal Hill Wind Direction
Figure 1.3.4: Topography and Groundwater
Figure 1.3.5: Oil Infrastructure
Figure 1.3.6: Watersheds of the Signal Hill Area
Figure 1.3.7: Urban Heat Index & Current Tree Canopy
Figure 1.3.8: Tree Canopy Percentage by Census Tract
Figure 1.3.9: Tree Equity Score
Figure 1.3.10: Public Works & Power Infrastructure
Figure 1.3.11: Current Street Tree Species Map
Figure 1.3.12: Current Street Tree Species Map, Zone 1
Figure 1.3.13: Current Street Tree Species Map, Zone 2
Figure 1.3.14: Current Street Tree Species Map, Zone 3
Figure 1.3.15: Current Street Tree Species Map, Zone 4
Figure 1.4.1: Native Tree Population
Figure 1.4.2: Trunk Diameter Distribution Chart
Figure 1.4.3: Diameter at Standard Height
Figure 1.4.4: Tree Height Distribution Chart
Figure 1.4.5: Tree Condition Chart
Figure 1.4.6: Site Type Chart
Figure 1.4.7: Site Status Chart

2.0 Design & Management Plan
Figure 2.1.1: The Right Tree in the Right Place
Figure 2.1.2: Survival Rates for Climate Ready Trees
Figure 2.1.3: Benefits of Native Plants
Figure 2.1.4: The 10-20-30 Rule of Urban Forestry
Figure 2.1.5: The Benefits of Trees
Figure 2.2.1: Tree Forms
Figure 2.2.2: Tree Planting Regulations
Figure 2.2.3: Existing vs. Suggested Street Tree
Planting Design
Figure 2.3.1: Possible Existing Phytoremediation in
Signal Hill Street Trees
Figure 2.4.1: Maintenance Protocol for Existing Trees
Figure 2.4.2: Method of Selecting New Trees for Vacant Sites Figure 2.4.3: Comprehensive Method of Selecting
New Trees for Vacant Sites
Figure 2.4.4: Selection Tree
Figure 2.4.5: Palm Corridors
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LIST OF FIGURES ix

3.0 Planting & Maintenance
Figure 3.1.1: Tree Size to Soil Volume Ratio, James Urban Figure 3.1.2: Underground Utilities
Figure 3.1.3: USDA Soil Types
Figure 3.1.6: Trees from Nurseries
Figure 3.1.7: Signal Hill Public Works Tree Well Planting Detail, Plan (212)
Figure 3.1.8: Signal Hill Public Works Parkway Street Tree Planting Detail (212)
Figure 3.1.9: Signal Hill Public Works Parkway Street Tree Planting Detail, Notes (212)
Figure 3.1.10: Signal Hill Public Works Parkway Street Tree Planting Detail Plan (212A)
Figure 3.1.11: Signal Hill Public Works Parkway Street Tree Planting Detail, Section (212A)
Figure 3.1.12: Signal Hill Public Works Parkway Street Tree Planting Detail, Plan (212A)

4.0 Findings & Updates
Figure 4.3.1: Phasing Plan
Figure 4.4.1: Street Tree Report Card
87 87
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114
30 30
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LIST OF TABLES
Table 1 Street Tree Numbers & Value
Table 2 Species Diversity
Table 3 Vacant Sites
Table 4 Top 5 Tree Families
Table 5 Top 5 Tree Genera
Table 6 Top 5 Tree Species
Table 7 Percent of Tree Removed by Genera
Table 8 Top Species Removed
Table 9 Benefits of Street Trees
Table 10 Street Tree Annual Benefits (iTree)
Table 11 Street Tree Annual Benefits (GIS)
Table 12 Canopy Statistics via iTree
Table 13 Canopy Statistics via GIS Data
Table 14 Signal Hill Current Street Tree Budget
Table 15 Species Performing Well
Table 16 Species to Consider for New Planting Palette
Table 17 Most Problematic Species
Table 18 Number of Trees Needed to Increase Total
Tree Canopy by 1%
Table 19 Infiltration Rates
Table 20 Soil Moisture
Table 21 Budget to Plant 1000 Trees in 5 years

1.0 BACKGROUND
SECTION 1: BACKGROUND 1

1.1 Introduction

1.1a Trees in Signal Hill
What defines the city of Signal Hill? Whether
it's the hill that gives it its name, the citizens
who make their home there, or the community
parks where those citizens gather together,
trees play a role in improving their wellbeing.

Trees prevent erosion and provide habitat for
animals living on the hill. They beautify homes
of residents, and can even lift their mood. They
provide shade for people recreating in parks,
and children enjoy climbing and playing around
them.

The city takes pride in its street trees, of which
there are over 3,000. But climate change,
economic factors, and other influences have
taken a toll on the street tree canopy of Signal
Hill: there are actually more than 1,000 vacant
street tree wells waiting to be replanted. As a
result, this plan will update the 2010 Street Tree
Master Plan, amend the existing Street Tree
Policy and Tree Planting Standard Ordinances,
and provide a map for the city to improve the
size and health of the city’s street canopy in
the coming years.

Street trees in Signal Hill. Photo: City of Signal Hill 2 SIGNAL HILL STREET TREE MASTER PLAN
Figure 1.1.1: The Community Forest
street trees
include: slowing of climate change, water
quality protection, better air quality, lower
air temperature, wildlife habitat, increased
property value, and improved quality of life.

Capitalizing on the benefits of a healthy tree
canopy will allow for a greener, more resilient
city. The holistic perspective of community
forestry—treating the community forest
as an integrated piece of infrastructure
that transcends property lines and political
jurisdictions—makes the Signal Hill Street
Tree Master Plan an essential framework for
sustainable development in the City of Signal
Hill.

Municipalities, local non-profit organizations,
community groups, residents, and businesses
are working together to promote, protect,
and replenish our urban forests with tangible
results. The basic means of overcoming the
stress that besets city trees and restoring the
vigor of the community forest is to correctly
plant the right tree in the right place and
provide it with proper care. Coupled with
community education and participation, these
are the essential recommendations of the
Signal Hill Street Tree Master Plan.

The potential benefits of urban street trees

1.1b The Community Forest
The term “community forest” generally
describes all vegetation – trees, shrubs,
grasses, and flowers, growing within an urban
or suburban environment, on both public and
private property. While this Plan focuses on
the City-maintained portion of the community
forest, a healthy community forest in its
entirety provides the maximum benefits to the
local community and ecology.

Urban trees are impacted by various stress
factors. The built environment covers and
compacts soil, vehicles collide with branches,
and polluted air damages foliage with
particulates, toxins, and acid rain. The acute
impacts of climate change—extreme heat,
drought, intensified wildfire—further challenge
the longevity of urban nature. Under these
stressors, street trees have an average life
expectancy of 19 to 28 years, while a tree
might live four or five times longer under ideal
conditions. As most species of trees take forty
years to mature, city street trees are often
adolescent and rarely reach a size where their
full benefits can be enjoyed.

Although hundreds of urban street trees are
removed annually due to death, declining
structure, or storm damage, public-private
partnerships can counteract these effects.

SECTION 1: BACKGROUND 3

1.1c Benefits of Trees
Physical & Environmental Economic Human
Trees have a positive impact on people’s physical &
mental health.

Studies have shown that patients with views of
trees out their windows heal faster and with less
complications. Children with ADHD show fewer
symptoms when they have access to nature. Exposure
to trees and nature aids concentration by reducing
mental fatigue. (Source: Tree People)
Trees enhance children’s play.

They are natural playthings, full of life, and as capable of stimulating a child’s imagination and sense of
wonder as the most expensive toy.

Trees bestow beauty, character, and identity on
a place. To come home to a green and shaded
community establishes a powerful sense of place.

The experience of traveling through the community
is immeasurably more pleasurable along tree-lined
streets. Distinctive plantings on major streets
also help with orientation, making the city more
“imageable” and therefore easier to navigate. Trees
enrich the aesthetic experience of the city, adding
pleasing shapes, colors, fragrance, texture, scale, and seasonal change.

Trees instill civic pride.

Citizens can feel proud of a city filled with beautiful trees. Tree planting programs allow citizens to
participate and work together to create a more
attractive city, fostering a sense of community.

Trees provide shade and reduce heat.

Trees are integral to fighting the effects of urban heat islands. In urban areas, shaded surfaces may be 20-45
degrees cooler and evapotranspiration can reduce
peak summer temperatures by 2-9 degrees.

Trees moderate wind.

When trees are planted strategically, they not only
reduce wind exposure but can reduce heating bills in
the winter by 2 to 8 percent.

Trees improve air quality and reduce pollution.

By producing oxygen and filtering airborne
particulates, trees help reduce air pollution. A tree’s production of oxygen replenishes the atmosphere
and dilutes pollutants. Airborne particulate pollution
is trapped on the surface of leaves, which act as
significant “scrubbers” or filters. In the United States alone, trees remove some 784,000 tons of pollution
annually.

Trees provide habitat for animals.

Supporting a variety of insects, birds, and mammals
with food and shelter, trees are a city’s prime medium
for attracting wildlife.

Trees improve water quality.

Leaves slow the impact of drops to reduce erosion and
surface runoff, while roots help filter stormwater to
improve groundwater quality and quantity.

Trees increase property values.

The beauty of a well-planted property and its
surrounding street and neighborhood can raise
residential property value by as much as 20 percent.

Trees help drive economic development.

Recent studies have revealed that people will travel
farther, pay more for goods and services, and visit
commercial districts more frequently—by an average
of 12 percent—when trees and landscaping are
present. Thus trees can help attract new businesses
and tourism.

Trees provide energy savings.

The cooling, sheltering effect of trees helps lower
energy use and bills.

Trees slow climate change.

By absorbing carbon dioxide through the processes
of photosynthesis, carbon is “sequestered” in the
biomass of the tree as long as the tree lives. A single large, healthy tree can remove greater than 300
pounds of carbon dioxide from the atmosphere every
year. The reduction in energy use resulting from trees
also decreases carbon production. Trees’ positive
impact on water quality & retention alleviates the
effects of droughts. All of these factors help stem the economic impacts of climate change.
4 SIGNAL HILL STREET TREE MASTER PLAN
plan). Factors considered include planting area
and tree size, power line friendliness, root
invasiveness, wind tolerance, and aesthetics.

Chapter 2 provides planting design guidelines,
species selection criteria, and the updated
tree palette. Chapter 3 includes procedures
for planting, pruning, and maintaining trees.

Chapter 4 outlines how to maintain and develop
the street tree inventory as a whole, including
budgeting and phasing, as well as analysis of
existing policy. Chapter 5 includes community
feedback as well as ways to continue to include
the community. There are different ways of
pursuing the goal of an increased street tree
canopy for the City of Signal Hill. This document
can be used by the department of public works
to rebuild the street tree population in the
most efficient and economic way possible, as
well as a manual for selecting, planting, and
maintaining the right tree in the right place.

1.1d How To Use This Document
This document is meant to provide a path
for the City of Signal Hill to restore, grow,
and maintain its street tree population. The
document includes important background
and contextual information, budget advice,
resources to pursue grants and funding,
planting and maintenance guidelines, a tree
palette and selection guide, and methods to
involve the public.

While street trees comprise only a small part
of the tree canopy, they have a huge impact
on heat and can greatly reduce the urban heat
island effect. Filling the nearly one thousand
vacant street tree sites in a methodical and
efficient manner will not only help keep the city
cool in the face of climate change, but help
grow the city’s tree canopy. This document
provides an updated tree palette that
considers the future of the climate as well as
practical input from city employees. Based on
feedback, native trees now make up 42% of the
recommended palette, whereas the 2010 Street
Tree Master Plan did not include any native
species.

All trees on the palette have lower water needs,
and they can be chosen based on the actual
conditions of their particular site, instead of
on a street-by-street basis (as with the 2010
Street trees in Beverly Hills, which has 35% canopy coverage (#canopygoals). Photo: City Plants SECTION 1: BACKGROUND 5

1.2a A Brief History of Signal Hill
Signal Hill’s first human population, the
Puvungna settlement of Tongva/Gabrielino
Indians, used the hilltop to signal their
neighbors on Catalina Island. Spanish settlers
called it “Loma Sental,” which became Signal
Hill in English. Under Spanish colonization,
Signal Hill fell under the jurisdiction of Rancho
Los Alamitos and Rancho Los Cerritos.

Throughout the 19th century, the land was used
for ranching and agriculture, including sheep
grazing by the Bixby family.

At the turn of the century, the hill was home to
mansions taking advantage of the panorama
offered. The surrounding land supported
many farms, including a large Japanese
community. However, the discovery of oil and
the enactment of the Alien Land Laws soon
replaced the farms and mansions with oil fields.

Royal Dutch Shell Oil Company hit a gusher on
June 3, 1921, at Alamitos Well #1, and Signal
Hill soon became a significant exporter of
petroleum. The land, meanwhile, became so
crowded with oil derricks that Signal Hill earned
the moniker “Porcupine Hill.”

1.2 Planning Context
A map of the Spanish Ranchos. Source: David Rumsey Map Collection 6 SIGNAL HILL STREET TREE MASTER PLAN
finally get its own zip code in July 2002 (until
then it shared one with Long Beach).

Today, Signal Hill boasts all kinds of businesses,
including those in the auto, healthcare and
tech industries, in addition to oil. The city itself
maintains a diverse population, beautiful parks,
and is heading toward a greener future.
two and injured eight. The fire burned for
two days and took the combined efforts of
the Signal Hill, Long Beach and LA County fire
departments to put out.

During the recession of the 1970s, the city
established the Signal Hill Development
Agency to focus on economic growth
and diversification from oil, as well as
environmental cleanup. Signal Hill also voted to
Though Signal Hill is completely enveloped
by the city of Long Beach, it voted for
incorporation in 1924 to avoid its neighbor’s oil
tax. The first mayor, Jessie Nelson, was also
one of the first female mayors in California.

With the success of oil, however, came
environmental repercussions. The town no
longer supported farmland, and the oil was
prone to explosions and spills with lasting
ecological damage. An explosion in 1958 killed
A view of Long Beach from Signal Hill, 1898. Source: Los Angeles Public Library 1958 Fire. Source: Los Angeles Public Library SECTION 1: BACKGROUND 7
“Porcupine Hill,” 1922. Source: Huntington Library
An oil gusher, c. 1925. Source: Huntington Library Signal Hill Oil Field. Source: Los Angeles Public Library 8 SIGNAL HILL STREET TREE MASTER PLAN

1.2b Pre-Columbian Ecology
Signal Hill’s most likely original ecology, before it
became farm and ranch land, was coastal sage
scrub and wet meadows. Situated between
the channelized beds of the Los Angeles and
San Gabriel rivers, Signal Hill is split by the
two watersheds. Before these two rivers were
channelized, their paths varied greatly from
season to season, forming braided streams
within wide channels. As the rivers approached
the Pacific Ocean, they would have formed
wetlands, supporting rich biodiversity. This
land, with its access to water and abundance
of wildlife, enabled the Tongva/Gabrielino
tribe to flourish here. Water from the rivers,
originating from the mountains to the north,
would have been rich in sediment and thus able
to support the farmland that later occupied the
location.

1.2c Natural Vegetation of Signal Hill
The vegetation in the wet meadow areas at the base of the hill would most likely have included grasses and wetland species like sedges and rushes as well as wildflowers. It would have supported minimal tree coverage, but shrubs like willow and mulefat. Riparian trees like cottonwoods, alders and sycamore might have grown at the edges, however. The hillside conditions of Signal Hill would have been home to a coastal sage scrub plant community. Plants that would have thrived there include sagebrush, buckwheat, and coyote brush. Coastal sage scrub would not have supported a large tree canopy like a forest, but a number of small trees / large shrubs like coast live oak, toyon, and lemonade berry would have provided shade. Plants such as sticky monkeyflower, lupines, sage, and encelia would have created pops of color. source: Travis Longcore, Beau MacDonald, Gary Stein, William Deverell, Philip J. Ethington. June 2020. USC Spatial Sciences Institute.

Tidal Marsh
Perennial Freshwater Pond
Alkali Meadow
Wet Meadow / Seasonal Wetland
Perennial Freshwater Wetland
Historic San Gabriel River Flows
San Gabriel River Historic
Wetlands
Chaparral
California Grasslands & Flowerfields
Coastal Sage Scrub
Freshwater Marsh
Lakes
Riparian Forest
Salt Marsh
Salt Marsh Meadows
Vernal Pools
Wet Meadow
Historic LA River Flows
Current Rivers & Streams
Potential Natural Vegetation of
the Los Angeles River Watershed
Figure 1.2.1: Historic Ecology of Signal Hill.

The two rivers framing Signal Hill would have looked very different before channelization. Photo: USGS
SECTION 1: BACKGROUND 9
Baccharis pilularis, coyote brush Lupinus succulentus, arroyo lupine Ribes speciosum, fuchsia-flowering gooseberry
Diplacus aurantiacus, sticky monkey flower
Encelia californica, bush sunflower
Rhus integrifolia, lemonade berry
Salvia leucophylla, purple sage Eriogonum fasciculatum, California buckwheat

1.2d Native Ecologies:

Coastal Sage Scrub
The Coastal Sage Scrub plant community grows
all along California’s coasts. Mild temperatures
and moisture from the ocean air allow for
softer leaves than the chaparral found further
inland and flowering plants year-round. Dry
weather and heat cause many plants to go
dormant in the later summer and fall, even
while others are blooming. Near canyons and
depressions that retain moisture, larger shrubs
and riparian trees can also be found.

Coastal Sage Scrub. Photo: US Fish & Wildlife Service
10 SIGNAL HILL STREET TREE MASTER PLAN
Photo: M. Lavin
Juncus bufonius, toad rush Bromus carinatus, California brome grass Carex praegracilis, clustered field sedge Lythrum californicum, common loosestrife Schoenoplectus californicus, California bulrush Salix exigua, sandbar willow

1.2e Native Ecologies: Wet Meadow
This ecosystem is characterized by grass,
sedges, rushes, and forbs which can all tolerate
seasonal inundation. They are often a buffer
between wetlands and other ecosystem types,
like coastal sage scrub. Because they are
dependent on water, they are usually located
near rivers (as with Signal Hill) or lakes.

Photo: J. Pawek
Photo: V. Reed Photo: K. Morse
Grassland alongside hills and a riparian corridor. Photo: California Native Grasslands Association Photo: K. Peters
SECTION 1: BACKGROUND 11
Platanus racemosa, western sycamore
Populus fremontii, Fremont cottonwood
Sceloporus occidentalis, western fence lizard
Alnus rhombifolia, white alder Quercus agrifolia, coast live oak Polioptila californica californica, coastal California gnatcatcher Papilio rutulus, western tiger swallowtail
Juglans californica, California walnut
Lynx rufus, bobcat
Megachile perihirta, western leafcutter bee
Sambucus nigra ssp. caerulea, blue elderberry
Rana draytonii, California red-legged frog
Calypte anna, Anna’s hummingbird

1.2f Native Ecologies: Trees & Animals
Both wet meadow and coastal sage scrub
plant communities would include some tree
species, especially given riparian conditions.

Additionally, they would support a wide variety
of animal life, including pollinators, birds,
reptiles, amphibians, and mammals, creating
great biodiversity.

Photo: E. Wu
Photo: D. Hoffman
Photo: T. Benson
Photo: USFW Photo: SMMNRA Photo: J. Valdez
Photo: R. Hannawacker Photo: E. Alverson Photo: P. Bryant 12 SIGNAL HILL STREET TREE MASTER PLAN
1” = 40,000’
0 20,000 40,000 N

1.2g Signal Hill’s Position in the Region
Signal Hill lies between two major freeways
(the 605 and the 710) and the rivers they follow
(the Los Angeles and the San Gabriel). It is
surrounded by the city of Long Beach, and is
situated at the southern end of Los Angeles
County, near the border of Orange County.
source: ESRI; LA County eGIS; CalFire, NOAA
Orange County Line
Freeways
Rivers
Signal Hill Border
Long Beach Border
Figure 1.2.2: Signal Hill's Position in the Region, 1:480,000 SECTION 1: BACKGROUND 13
Ports of Los Angeles & Long Beach
1” = 16,000’
0 8,000 16,000 N
source: ESRI; LA County eGIS; CalFire, NOAA
Signal Hill’s location close to the Pacific Ocean
and major infrastructure like the Ports of
Los Angeles and Long Beach and Long Beach
Airport provides Signal Hill with many economic
opportunities, but also has environmental
repercussions.

CalEnviroScreen uses government data to
map the effects of pollution on California
communities, charting the data by census
tract. It uses environmental, health, and
socioeconomic factors to compare different
areas. A higher score indicates a worse
pollution burden.1 CalFire and other state
agencies take this score into account when
awarding grants. The following pages show
CalEnviroScreen’s 2021 findings for Signal Hill
and the surrounding area.

Figure 1.2.3: Signal Hill's Position in the Region, 1:192,000 1 https://oehha.ca.gov/calenviroscreen/about-calenviroscreen 14 SIGNAL HILL STREET TREE MASTER PLAN
1” = 16,000’
0 8,000 16,000 N

1.2h Environmental Health
CalEnviroScreen Overall Score (Percentage)
The overall score takes into account both
environmental and socioeconomic factors
to compare communities, which are then are
ranked based on these elements. For example,
a score of 12% indicates a community fares
worse than only 12% of the state and is not
considered disadvantaged, while a score of 87%
indicates a community fares worse than 87% of
the state and is highly impacted by pollution.

The northwest section (Zone 1) of Signal Hill
scores 71% percent, the middle sections in
orange score 79%, and the yellow section
scores 56%, with a city average of 69%.
source: ESRI, CalEnviroScreen
0-10
10-20
20-30
30-40
40-50
50-60
60-70
70-80
80-90
90-100
Figure 1.2.4: CalEnviroScreen Overall Score
SECTION 1: BACKGROUND 15
1” = 16,000’
0 8,000 16,000 N
CalEnviroScreen Pollution Burden
This map depicts the potential exposures to
pollutants and the adverse environmental
conditions caused by pollution. It takes into
account factors like particulate matter, drinking
water contaminants, toxic releases from facilities,
cleanup sites, groundwater threats, and other
environmental hazards. The northwest section
(Zone 1) of Signal Hill scores 96% percent, the
middle sections in purple score 91%, and the pink
section scores 76%, with a city average of 88%.

These scores indicate that the city has a very high
pollution burden, higher than most of state. Trees
can help relieve many of these issues, by working
to clean the air and groundwater.
source: ESRI, CalEnviroScreen
0-10
10-20
20-30
30-40
40-50
50-60
60-70
70-80
80-90
90-100
Figure 1.2.5: CalEnviroScreen Pollution Burden
16 SIGNAL HILL STREET TREE MASTER PLAN
1” = 2,400’
0 1,200 2,400
N

1.3a The City of Signal Hill
Environmental and social conditions impact the
growth of trees and other vegetation, as well
as the planting and infrastructural strategies
that can provide the greatest benefits.

Understanding the context of the community
forest helps in developing the most appropriate
solutions for its sustainable management.

Signal Hill occupies 2.25 square miles within
the city of Long Beach and the Long Beach Oil
Field. The city straddles the 405 freeway and
sits just southwest of Long Beach Airport. The
2020 census population estimate is 11,848.

Its eponymous hill gives the city a unique
character and great views of the surrounding
ocean and mountains.

California experiences yearly seasonal drought
from mid-spring to mid-fall, as a continental
high pressure system keeps moist oceanic
weather systems well off-shore. When cooler
winter temperatures dissipate the high
pressure, a stream of winter storms flows down
from Alaska and Asia, leaving an average annual
precipitation in Signal Hill of 12 inches. During
years in which the high pressure system lingers,
winter storms can be reduced drastically,
leading to periods of sustained drought, such
as is occurring now. These conditions have
understandably put a strain on the community
forest.

1.3 Existing Conditions
source: City of Signal Hill
Figure 1.3.1: The City of Signal Hill, 1:28,800
SECTION 1: BACKGROUND 17
Signal Hill’s Mediterranean climate typically
requires plants that are adapted not only
to relatively low overall rainfall, but also to
the stress of regular summer dryness and
occasional long-term drought. In order to
increase the resiliency of the community
forest, ensure its long term benefits, and
reduce maintenance costs, trees and plants
that have low to very low water needs should
be prioritized. However, even these species
need periodic watering during the first two or
three summers until their root systems are
well-developed.

Strong winds sometimes accompany winter
storms, while dry, powerful Santa-Ana winds
come in from desert regions to the east and
south. Understanding wind patterns in relation
to a particular site will indicate whether a
particularly wind-tolerant tree species should
be selected.

Signal Hill is located within Sunset Climate Zone
22 and USDA Plant Hardiness Zone 10b. Sunset
describes this zone as quite mild, and freezing
weather is extremely rare, though temperatures
can occasionally fall into the 25-28°F range.

Because it freezes so rarely, deciduous woody
plants do not thrive here, but subtropical plants
can as long as they are protected from the
occasional frost.

The conditions at a specific planting site
can vary greatly depending on its immediate
surroundings. These locational conditions
are referred to as the microclimate, which is
influenced by topography (aspect and slope),
structures, pavement, and existing vegetation.

As a city with a long history of oil production,
pollution is another important factor to
consider for the health of Signal Hill’s tree
canopy. This consideration is a two-way
street: trees may not thrive in an area
with contaminated soil or water; however,
certain species can actually help to clean
said water and soil in a process known
as phytoremediation. Plants draw up
contaminants through their roots and either
store them or break them down into less
harmful components, regardless removing the
contaminants from the soil and water. More
information on phytoremediation can be found
on page 66.

Finally, the city itself needs to ensure that
critical infrastructure like water and sewer
lines, hydrants, and power lines are protected.

Trees can cause costly damage to this
infrastructure if not planted and maintained
with careful consideration. The city must also
maintain the current tree canopy as it seeks to
expand it.

Figure 1.3.2: Signal Hill Average Temperature &
Precipitation. Source: National Weather Service
Figure 1.3.3: Signal Hill Wind Direction.

Source: Midwestern Regional Climate Center
Signal Hill Wind Rose
Generated from Long Beach Daugherty Field, 2002-2022

1.3 - 4 4 - 8 8 - 13 13 - 19 19 - 25 25 + Frequency (%) Wind Speed (mph)
N
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
NW
NNW
0%
5%
source: Midwestern Regional Climate
Signal Hill Wind Rose
Generated from Long Beach Daugherty Field, 2002-2022

1.3 - 4 4 - 8 8 - 13 13 - 19 19 - 25 25 + Frequency (%) Wind Speed (mph)
N
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
NW
NNW
0%
5%
source: Midwestern Regional Climate
18 SIGNAL HILL STREET TREE MASTER PLAN
Coastal Plain of Los Angeles - West Coast
Coastal Plain of Los Angeles - Central

1.3b Topography & Groundwater
The shape of the land can affect air drainage,
resulting in warmer zones on sloped ground
and cool areas in basins or where air flow is
stilled. Slopes may also create wind. The angle
of the land in relation to the sun is important,
with south- and west-facing slopes receiving
the most direct sunlight and therefore being
significantly hotter and dryer than the cool,
moist microclimates of north- or east-facing
slopes. Additionally, slope can impact the
availability of water to vegetation. Quick runoff of water from steep slopes can contribute to excessively dry soil, while low spots collect
run-off and may therefore be wetter than the
surrounding soil. Topography also dictates
where water flows, dividing Signal Hill into
the Los Angeles River Watershed / West
Coast Groundwater Basin and the San Gabriel
River / Central Groundwater Basin. Trees
can be instrumental in maintaining healthy
watersheds.
source: ESRI, LARIAC
Elevation
Contour Line (50ft)
Coastal Plain of Los Angeles -
Central Groundwater Basin
Coastal Plain of Los Angeles -
West Coast Groundwater Basin
High
Low
1” = 2,400’
0 1,200 2,400 N
Figure 1.3.4: Topography & Groundwater
SECTION 1: BACKGROUND 19
Dominguez Channel
Watershed
Seal Beach
Watershed
San Gabriel River
Watershed
Los Angeles
River
Watershed
Santa Monica
Bay Watershed
Figure 1.3.6: Watersheds of the Signal Hill Area

1.3c Oil Infrastructure
Signal Hill’s long history of oil production has
been an economic boon but an environmental
burden. A large portion of the city hosts
either active or plugged wells. These sites
are usually cleared of vegetation, reducing
the tree canopy. Wells that are not properly
plugged and abandoned can remain a possible
hazard, potentially leaking fluids and gases and
interfering with future surface development.
1 Additionally, fracking at injector well sites
uses large amounts of water to help release
the oil. This water can pollute the groundwater
basins and river watersheds and may require
treatment before disposal or reuse.

Signal Hill’s position among two watersheds
and groundwater basins makes it particularly
important to clean any water entering these
vital resources, particularly in times of drought.
1 https://www.eia.gov/energyexplained/oil-and-petroleum-products/oil-and-theenvironment.php source: ESRI, WellSTAR, Geologic Energy Management Division, California Department of Conservation Active Oil & Gas
Active Injector
Canceled Oil & Gas
Idle Oil & Gas
Idle Injector
Plugged Oil & Gas
Plugged Injector
Plugged Multipurpose
1” = 2,400’
0 1,200 2,400
N
Figure 1.3.5: Oil Infrastructure
20 SIGNAL HILL STREET TREE MASTER PLAN
1” = 2,400’
0 1,200 2,400 N

1.3d Urban Heat Index
& Current Tree Canopy
Urban heat islands are urbanized areas that
experience higher temperatures and pollution
than their rural counterparts, creating negative
health effects. The Index is calculated as a
positive temperature differential over time
between an urban census tract and nearby
upwind rural reference points at a height of
two meters above ground level, where people
experience heat. Heat islands are created by
a combination of heat-absorptive surfaces
(such as dark pavement and roofing), heatgenerating activities (such as engines and generators) and the absence of vegetation
(which provides evaporative cooling).1
Stands of existing trees near a planting site
can block wind or create shade. Large areas
of vegetation reverse the effect of heat
islands by absorbing sunlight and by releasing
moisture into the air by transpiration from the
leaves, cooling the surroundings like a huge air
conditioner. Airborne moisture from ocean fog
or other sources also tends to condense on
the surfaces of leaves and needles, causing a
wetter, cooler microclimate. As the map shows,
Signal Hill’s existing tree canopy helps mitigate
the urban heat island effect.
1 https://calepa.ca.gov/climate/urban-heat-island-index-for-california/understanding-theurban-heat-island-index/ source: ESRI, The Trust for Public Land, Descartes Labs, USGS, USDA Forest Service, California Department of Forestry and Fire Protection Tree Canopy
Urban Heat Index
High
Low
Figure 1.3.7: Urban Heat Index & Current Tree Canopy
SECTION 1: BACKGROUND 21
1” = 16,000’
0 8,000 16,000 N

1.3e Tree Canopy Percentage
by Census Tract
Currently, Signal Hill’s tree canopy percentage
(the proportion of land surface covered by tree
tops) ranges from 10-16%.2 The Street Tree
Master Plan aims to help grow the tree canopy
overall, as well as improve shade equity.
2 https://www.treepeople.org/los-angeles-county-tree-canopy-map-viewer/ source: ESRI, TreePeople, Loyola Marymount University Center of Urban Resilience (CURes), Los Angeles Region Imagery Acquisition Consortium, University of Vermont Spatial Analysis Lab, SavATree Consulting Group, Los Angles Urban Center, Chapman University Existing Tree Canopy Percentage by Census Tract
18-20
20-24
24-29
29-36
36-49
49-68
0-4
4-8
8-10
10-13
13-15
15-18
Figure 1.3.8: Tree Canopy Percentage by Census Tract
22 SIGNAL HILL STREET TREE MASTER PLAN
1” = 2,400’
0 1,200 2,400 N

1.3f Tree Equity Score
The Tree Equity Score (TES) is calculated
based on how much tree canopy and surface
temperature align with income, employment,
race, age and health factors in the U.S.1 A
canopy goal is calculated for a neighborhood,
and then the actual canopy is subtracted from
that, giving a canopy gap. A priority index takes
into account income, employment, race, age,
health, and Urban Heat Island severity. These
numbers are combined to create the TES. A
lower TES indicates a higher priority for planting
trees in order to close the tree canopy gap.2
The map at left shows that Signal Hill should
focus tree planting in the western and northern
areas of the city (Zones 1 & 3) to improve
shade equity. Zone 4 should be a lower priority.

American Forests, the organization behind the
Tree Equity Score, has created a Tree Equity
Catalyst Fund to help cities achieve tree
equity. In the future, perhaps Signal Hill could
participate in this program as it adds more
cities to its fund.
1 https://www.treeequityscore.org/about/
2 https://www.treeequityscore.org/methodology/
source: ESRI, American Forests
30 100
Tree Equity Score
Figure 1.3.9: Tree Equity Score
SECTION 1: BACKGROUND 23
1” = 2,400’
0 1,200 2,400 N

1.3g Public Works & Power
Infrastructure
The City of Signal Hill Public Works department
divides the city into 4 quadrants to determine
their tree trimming and maintenance schedule.

The department must maintain water lines as
well as meter boxes and fire hydrants. Tree
roots can damage subterranean lines in their
quest for water, and are particularly likely
to damage sewer laterals. Therefore careful
consideration must be given when planting new
trees in the vicinity of any of this ubiquitous
infrastructure.

Each species must be appropriate for its
location. Trees with water-seeking roots should
not be placed near water or sewer lines, and
tall trees should not be planted under power
lines. Street trees should be planted at an
appropriate distance to meter boxes and
fire hydrants. Crucially, each of the nearly
one thousand vacant tree wells, visible on
the following map, should be filled with an
appropriate tree.
source: City of Signal Hill, Southern California Edison Water Mains
Sewer Lines
Major Power Lines
Power Lines
(above & below GL)
Fire Service
Hydrant Service
Other Service
Meter Addresses
Hydrants
Zone 1
Zone 2
Zone 3
Zone 4
Figure 1.3.10: Public Works & Power Infrastructure
24 SIGNAL HILL STREET TREE MASTER PLAN
Trees and oil derrick near Hilltop Park. Photo: G. Castriotta SECTION 1: BACKGROUND 25
1” = 2,400’
0 1,200 2,400
N

1.3h Current Street Tree Species Map
source: City of Signal Hill
Lavender Trumpet Tree
Carob
Pecan
Italian Cypress
Brisbane Box
Modesto Ash*
Southern Magnolia
Queen Palm
African Sumac
Lemon
Carolina Red Cherry
Weeping Bottlebrush
Bronze Loquat
Frangipani
Crape Myrtle Queensland Umbrella Tree
Aleppo Pine
Lemon Bottlebrush
Carrotwood
Jacaranda
Weeping Fig
Brush Cheerry
New Zealand Christmas Tree
Glossy Privet
Date Palm Red Gum
Alii Fig
Lemon-Scented Gum
Cherimoya
Pink Crape Myrtle
Japanese Black Pine
Western Redbud*
Cajeput Tree
Gold Medallion Tree
Sugar Gum
Red Ironbark
American Sweetgum
London Plane
Java Plum
Windmill Palm
Stump
Bolded species are 10 most common
California Fan Palm*
Norfolk Island Pine
Goldenrain Tree
Sweet Bay
Desert Gum
Arizona Ash*
Maidenhair Tree
Chinaberry
King Palm
Yew Pine
Vacant Site
* Indicates native species
California Pepper
Olive
Guava
Tipu
Rusty-leaf Fig
Australian Flame Tree
Malus (Apple) Species
Chinese Elm Tree
Pink Trumpet Tree
California Sycamore*
Orange
Hackberrry
Eastern Redbud
Sawtooth Zelkova
Australian Willlow
Mediterranean Fan Palm
Chinese Flame Tree
Primrose Tree
Camphor Tree
Ornamental Pear
Holly Oak
Edible Loquat
Shamel Ash
Bottle Tree
Silver Dollar Gum
Chinese Pistache
Purple Orchid Tree
Canary Island Date Palm
Palm
Honey Locust
Evergreen Pear
Siberian Elm
Brazilian Pepper
Mexican Fan Palm
Flaxleaf Paperbark
Silver Mountain Gum
Purple-Leaf Plum
Canary Island Pine
Palo Verde
Indian Laurel Fig
Tupidanthus
Fern Pine
Silk Tree
Figure 1.3.11: Current Street Tree Species Map
26 SIGNAL HILL STREET TREE MASTER PLAN
source: City of Signal Hill
1” = 1,200’
0 600 1,200
N
1 2
3 4
Zone 1
Lavender Trumpet Tree
Carob
Pecan
Italian Cypress
Brisbane Box
Modesto Ash*
Southern Magnolia
Queen Palm
African Sumac
Lemon
Carolina Red Cherry
Weeping Bottlebrush
Bronze Loquat
Frangipani
Crape Myrtle Queensland Umbrella Tree
Aleppo Pine
Lemon Bottlebrush
Carrotwood
Jacaranda
Weeping Fig
Brush Cheerry
New Zealand Christmas Tree
Glossy Privet
Date Palm Red Gum
Alii Fig
Lemon-Scented Gum
Cherimoya
Pink Crape Myrtle
Japanese Black Pine
Western Redbud*
Cajeput Tree
Gold Medallion Tree
Sugar Gum
Red Ironbark
American Sweetgum
London Plane
Java Plum
Windmill Palm
Stump
Bolded species are 10 most common
California Fan Palm*
Norfolk Island Pine
Goldenrain Tree
Sweet Bay
Desert Gum
Arizona Ash*
Maidenhair Tree
Chinaberry
King Palm
Yew Pine
Vacant Site
* Indicates native species
California Pepper
Olive
Guava
Tipu
Rusty-leaf Fig
Australian Flame Tree
Malus (Apple) Species
Chinese Elm Tree
Pink Trumpet Tree
California Sycamore*
Orange
Hackberrry
Eastern Redbud
Sawtooth Zelkova
Australian Willlow
Mediterranean Fan Palm
Chinese Flame Tree
Primrose Tree
Camphor Tree
Ornamental Pear
Holly Oak
Edible Loquat
Shamel Ash
Bottle Tree
Silver Dollar Gum
Chinese Pistache
Purple Orchid Tree
Canary Island Date Palm
Palm
Honey Locust
Evergreen Pear
Siberian Elm
Brazilian Pepper
Mexican Fan Palm
Flaxleaf Paperbark
Silver Mountain Gum
Purple-Leaf Plum
Canary Island Pine
Palo Verde
Indian Laurel Fig
Tupidanthus
Fern Pine
Silk Tree
405
California AveOrange Ave
Spring St
28th St
E Willow St
Figure 1.3.12: Current Street Tree Species Map, Zone 1
SECTION 1: BACKGROUND 27
1” = 1,200’
0 600 1,200
N
1 2
3 4
Zone 2
source: City of Signal Hill
Lavender Trumpet Tree
Carob
Pecan
Italian Cypress
Brisbane Box
Modesto Ash*
Southern Magnolia
Queen Palm
African Sumac
Lemon
Carolina Red Cherry
Weeping Bottlebrush
Bronze Loquat
Frangipani
Crape Myrtle Queensland Umbrella Tree
Aleppo Pine
Lemon Bottlebrush
Carrotwood
Jacaranda
Weeping Fig
Brush Cheerry
New Zealand Christmas Tree
Glossy Privet
Date Palm Red Gum
Alii Fig
Lemon-Scented Gum
Cherimoya
Pink Crape Myrtle
Japanese Black Pine
Western Redbud*
Cajeput Tree
Gold Medallion Tree
Sugar Gum
Red Ironbark
American Sweetgum
London Plane
Java Plum
Windmill Palm
Stump
Bolded species are 10 most common
California Fan Palm*
Norfolk Island Pine
Goldenrain Tree
Sweet Bay
Desert Gum
Arizona Ash*
Maidenhair Tree
Chinaberry
King Palm
Yew Pine
Vacant Site
* Indicates native species
California Pepper
Olive
Guava
Tipu
Rusty-leaf Fig
Australian Flame Tree
Malus (Apple) Species
Chinese Elm Tree
Pink Trumpet Tree
California Sycamore*
Orange
Hackberrry
Eastern Redbud
Sawtooth Zelkova
Australian Willlow
Mediterranean Fan Palm
Chinese Flame Tree
Primrose Tree
Camphor Tree
Ornamental Pear
Holly Oak
Edible Loquat
Shamel Ash
Bottle Tree
Silver Dollar Gum
Chinese Pistache
Purple Orchid Tree
Canary Island Date Palm
Palm
Honey Locust
Evergreen Pear
Siberian Elm
Brazilian Pepper
Mexican Fan Palm
Flaxleaf Paperbark
Silver Mountain Gum
Purple-Leaf Plum
Canary Island Pine
Palo Verde
Indian Laurel Fig
Tupidanthus
Fern Pine
Silk Tree
405
Orange Ave
Spring St
E Willow St
28th St
Cherry Ave
Figure 1.3.13: Current Street Tree Species Map, Zone 2
28 SIGNAL HILL STREET TREE MASTER PLAN
source: City of Signal Hill
1” = 1,200’
0 600 1,200
N
1 2
3 4
Lavender Trumpet Tree
Carob
Pecan
Italian Cypress
Brisbane Box
Modesto Ash*
Southern Magnolia
Queen Palm
African Sumac
Lemon
Carolina Red Cherry
Weeping Bottlebrush
Bronze Loquat
Frangipani
Crape Myrtle Queensland Umbrella Tree
Aleppo Pine
Lemon Bottlebrush
Carrotwood
Jacaranda
Weeping Fig
Brush Cheerry
New Zealand Christmas Tree
Glossy Privet
Date Palm Red Gum
Alii Fig
Lemon-Scented Gum
Cherimoya
Pink Crape Myrtle
Japanese Black Pine
Western Redbud*
Cajeput Tree
Gold Medallion Tree
Sugar Gum
Red Ironbark
American Sweetgum
London Plane
Java Plum
Windmill Palm
Stump
California Fan Palm*
Norfolk Island Pine
Goldenrain Tree
Sweet Bay
Desert Gum
Arizona Ash*
Maidenhair Tree
Chinaberry
King Palm
Yew Pine
* Indicates native species
California Pepper
Olive
Guava
Tipu
Rusty-leaf Fig
Australian Flame Tree
Malus (Apple) Species
Chinese Elm Tree
Pink Trumpet Tree
California Sycamore*
Orange
Hackberrry
Eastern Redbud
Sawtooth Zelkova
Australian Willlow
Mediterranean Fan Palm
Chinese Flame Tree
Primrose Tree
Camphor Tree
Ornamental Pear
Holly Oak
Edible Loquat
Shamel Ash
Bottle Tree
Silver Dollar Gum
Chinese Pistache
Purple Orchid Tree
Canary Island Date Palm
Palm
Honey Locust
Evergreen Pear
Siberian Elm
Brazilian Pepper
Mexican Fan Palm
Flaxleaf Paperbark
Silver Mountain Gum
Purple-Leaf Plum
Canary Island Pine
Palo Verde
Indian Laurel Fig
Tupidanthus
Fern Pine
Silk Tree
Zone 3
Figure 1.3.14: Current Street Tree Species Map, Zone 3
Cherry Ave
E Willow St Orange Ave
California Ave
E Hill St
Burnett St
Signal Hill
Park
Hilltop
Park
SECTION 1: BACKGROUND 29
source: City of Signal Hill
19thSt
1” = 1,200’
0 600 1,200 N
1 2
3 4
Lavender Trumpet Tree
Carob
Pecan
Italian Cypress
Brisbane Box
Modesto Ash*
Southern Magnolia
Queen Palm
African Sumac
Lemon
Carolina Red Cherry
Weeping Bottlebrush
Bronze Loquat
Frangipani
Crape Myrtle Queensland Umbrella Tree
Aleppo Pine
Lemon Bottlebrush
Carrotwood
Jacaranda
Weeping Fig
Brush Cheerry
New Zealand Christmas Tree
Glossy Privet
Date Palm Red Gum
Alii Fig
Lemon-Scented Gum
Cherimoya
Pink Crape Myrtle
Japanese Black Pine
Western Redbud*
Cajeput Tree
Gold Medallion Tree
Sugar Gum
Red Ironbark
American Sweetgum
London Plane
Java Plum
Windmill Palm
Stump
Bolded species are 10 most common
California Fan Palm*
Norfolk Island Pine
Goldenrain Tree
Sweet Bay
Desert Gum
Arizona Ash*
Maidenhair Tree
Chinaberry
King Palm
Yew Pine
Vacant Site
* Indicates native species
California Pepper
Olive
Guava
Tipu
Rusty-leaf Fig
Australian Flame Tree
Malus (Apple) Species
Chinese Elm Tree
Pink Trumpet Tree
California Sycamore*
Orange
Hackberrry
Eastern Redbud
Sawtooth Zelkova
Australian Willlow
Mediterranean Fan Palm
Chinese Flame Tree
Primrose Tree
Camphor Tree
Ornamental Pear
Holly Oak
Edible Loquat
Shamel Ash
Bottle Tree
Silver Dollar Gum
Chinese Pistache
Purple Orchid Tree
Canary Island Date Palm
Palm
Honey Locust
Evergreen Pear
Siberian Elm
Brazilian Pepper
Mexican Fan Palm
Flaxleaf Paperbark
Silver Mountain Gum
Purple-Leaf Plum
Canary Island Pine
Palo Verde
Indian Laurel Fig
Tupidanthus
Fern Pine
Silk Tree
Zone 4
Figure 1.3.15: Current Street Tree Species Map, Zone 4
Signal Hill
Park
Hilltop
Park
Cherry Ave
E Willow St
Redondo Ave
Junipero Ave
Temple Ave
Pacific Coast Hwy
30 SIGNAL HILL STREET TREE MASTER PLAN

1.4b Tree Taxonomy
Tree Families
The inventory of 2,859 live trees is composed
of 29 families of trees. The five most
represented families are Sapindaceae at 16
percent, Arecaceae at 16 percent, Ulmaceae
at 15 percent, Myrtaceae at 15 percent, and
Anacardiaceae at eight percent.

A commonly used guideline for managing
urban tree populations is that no family should
represent more than 30 percent of the tree
population. The street tree population in Signal
Hill currently complies with this guideline.

Tree Genera
The inventory of 2,859 live trees is composed
of 61 genera of trees. The five most
represented genera are Ulmus at 15 percent,
Washingtonia at 10 percent, Koelreuteria at nine
percent, Cupaniopsis at seven percent, and
Corymbia at seven percent. A commonly used
guideline for managing urban tree populations
is that no genus should represent more than 20

1.4 Current Street Tree
Conditions

1.4a Snapshot of Signal Hill Street Trees
The City of Signal Hill manages its tree data in
Arbor Access, a proprietary database of West
Coast Arborists (WCA), the company which
maintains the city's street trees. The exported
data, from July 2022, contains 2,859 live trees,
20 dead trees, 28 stumps, and 971 vacant
sites where trees can potentially be planted.

The data also includes records of 1,075 trees
removed in the years 1998 to 2022.
percent of the tree population. The street tree
population in Signal Hill currently complies with
this guideline.

Tree Species
The inventory of 2,859 live trees is composed
of 88 species of trees. The five most
represented species are Chinese elm (Ulmus
parvifolia) at 15 percent, Mexican fan palm
(Washingtonia robusta) at 10 percent,
Chinese flame tree (Koelreuteria bipinnata)
at seven percent, carrotwood (Cupaniopsis
Table 1 Street Tree Numbers & Value
Live Trees 2,859
Replacement Value $15.7 million
Table 4 Top 5 Tree Families
Sapindaceae 6%
Arecaceae 16%
Ulmaceae 15%
Myrtaceae 15%
Anacardiaceae 8%
Table 5 Top 5 Tree Genera
Ulmus 15%
Washingtonia 10%
Koelreuteria 9%
Cupaniopsis 7%
Corymbia 7%
Table 6 Top 5 Tree Species
Ulmus parvifolia Chinese Elm 15%
Washingtonia
Robusta
Mexican Fan
Palm
10%
Koelreuteria
bipinnata
Chinese Flame
Tree
7%
Cupaniopsis
anacardioides
Carrotwood 7%
Corymbia
citriodora
Lemon-Scented
Gum
7%
Table 2 Species Diversity
Number of Species 88
Prevalence of Top Ten Species 63%
Species Exceeding 10% 1
Table 3 Vacant Sites
Vacant Sites 1,019
Stocking Level 74%
SECTION 1: BACKGROUND 31
anacardioides) at seven percent, and lemonscented gum (Corymbia citriodora) at seven percent. A commonly used guideline for
managing urban tree populations is that
no species should represent more than 10
percent of the tree population. The street
tree population in Signal Hill currently does
not comply with this guideline as Chinese elm
trees represent 15 percent of the population.

One strategy to bring the Chinese elm species
to 10 percent or less of the population is to
temporarily or permanently remove this species
from the planting palette so that future street
tree plantings increase the populations of other
species.

Photo: ASU
Photo: D. Gress
Washingtonia Robusta, Mexican Fan Palm
Ulmus parvifolia, Chinese Elm Cupaniopsis anacardioides, Carrotwood Koelreuteria bipinnata, Chinese Flame Tree
Corymbia citriodora, Lemon-Scented Gum
32 SIGNAL HILL STREET TREE MASTER PLAN
Photo: B. Magic Photo: J. Vhertum

1.4c Native Tree Species
Of the 2,859 live trees in the inventory, 18 of
the trees are a native California species. The
native quantities and species in the inventory
are eight Arizona ash (Fraxinus velutina), six
western redbud (Cercis occidentalis), two
western sycamore (Platanus racemosa), one
California fan palm (Washingtonia filifera), and
one Palo verde (Parkinsonia florida). These 18
native trees represent less than one percent
of the street tree inventory.

Less than 1% of Signal Hill’s trees are native to California.

Figure 1.4.1: Native Tree Population. Out of the 100 trees in the diagram above, only one would be native (indicated in red and spotlighted) in Signal Hill's current street tree population.

Arizona Ash
Fraxinus velutina
Western Redbud
Cercis Occidentalis
Western Sycamore
Platanus racemosa
California Fan Palm
Washingtonia filifera
Palo Verde
Parkinsonia florida
Photo: G. Castriotta
SECTION 1: BACKGROUND 33
General strategies for improving the size
class distribution of the Signal Hill street tree
population are to maintain existing trees
so they continue to grow and increase the
populations of the larger diameter size classes
as well as to plant new trees consistently
over time to add to the smaller diameter size
classes.

Tree Height
Tree height is another common method of
quantifying the size of trees in a population.

Arbor Access database records tree height
data in terms of height classes in increments
of 15 feet. The three most represented height
classes together comprise 96 percent of the
inventory and include 15-30 feet at 60 percent,
30-45 feet at 26 percent, and 45-60 feet at 10
percent.

1.4d Tree Size Classifications
Trunk Diameter
A common method of measuring tree size is
Diameter at Standard Height (DSH), which
is the measurement of trunk diameter at
54 inches above grade. The Arbor Access
database records DSH data in terms of DSH
size classes in increments of 6 inches. The
three most represented DSH classes together
comprise 97 percent of the inventory and
include 7-12 inches at 39 percent, 13-18 inches
at 36 percent, and 19-24 inches at 22 percent.

A resilient tree population is one with trees
distributed across many size classes.

General strategies for improving the size
class distribution of the Signal Hill street
tree population are the same as mentioned

4.5’
19 -24”
13 -18”
7 -12”
22% 39%
36%
Trunk Diameter
3%
45 - 60’
15 -30’
30 -45’
60%
26%
10%
Tree Height
4%
Trunk Diameter
Tree Height Figure 1.4.3: Diameter at Standard Height. The circumference of the tree's trunk is measured at 4.5'
above the ground.

Figure 1.4.2: Trunk Diameter Distribution Chart
Figure 1.4.4: Tree Height Distribution Chart
34 SIGNAL HILL STREET TREE MASTER PLAN
in the trunk diameter section, which includes
maintaining existing trees so they continue
to grow and increase the populations of the
larger diameter size classes as well as planting
new trees consistently over time to add to the
smaller diameter size classes.

1.4e West Coast Arborists (WCA)
Recommendations & Categorizations
The tree database contains a field titled
“Recommended”. For trees lacking significant
structural defects and lacking significant health
conditions, WCA seems to use “Grid/ Routine
Trim” as a default recommendation, and this
recommendation is listed for 96 percent of
the live inventory. The recommendation “TrimPoorly Structured” is listed for two percent of the live tree inventory. Recommendations
involving tree removal are listed for two
percent of the live tree inventory. Finally, the
recommendation “Small Tree Maintenance” is
listed for less than one percent of the live tree
inventory.

Tree Condition
The database contains data on the assessed
condition of each live tree. The condition
classes are good, fair, poor, N/A. The recorded
conditions of the inventoried live trees show
a condition of good for 80 percent, fair for 14
percent, poor for five percent, N/A for less
than one percent, and three trees do not have
a recorded condition. The general goal is to
maintain as much of the inventory as possible
in the condition class of good.
recommendation of Grid/ Routine Trim, 15 have
the recommendation Trim-Poorly Structured,
and 41 have a recommendation involving
removal. These 155 trees are candidates
for assessment of retention/ removalreplacement.

Site Type
Arbor Access has a data field labeled “Parkway
Type” that describes the type of site in which
a tree is growing. Of the 2,859 live trees,
52 percent are Parkway, 23 percent are Tree
Well, 10 percent are Other, ten percent are
Monolithic, five percent are Median, and three
trees do not have a recorded parkway type.

Trees in the poor category are candidates for
a cost benefit assessment looking at if the
condition of the tree can be improved, and
if so, what are the costs and benefits. For
poor condition trees whose condition cannot
be improved, or whose condition can only
be improved at a relatively high cost, tree
removal and replacement may be warranted.

Of the 155 trees in poor condition, 99 have the
N/A
Tree Condition
80%
14%
5% Good
Fair
Poor
Site Type
52%
10%
10%
10%
5%
Parkway
Tree Well
Others
Monolithic
Median
Tree Condition
Site Type
Figure 1.4.5: Tree Condition Chart
Figure 1.4.6: Site Type Chart
SECTION 1: BACKGROUND 35
Trees Removed
Arbor Access data shows that in a period of 24
years (from August 1998 to August 2022) 1,224
trees were removed. On average, Signal Hill
removed 51 trees per year during this 24-year
period. The most trees removed in a calendar
year was 92 trees in 2003, and the fewest trees
removed in a calendar year was 15 in 2012.

Looking at tree genera with a quantity of 50
or more in the inventory, the genera with the
highest relative percentages of removals were
Ficus at 62 percent, Eucalyptus at 61 percent,
Pyrus at 36 percent, Liquidambar at 34 percent,
Melaleuca at 33 percent, Magnolia at 32 percent,
and Bauhinia at 31 percent (Table 7).

Dead Trees
The street tree inventory data from Arbor
Access contains 15 trees with a recommended
category of “Plant,” another three trees
with a status of “Dead,” and two trees with
a recommended category of “Removal-Dead
Tree.” These 20 dead trees are not included
in the live tree data in the previous sections.

These trees should be removed as soon as
possible.

Vacant Sites
The inventory in Arbor Access includes 971 tree
sites listed as a “Vacant Site”, meaning neither
a tree nor stump exists at that site; however, a
tree could be planted at that site. A vacant site
is often a site that previously had a tree, but
the tree and stump have been removed. The
street tree inventory contains 971 vacant sites.

The additional tree locations of 20 dead trees
and 28 stumps can quickly be converted into
vacant sites, for a total of 1,019 planting sites
without a live tree. Given these numbers, the
current street tree stocking level is 74 percent.

Of the 971 vacant sites, the site quantities
and types are 727 Parkway, 164 Tree Well, 32
Monolithic, 30 Median, 15 Other, and three
records had a blank site type. The map of
vacant sites will function as a helpful tool in
creating a planting plan and planting strategies.

Table 8 Top Species Removed
Ulmus parvifolia Chinese Elm 81
Corymbia
citriodora
Lemon-Scented
Gum
65 Ficus benjamina Weeping Fig 60
Koelreuteria
bipinnata
Chinese Flame
Tree
56 Washingtonia
Robusta
Mexican Fan
Palm
56 Ficus microcarpa
‘nitida’
Indian Laurel Fig 55
Liquidambar
styraciflua
Sweet Gum 53
Cupaniopsis
anacardioides
Carrotwood 51
Table 7 Percent of Trees Removed by Genera
Ficus 62%
Eucalyptus 61%
Pyrus 36%
Liquidambar 34%
Melaleuca 33%
Magnolia 32%
Bauhinia 31%
Tree Well Status
74%
25%
Stump or Dead
Living Tree
Vacant
Site Status
Figure 1.4.7: Site Status Chart
36 SIGNAL HILL STREET TREE MASTER PLAN
The species with the highest absolute
quantities removed (Table 8, previous page)
were 81 Chinese elm (Ulmus parvifolia), 65
lemon-scented gum (Corymbia citriodora),
60 weeping fig (Ficus benjamina), 56 Chinese
flame tree (Koelreuteria bipinnata), 56
Mexican fan palm (Washingtonia robusta), 55
Indian laurel fig (Ficus microcarpa ‘nitida’), 53
sweet gum (Liquidambar styraciflua), and 51
carrotwood (Cupaniopsis anacardioides).

For the 1,224 tree removals, the DSH at the
time of tree removal ranged from zero to 58
inches. Of these 1,224 trees, 62 percent of the
records did not have a recorded DSH class. The
DSH classes with the highest percentages of
removals were 7-12 inches at 16 percent and
13-18 inches at 12 percent. The tree height at
time of tree removal ranged from zero to 75
feet. Of these 1,224 trees, 61 percent of the
records did not have a recorded DSH class. The
height classes with the highest percentages
of removals were 15-30 feet at 19 percent and
1-15 feet at 8 percent.

1.4f Benefits of Signal Hill’s Street Trees
The i-Tree Eco application was used to
determine the benefits provided by the street
trees in Signal Hill. The replacement value for
the current street tree inventory is $15.7million.

Currently, the inventory stores 1,674 tons of
carbon, which is a benefit of $285,000, shown
in Table 14.

City-Wide Tree Canopy
The i-Tree Canopy application was used to
determine the city-wide tree canopy for Signal
Hill based on 100 random sampling locations.

This canopy assessment includes all land cover
in Signal Hill, both public and private. The tree/
shrub cover class was found to be 20.59 percent
with a standard error of ± 4.00. Benefits showing
the amount of carbon captured each year by the
city's street trees based off i-Tree calculations
are shown in Table 10. This tree/shrub canopy
cover value of 20.59 percent is slightly higher
than two GIS-based sources, from the USDA1 and
Tree People.2 . Those GIS datasets used analysis
of LiDAR and imagery to determine a canopy
1 https://www.fs.usda.gov/detailfull/r5/communityforests/?cid=fseprd647442&width=full 2 https://www.treepeople.org/los-angeles-county-tree-canopy-map-viewer/ Ficus benjamina, Weeping Fig
Ficus microcarpa ‘nitida,’ Indian Laurel Fig
Table 9 Benefits of Street Trees
Street Tree Replacement Value $15,700,000
Carbon Sequestration 1,674 tons
Economic Value $285,000
SECTION 1: BACKGROUND 37
coverage percent. Those sources put Signal
Hill's canopy cover between 10 and 16%. If we
estimate it to be around 14% and thus 75% of the
21% value from iTree, the updated benefits can
be calculated as shown in Table 11. Additional
tree canopy benefits are shown in Tables 12 &
13, showing the overall stored carbon value to
be between 1.31 and 1.75 million dollars, with an
estimated carbon storage benefit of between
$66,300 and $88,400 and annual air pollution
benefits between $100,000 and $131,300.

Current Street Tree Management
The Streets/Parks/Facilities division of the
Public Works Department manages the street
trees in the City’s right-of-ways. Staff from this
division proactively manage street trees through
a contract with WCA to prune every street tree
biannually (every other year). This service is
referred to as “grid pruning.” Issues with data
from WCA is outline in a separate report.

City staff also manage street trees reactively,
for example when citizens report fallen branches
to the City through the i-WorQ system. In such
instances, if the debris load is relatively small,
City staff will perform the branch clean-up
using internal staff equipment. If the debris
load is larger, staff will utilize WCA as an on-call
contractor for clean-up.

In cases where city staff are unsure of the
best course of action for a potentially high-risk
tree, WCA is asked to function as a consultant
and provide a recommended course of action.

Management actions such as tree planting and
pest management have not been undertaken
over the last decade or longer. The total number
of staff in the Streets/ Parks/ Facilities division
has dropped by approximately 50 percent over
the last decade.

As of 2022, the City currently invests
approximately $254,000 annually on tree-related
expenses. Of this annual investment total, the
tree trimming contract services are $176,105,
the City maintenance staff time is $60,000, and
additional arborist services are $18,000. Budget
data is shown in Table 14.

Table 10 Tree Canopy Annual Benefits (iTree)
Benefit Annual
Amount
Annual
Value
Pollution Removal 1.865 tons $18,500.

Carbon
Sequestration

80.07 tons $13,700.

Avoided
Stormwater Runoff
46,380 cubic
feet
$3,100/
year
Table 11 Tree Canopy Annual Benefits (GIS)
Benefit Annual
Amount
Annual
Value
Pollution Removal 1.4 tons $13,900.

Carbon
Sequestration
60 tons $10,300.

Avoided
Stormwater Runoff
34,850 cubic
feet
$2,325/
year
Table 14 Signal Hill Current Street Tree Budget
Tree Trimming Contract Services $176,105
City Maintenance Staff Time $60,000
Additional Arborist Services $18,000
Total $254,000
Table 13 Canopy Statistics via GIS Data
Canopy Cover 14%
Overall Stored Carbon Value $1.31 million
Annual Carbon Storage Benefits $66,300
Annual Air Pollution Benefits $100,000
Table 12 Canopy Statistics via iTree
Canopy Cover 21%
Overall Stored Carbon Value $1.75 million
Annual Carbon Storage Benefits $88,400
Annual Air Pollution Benefits $131,300
38 SIGNAL HILL STREET TREE MASTER PLAN
High-Performance Trees

1.4g City Staff Perspectives
Regarding existing trees, city staff reported
the genera/species in Table 15 as performing
well. Generally, city staff hope to see the new
street tree planting palette focus on trees that
have a small to medium mature stature, are
drought-tolerant, and grow relatively slowly.

They also would like to see regionally-native
trees planted when possible and appropriate.

Staff specifically requested the species listed
in Table 16 to be included in the planting
palette. All staff-recommended species other
than sweetshade (due to qualities such as
weak branch strength and medium water use)
were incorporated into the new palette.

Staff reported the trees in Table 17 to be
problematic, for reasons including utility
conflict, sidewalk heaving, and limb drop. These
species were not included on the new palette.

Table 15 Species Performing Well
Common Name Botanical Name
Australian willow Geijera parviflora
Goldenrain tree Koelreuteria paniculata
Crape myrtle Lagerstroemia indica
Geijera parviflora, Australian Willow
Koelreuteria paniculata, Goldenrain Tree
Photo: G. Castriotta
Lagerstroemia indica, Crape Myrtle
SECTION 1: BACKGROUND 39
Trees the Staff Would Like To See on the Palette
Table 16 Species to Consider for New
Planting Palette
Common Name Botanical Name
Sweetshade Hymenosporum flavum
Desert willow Chilopsis linearis
Palo blanco Acacia willardiana
Tecate cypress Hesperocyparis forbesii
Hymenosporum flavum, Sweetshade Chilopsis linearis, Desert Willow Photo: G. Applegate
Acacia willardiana, Palo Blanco Hesperocyparis forbesii, Tecate Cypress 40 SIGNAL HILL STREET TREE MASTER PLAN
Problem street trees . . .

Table 17 Most Problematic Species
Common
Name
Botanical
Name
Conditions of
Concern
Gum trees Corymbia &
Eucalyptus
Limb drop in wind
events
Figs Ficus spp. Sidewalk heaving
Sweetgum Liquidambar
styraciflua
Sidewalk heaving,
water line conflicts
Magnolia Magnolia
spp.

Limb drop in wind
events, sidewalk
heaving
Chinese elm Ulmus
parvifolia
Limb drop, sidewalk
heaving, power line
conflicts, water
line conflicts
Magnolia grandiflora, Southern Magnolia
Corymbia citriodora, Lemon-Scented Gum Magnolia grandiflora, Southern Magnolia Liquidambar styraciflua, American Sweetgum Ulmus parvifolia,Chinese Elm Photo: J. Klemic
SECTION 1: BACKGROUND 41
. . . and the problems they cause
Dropped limbs
Sidewalk heaving
Waterline conflicts
Powerline conflicts
Photo: A. Kacher
Photo: J. Klemic
Photo: G. Castriotta
Photo: G. Castriotta

2.0 DESIGN & MANAGEMENT PLAN
SECTION 2: DESIGN & MANAGEMENT PLAN 43
This chapter will set some basic goals for the
City of Signal Hill in improving and maintaining
its street tree population. Guiding Goals and
Objectives contains important information
to help frame these goals, as well as specific
ways of achieving them. Planting Design
and Guidelines will include information for
the city to consider to improve street tree
infrastructure, and useful information to
consult when designing a new planting. Design
for the Future discusses possible future urban
forestry endeavors for Signal Hill. Species
Selection Criteria provides a method for
selecting a tree for a site. The Street Tree
Palette includes a basic list and a detailed
palette with photographs, as well information
on how the palette was created.

1. Fill the vacant tree sites.

By far the most important goal of this plan
is fill the existing 1,019 sites in need of live
trees. If the city is able to accomplish this
goal, the total street tree canopy will increase
by roughly 1%. It is also important for the city
to continue to fill sites as trees die or need
removal if the total canopy is to grow. There
are several organizations dedicated to helping
communities plant trees. Below are some
options Signal Hill should pursue to help them
reach their tree planting goals.
1a. Increase the city’s tree canopy by 1% in so doing.

Simply by filling the vacant tree sites, Signal Hill
can actually increase the city's tree canopy by
1%. The tree canopy encompasses all trees in
the city, including those in parks and on private
property. The table below demonstrates the
approximate size and number of trees needed
to accomplish this goal.

Given the limitations of most vacant tree sites,
Example 3 may not be realistic for the city to
achieve, but it demonstrates how effective
larger trees are in providing canopy and
associated shade/heat-reduction benefits.

Example 1 is possible but does not provide

2.1 Guiding Goals &
Objectives
Goals

1. Fill the vacant tree sites.
a. Increase the city’s tree canopy by 1% in so doing.
b. Continue to replace trees in a timely manner as
needed.
c. Tree-planting initiatives can help Signal Hill
achieve this goal.

2. Ensure the long-term health and prosperity of
the city’s street tree canopy by planting the
right tree in the right place.
i. Improve shade equity in the city by focusing on
planting in areas of greater need.
j. Use species well-adapted to local environmental
conditions and design objectives.
k. Provide native animal habitat and well-adapted
trees by planting native species.
l. Achieve a diverse and resilient forest by
following the 10-20-30 rule of community
forestry.

3. Establish a high standard of maintenance and
a sustainable care regimen for the city’s street
trees.

4. Promote public awareness of and involvement in
community forestry care and benefits.
a. Promote the community forestry program’s
progress & achievements.
b. Encourage collaboration between city
departments, local community organizations,
and public schools.
c. Encourage monetary and other contributions
to the community forestry program.
d. Participate in programs that support and
promote the benefits of the community forest.

Table 18 Number of Trees Needed to
Increase Total Tree Canopy by 1%
Example 1: Small/Medium Trees Quantity
Half small-growing trees 600
Half medium-growing trees 600
Total 1200
Example 2: Mixed Sizes Quantity
One-third small-growing trees 269
One-third medium-growing trees 269
One-third large-growing trees 269
Total 807
Example 3: Large Trees Quantity
All large-growing trees 488
Total 488
44 SIGNAL HILL STREET TREE MASTER PLAN
CAL FIRE Urban and Community Forestry
Program Grants
CalFire offers urban forestry grants in
three different sub-categories: Education
and Workforce Development, Urban Forest
Expansion and Improvement, and Urban
Forest Management Activities. For Signal Hill's
immediate priority of planting street trees, the
second category offers the best source of aid.

However, the public works department could
also benefit from the first category, which
could help train staff to care for trees. Should
the city wish to update its tree database or
analyze its tree canopy, the third category
would be helpful. While 2023 grant application
information is not available yet, more
information can be found on CAL FIRE's website,
www.fire.ca.gov. More details can be found on
p. 125.

Tree People
This organization works within the Los Angeles
area to organize tree planting initiatives and
volunteering. It offers training and focuses on
environmental justice. Tree People could prove
an excellent resource for overcoming shade
inequity within the city of Signal Hill. Their
website, www.treepeople.org, provides a wealth
of information and resources regarding trees,
soil, water, and plants.

This plan strongly recommends reaching out to
both CAL FIRE and Tree People for funding and
other resources in replenishing the street tree
canopy, as well as future urban forestry goals.

2. Ensure the long-term health and
prosperity of the city’s street tree canopy
by planting the right tree in the right place.

Signal Hill does not merely need to fill the
vacant sites; it must fill those sites with the
trees that are best suited to them, which will
ensure that the tree lives a long and healthy
life, without premature removal. There are
many factors to consider when planting a tree
in a site.

First, a tree's eventual full size must be
considered. Many trees in Signal Hill have been
as many benefits without any larger trees.

Therefore, a version of Example 2 might prove
the best method of expanding Signal Hill's tree
canopy by filling vacant street tree sites.
1b. Continue to replace trees in a timely
manner as needed.

While filling the currently empty sites is the first
priority, the city must continue to monitor its
street tree population and quickly fill any new
vacancies if it is to continue to grow its tree
canopy. The following resources can aid in this
endeavor. Additionally, when filling any tree
sites, the city should analyze whether the site
can accommodate a healthy tree, if the site
can be modified to do so, or if another, more
appropriate site should be created in its place.
1c. Tree-planting initiatives can help Signal Hill
achieve this goal.

There are many resources available to help
communities seeking to improve their tree
canopies. The two mentioned below can
provide immediate assistance in planting trees
as well as other resources. Additional programs
can help sustain the canopy down the road
and ensure the community is aware of the
importance of its street trees. Those programs
will be discussed in a later section.

SECTION 2: DESIGN & MANAGEMENT PLAN 45
Figure 2.1.1: The Right Tree in the Right Place
lopped off to avoid growing into power lines,
for example. In the future, care must be taken
to plant only power line-friendly (i.e. smallgrowing) trees under utility lines. The palette in the following section specifies which trees
are small-growing and thus recommended for
this purpose. However, an area with plenty
of canopy space and a need for shade would
benefit from a medium or large tree if possible.

Trees require a planting area of particular
dimensions based on their size and growing
habits; these parameters are listed in the
palette. Finally, size should also be considered
if a view is to be protected, to ensure that a
tree won't eventually grow to block the desired
vista.

The water needs of a tree are also a crucial
consideration. Given the lack of irrigation
available to many of Signal Hill's street trees,
as well as the current drought conditions, no
species with high water needs were included
in the palette. Some trees do have moderate
water needs, and they must be planted where
they will have access to water in order to
thrive. Many are drought-tolerant but will still
need water to establish.

Additionally, some trees have roots that
aggressively seek out water and can damage
sewer and water lines and even crack sidewalks
or paving. No trees with high root damage
potential were placed on the palette, but some
have moderate potential. These trees can and
should still be used as long as they are not too
close to water and sewer lines, or if there is a
barrier to protect the lines from the roots.

Other considerations include form (is there
room for a full, round tree or would a narrower
tree fit the space better?), foliage (evergreen
or deciduous, densely foliated for shade or
allowing more light through?), blossoms and
fruit (will the tree have litter to clean up?), and
aesthetics. Different tree forms have different
visual functions; some trees have spectacular
blossoms or beautiful fall foliage; people d to
respond strongly to such qualities.

Beyond the physical requirements of trees,
other important elements affect the placement
• Height
• Width
• Shape
• Foliage density
• Growth Rate
• Longevity
• Pollen
• Dropped fruit or
flowers
• Toxicity
• Root damage
• Water needs
• Soil type
• Light preference
• Proximity to buildings,
cars, or pipes
• View
The Right Tree in the Right Place Considerations
46 SIGNAL HILL STREET TREE MASTER PLAN
socio-economic issues. Tree planting efforts
should be focused on areas with greater
socio-economic and environmental difficulties.

GIS data, such as shown in the earlier pages
through CalEnviroScreen, Tree People, USFS,
and Tree Equity Score, as well as from the
Healthy Places Index and the Trust for Public
Land, can all be used to help determine the
areas of greatest need within the city.
2b. Use species well-adapted to local
environmental conditions and design objectives.

Great care has been taken in selecting trees
for the palette that are well-adapted to Signal
Hill's environment and to the changing climate.

Not only are there no trees with high water use
on the palette, several of the species come
from a list of Climate Ready Trees developed
by scientists at UC Davis. The Climate Ready
Tree study evaluates "the ability of promising
but underused species to tolerate stressors of
future climates."1 Species were evaluated for
habitat suitability, physiology, and biological
interactions in their respective climate zones.2
Factors include the ability to withstand heat
and drought, pest resistance, and adaptability.

Once trees were rated, the best scoring
ones were planted in test sites, both parks
and control sites, and their conditions were
monitored. The study began in 2016 and is
ongoing. Southern California was divided into
Coastal and Inland; given Signal Hill's proximity
to the ocean, trees from the Coastal list were
selected for the city's street tree palette. Not
all trees on this list thrived, as indicated by
the above table. Some of the more droughttolerant species, like Tecate Cypress, might have been overwatered in coastal parks or
intolerant of salt spray. They may work still well
for Signal Hill and are certainly worth trying.
1 https://climatereadytrees.ucdavis.edu/
2 http://climatereadytrees.ucdavis.edu/why-climate-ready-trees/ of trees within the city and the selection of
appropriate species.
2a. Improve shade equity in the city by
focusing on planting in areas of greater need.

For Signal Hill, one of the most important
factors for tree placement is environmental
justice. Some parts of the city, such as Zone
4, fare consistently better then others in
terms of shade, heat islands, pollution, and
Survival Rates (%) for Climate Ready Trees in the Southern California Coastal and Inland Climate Zones Park Sites Reference Sites All Sites
Coast Inland All Coast Inland All Coast Inland All
Acacia aneura a (Mulga) 100 88 94 100 100 100 100 92 96 Cedrela fissilis b (Brazilian Cedarwood) 63 100 75 75
Celtis reticulata a (Netleaf Hackberry) 100 100 100 100 100 100 100 Chilopsis linearis ‘Bubba’ c (Desert Willow) 88 100 92 92 Corymbia papuana a
(Ghost Gum) 63 100 75 100 67 100 83
Dalbergia sissoo a (Rosewood) 75 100 100 100 83 100 92
Hesperocyparis forbesii a (Tecate Cypress) 38 75 56 50 75 63 42 75 78 Mariosousa willardiana a (Palo Blanco) 63 100 81 75 100 88 67 100 83 Parkinsonia x ‘Desert Museum’ c (Palo Verde) 100 100 100 100 100 100 Pistacia ‘Red Push’ a (Red Push Pistache) 75 100 88 100 100 100 83 100 92 Prososis glandulosa x Maverick a (Mesquite) 100 100 100 100 100 100 100 100 100 Prunus ilicifola spp. Lyonii b (Catalina Cherry) 88 88 100 100 92 92 Quercus fusiformis a (Escarpment Live Oak) 88 38 63 100 100 100 92 58 75 Quercus tomentella
Average
a (Island Oak) 88 88 88 100 100 100 92 92 92
78 90 84 92 98 95 83 92 88
a. Both Coastal And Inland Sites b. Coastal Sites Only c. Inland Sites Only Figure 2.1.2: Survival Rates for Climate Ready Trees. Source: McPherson et. al., "Climate-ready tree study: update for Southern California communities" in Western Arborist, 2020. https://www.srs.fs.usda.gov/pubs/60414 SECTION 2: DESIGN & MANAGEMENT PLAN 47
2c. Provide native animal habitat and welladapted trees by planting native species.

Trees and plants native to Southern California
are more likely to be adapted to conditions
here. Several of the trees on the Climate
Ready Tree list are native, but there are plenty
more to choose from. Native plants have
evolved over time to thrive in local conditions
with various adaptations. Some plants have
developed deeper or wider root systems to
seek out water where other plants cannot
reach. Some go summer dormant, conserving
resources when water is scarce and springing
back to life in winter or spring, after California's
seasonal rains. As a result, they have gained a
reputation for being ugly or "wild"-looking, but
native plants in a garden can be cared for and
trimmed to look well-groomed all year.

Many natives have adapted to the particular
soils found here, and even the insects
and microbes. These adaptations make
them more likely to survive local pests and
diseases, unless the pest is invasive. Some
form symbiotic relationships with the fungi
found in soil, also better enabling them to
survive drought conditions. Because of these
adaptations, native plants often require
less management, such as fertilizer or soil
amendments, than non-natives. Some native
plants actually don't tolerate summer irrigation,
as they are genetically prepared for dry
summers.

Native plants and trees can also be quite
beautiful. Some, like the Western Redbud
or Ceanothus, both included in the palette,
produce gorgeous, brilliantly colored flowers
in spring. These flowers attract pollinators like
bees, butterflies, and hummingbirds. Santa
Cruz Ironwood has beautifully shaped leaves,
cream flowers in spring, and provides great
shade. The Catalina Cherry is a "triple threat":
a California native plant found on the Climate
Ready Tree list with very low water needs. It
also produces cream flowers in spring, and
small cherries in summer, helping to support
native wildlife. All of these reasons make it
important to prioritize planting more native
trees in Signal Hill, and many are included in the
palette.

Many native plants have roots that spread
farther or dig deeper as an adaptation to
seasonal drought, helping to reduce soil
erosion and improve water quality.

Native plants provide habitat for a
wide range of native animal species,
supporting greater biodiversity than
introduced species.

Native plants are adapted
to the local climate,
pests, diseases, and soil.

Erosion Control & Water Quality Habitat For Wildlife Resilience Benefits of Native Plants
Figure 2.1.3: Benefits of Native Plants
48 SIGNAL HILL STREET TREE MASTER PLAN

3. Establish a high standard of maintenance
and a sustainable care regimen for the city’s
street trees.

Planting new trees will prove a costly endeavor
if proper care is not provided to those trees
to ensure their successful establishment and
long-term health. And of course, the existing
tree canopy needs attention, as well. The
city must therefore plan carefully to invest in
the health of its street trees by developing a
realistic and sustainable maintenance regime
and adhering to it. Chapters 3 and 4 provide
more detailed recommendations regarding
street tree care and maintenance.

4. Promote public awareness of and
community forest benefits and involvement
in tree care.

The public can play a large role in maintaining
the Community Forest, including street trees.

Tree planting volunteer events can both reduce
the cost of planting new trees and create a
sense of ownership and investment from the
community. There are many ways to foster
public investment, detailed in the following
pages. Most importantly, the public should be
made aware of the importance of the street
tree canopy and all the benefits it provides
them.
2d. Achieve a diverse and resilient forest by
following the 10-20-30 rule of community
forestry.

A healthy urban forest needs species diversity.

A good rule of thumb is that a forest should
contain no more than 10% of any one species,
20% of any one genus, and 30% of any one
family. Too many trees of a single family, genus,
or species leaves the population vulnerable
to pests and diseases. As mentioned in the
previous chapter, Chinese elms comprise 15%
of the current street tree population, and
Mexican fan palms comprise 10%. For this and
other reasons, these species are not included
in the new palette.

Signal Hill's street trees do comply with the
genus and family allotment. Nevertheless, the
updated palette includes many trees that were
never on previous palettes are not present in
the street tree population. The new palette is
also considerably more diverse than the 2010
palette. As a result, the street tree population
should further diversify as new trees are
planted, for the benefit of the entire canopy.

The 10-20-30
Rule of Urban Forestry
A healthy urban forest contains no more than:

Kingdom
Phylum
Class
Order
Family
Genus
Species
30% of any 1 family
20% of any 1 genus
10% of any 1 species
Figure 2.1.4: The 10-20-30 Rule of Urban Forestry
SECTION 2: DESIGN & MANAGEMENT PLAN 49
The Benefits of Trees
Trees provide shade and reduce heat.

Trees are integral to fighting the effects of urban
heat islands. In urban areas, shaded surfaces may
be 20-45 degrees cooler and evapotranspiration
can reduce peak summer temperatures by 2-9
degrees. Trees help drive economic development.

Recent studies have revealed that people will travel
farther, pay more for goods and services, and visit
commercial districts more frequently when trees and
landscaping are present.

Trees moderate wind.

When trees are planted strategically,
they not only reduce wind exposure
but can reduce heating bills in the
winter by 2 to 8 percent.

Trees increase property values.

The beauty of a well-planted property and
its surrounding street and neighborhood
can raise residential property value by as
much as 20 percent.

Trees provide habitat for
animals, increasing biodiversity.

Supporting a variety of insects, birds, and
mammals with food and shelter, trees are a
city’s prime medium for attracting wildlife.

Trees help create a sense of place.

To come home to a green and shaded
community transforms a location into a
beautiful place.

Trees have a positive impact on
people’s physical & mental health.

Spending time around trees and looking at trees
reduces stress, lowers blood pressure and improves
mood. Trees improve water quality.

Leaves slow the impact of drops to
reduce erosion and surface runoff, while
roots help filter stormwater to improve
groundwater quality and quantity.

Trees provide energy savings.

The cooling, sheltering effect of trees
helps lower energy use and bills.

Trees improve air quality
and reduce pollution.

By producing oxygen and filtering
airborne particulates, trees help
reduce air pollution.

Figure 2.1.5: The Benefits of Trees
50 SIGNAL HILL STREET TREE MASTER PLAN
involvement. This type of engagement is only
possible if the city works hard to promote the
new Street Tree Master Plan.
4d. Participate in programs that support
and promote the benefits of the community
forest.

One way for the city to involve the public
is to participate in national initiatives that
share similar goals. These initiatives offer
resources and support that can assist the city
with its community forestry efforts. Formal
participation in such programs communicates
to the public the goals, values, and approaches
that are shared by the initiative and the city
community forestry program. Participation also
promotes broader understanding of community
forestry issues and benefits. In addition to
aid from CAL FIRE and Tree People, the city
can apply for programs such as Tree City USA
through the Arbor Day Foundation, and Bee
City USA. National initiatives such as these can
really help to garner the attention and support
of the public.

Tree City USA
“Tree City USA” is an Arbor Day Foundation
program that works to establish, promote, and
celebrate urban tree canopies. In partnership
with the USDA Forest Service, Urban and
Community Forestry, and the National
Association of State Foresters, the status of
Tree City USA is awarded to cities who meet
the foundation’s standards of urban forestry
management.

In order to achieve Tree City USA status, a
community must meet four standards of sound
urban forestry management:
• A tree board or department
• A tree ordinance
• A community forestry program with an
annual budget of at least $2 per capita
• Celebrate Arbor Day
The Tree City USA program provides the
city’s community forestry program direction,
technical assistance, public attention, and
national recognition; and would place Signal
Hill within a network of over 3,400 recognized
communities.

Bee City USA
Bee City USA is a program, launched in 2012,
that invites cities to make commitments for
providing sustainable habitats for pollinators.

According to the program’s website, “85% of
flowering plants and trees rely on pollinators for
the survival of their species. …Entire species
[of native bees and other pollinators] are
disappearing at alarming rates as they battle
most of the same enemies as honey bees –
loss of habitat essential for food and shelter,
4a. Promote the community forestry
program’s progress & achievements.

For Signal Hill, promoting the new Street
Tree Master Plan is critical to achieving the
plan's goals. Citizens need to be engaged and
supportive to help acquire funding and move
the project forward.
4b. Encourage collaboration between city
departments, local community organizations,
and public schools.

Communication between different civic
organizations can help promote planting
initiatives, updates to policy, and the
value of street trees. Schools can be
instrumental in developing such programs,
and community groups can boost a project.

These organizations can also help support tree
improvements economically. City departments
must work together to promote the Street
Tree Master Plan if it is to be successful and
appreciated by residents.
4c. Encourage monetary and other
contributions to the community forestry
program.

Encouraging citizens to invest in the health
and beauty of their city through tree planting
will greatly increase the city's ability to fund
tree planting initiatives and maintain the city's
street trees. Residents can feel proud of their
SECTION 2: DESIGN & MANAGEMENT PLAN 51
inappropriate pesticide use, diseases, and
parasites.”
The Bee City USA program is intended to raise
awareness of these issues and encourage
communities to take actions that will support
populations of pollinators. Some of the
guidelines for pollinator-friendly habitat
include:
• Provide diverse and abundant pollinator
food sources (nectar and pollen from
blooming plants) that bloom in succession.
• Provide water for drinking, nest-building
and cooling, diluting stored honey, and
butterfly “puddling”.
• Avoid the use of pesticides, or carry out
the use of pesticide to impart the least ill
effects on pollinators.
• Comprise plantings of mostly, if not all,
native species of grasses, perennials,
shrubs, and trees. (Many native pollinators
prefer or depend on the native plants with
which they have co-evolved for millions of
years.)
• Source plants from nurseries that do not
treat seeds with neonicotinoid pesticides,
which permeate the entire plant and can
remain active for years. (Some plants may
be labeled “bee-friendly” even though
they were grown from seeds treated with
“neonics”.)
• Provide for safe and humane removal of
bees when required.
• Provide undisturbed spaces (leaf piles,
unmowed fields, fallen trees) for nesting
and overwintering for native pollinators.

Collectively, the city and private land owners
can follow these guidelines to plant and
manage landscapes in a manner that will
support sustainable habitats for pollinators.

Ultimately, if the Signal Hill wishes to fill its
vacant tree sites and properly maintain a
healthy street tree canopy in the long term,
all city departments must work together with
residents. Trees are vitally important to a
clean, beautiful, and comfortable Signal Hill; as
long as this fact is understood by the public,
support should be easily attained.
52 SIGNAL HILL STREET TREE MASTER PLAN
Major Streets Plantings
Same process as above for major streets
within new developments. For existing streets,
the City initiates the plans, either developing
them in-house or hiring a consulting landscape
architect. The plans are presented to the public
for comment and approved by City Council as
a capital improvement budget item. Any new
construction or renovation projects should
include new street tree sites with irrigation
installed.

Residential Neighborhood Plantings.

The Public Works Director or designee selects
species and placement in conformance with
Master Plan criteria and with prior notification
of fronting property owners. Residents can
choose from the appropriate species for the
site provided by the director.

This section provides design guidance to be
consulted during development of planting
designs within public rights-of-way. It begins
with an overview of the different planting
processes depending on the type of project.

Most importantly, Signal Hill needs to begin
filling its vacant street sites. As the city begins
this task, these guidelines can be used to
determine how different street tree plantings
can affect the aesthetic of a location based on
whether the site is located on a major street
or in a residential neighborhood. These
guidelines may vary from current policy, but
are recommended for any future development
of the city. Certain areas may have specific
design requirements; check with the Planning
Commission to confirm.

New Developments
After consulting regulatory documents and
city staff, the developer’s landscape architect
submits plans for City review. The City reviews
the plans for conformance with current
regulations, works with the developer to adjust
the plans, and may present to the Planning
Commission or City Council as part of the
permit approval process. New developments
should be required to plant new street trees
using the included guidelines, and should also
be required to install irrigation for those new
street trees.

2.2b Principles of Community Forest
Design
Landscape design is the process of altering
the environment to meet human needs. The
changes can be very subtle or quite dramatic.

When sensitively carried out, the environment
is enhanced, not harmed by such changes. A
careful design considers the needs of species
other than humans, and reveals hidden natural
wonders. Good landscape design finds the
balance between human needs and the rest
of the natural world. In addition to working well
with the natural and developed environments,
trees and plants should be chosen and sited to
make the highest contribution to the character
of the neighborhood or commercial area in
which it is planted.

In the case of the community forest, the
human needs can vary greatly, as can the
environmental conditions. What are the
conditions of the site that will affect the
plantings there? Will cars or trucks be driving
under its limbs? Is the tree being planted
to reduce the effects of wind, or in an area
prone to high winds that can cause limb loss
in some species? Or maybe the site's sunny,
open location allows for a larger tree that will
provide the city exponentially more shade than
a smaller species. These are just some of the
issues to consider when trying to choose a tree

2.2 Planting Design
Guidelines
SECTION 2: DESIGN & MANAGEMENT PLAN 53
that will meet the needs of the people who use
the site.

Trees can also be used to solve a variety of
problems. Shade trees on the south and west
sides of a building can significantly reduce
cooling costs, or even provide heat relief for
someone waiting for the bus. Trees can catch
the particulates emitted by cars and reduce
pollution of air in adjacent backyards and along
sidewalks. Trees can help control erosion and
aid in stormwater control on slopes. After all
these needs and potential uses have been
considered, the aesthetic character of the
tree must be evaluated. Aesthetics is not an
entirely subjective matter. Trees have a number
of visual characteristics - such as scale,
form, color and texture - that help determine
appropriate species selection.

2.2c Universal Planting Design Guidelines
The following guidelines have been formulated
to direct the design of the community forest
as a whole. They have been organized into
the following three categories: Enhancing
Character & Aesthetics, Increasing Forest
Resiliency, and Supporting Maintenance &
Safety. Guidelines specific to the major streets
and neighborhoods appear in the next sections.

It should be noted that the design guidelines
can be applied to the renovation of existing
areas as well as new construction. Where
existing landscaping has been found to
conflict with the use of an area or create high
maintenance conditions, these guidelines
can aid in planning the renovation of those
areas, thereby creating a more effective
relationship between use and design as well
as a corresponding reduction in maintenance
problems.

Enhancing Character & Aesthetics

1. Respect and Emphasize the City’s
Geographic Setting.
• Frame views from the public right-of-way
to Signal Hill, as well as views of neighboring
mountains, ocean, and ports.
• Consider accent species in the foreground
of such views.
• Screen objectionable views, including large
parking lots or oil derricks, with appropriate
plantings.

2. Complement existing trees and other
vegetation.
• New tree forms, colors, and textures should
be compatible.
• Horticultural requirements should be
consistent for healthy growth.
• Use special care when modifying conditions
near existing natives.

3. Use trees to create a variety of spatial
experiences.
• Where appropriate, use trees to enclose
space with allees, bosques, or groves.
• To emphasize openness, use a single large
specimen tree as a focal point within a
large open space.

Round
Spreading
Pyramidal Oval Conical
Vase
Columnar
Open Weeping Irregular
Tree
Forms
Figure 2.2.1: Tree Forms
54 SIGNAL HILL STREET TREE MASTER PLAN
Increasing Forest Resiliency

1. Use native species where appropriate.

2. Plant to attract and support wildlife.
• Select species that offer food, housing, and
water, especially for indigenous fauna. Experts
on local wildlife species can recommend
appropriate species to meet these needs.
• Develop plantings that bloom in succession,
providing pollinator food sources throughout
the seasons.
• Plant wildlife-attracting species in sizable
numbers and with some continuity throughout
the community to mimic natural habitat;
isolated patches are less effective.
• Incorporate native species of grasses,
perennials, shrubs, and trees to the greatest
extent practical.

3. Select trees and plantings adapted to the
environmental conditions of the site. Refer to
the Species Selection Criteria in the following
section for more information.

4. Satisfy any functional reasons for the
planting.
• Water conservation and quality
• Energy conservation
• Wind reduction
• Air pollution abatement
• Noise reduction
• Shading pavement to reduce heat island
effect
• Screening objectionable views

5. Integrate low impact development best
management practices for stormwater within
public right-of-way plantings, where practical.

Potential applications include tree wells,
medians, parkway strips, and meandering
sidewalks.

6. Diversify types and species where possible
to avoid monotonous landscapes and
overplanting of popular species.
• At least two species should be utilized on each
block to ensure diversity.
• lntermix accent species in the dominant tree
grid, as understory species, or to highlight key
buildings or intersections.

Supporting Maintenance & Safety

1. Plant to provide the intended performance and
aesthetic with the lowest water usage.
• Species with low to very low water use ratings
are preferred.
• Group species by similar water needs in
hydrozones.
• Minimize the number of hydrozones/irrigation
valves per planting area.
• Trees and understory plantings should have
compatible water needs.

Universal Planting Design Guidelines
Enhancing Character & Aesthetics

1. Respect and emphasize the city’s geographic
setting.

2. Complement existing trees and other vegetation.

3. Use trees to create a variety of spatial
experiences.

Increasing Forest Resiliency

1. Use native species where appropriate.

2. Plant to attract and support wildlife.

3. Select trees and plantings adapted to the
environmental conditions of the site.

4. Satisfy any functional reasons for the planting.

5. Integrate low impact development best
management practices for stormwater within
public right-of-way plantings, where practical.

6. Diversify types and species where possible.

Supporting Maintenance & Safety

1. Plant to provide the intended performance and
aesthetic with the lowest water usage.

2. Ensure planting designs conform to current local
and state regulations.

3. Consider the non-optimum conditions of street
tree plantings when designing tree spacing.

4. Design tree spacing based on mature plant sizes.

5. Place trees away from conflicting uses.

6. Locate trees to minimize conflict with overhead
utilities.

7. Locate trees to minimize conflict with
underground utilities.

8. Provide planting spaces that accommodate
healthy tree growth.

SECTION 2: DESIGN & MANAGEMENT PLAN 55

2. Ensure planting designs conform to current local
and state regulations.
• Do not obstruct sightlines at intersections or
traffic signage.
• Comply with water allowance and irrigation
requirements.
• Refer to Chapter 4, Findings & Updates, for
local policies. Contact the City Planning to
determine if other regulations apply to your
project.

3. Consider the non-optimum conditions of street
tree plantings when designing tree spacing. The
following rule of thumb applies to street trees
which are to be planted in an even-spacing
pattern:

Broad trees: 30 to 40 feet apart
Average trees: 20 to 30 feet apart
Narrow trees: 15 to 20 feet apart
• Design tree spacing based on mature plant sizes.

4. Place trees away from conflicting uses:
• Intersections. Minimum 15 feet from curb return
at intersections for sidewalk and median trees to
keep traffic sightlines clear.
• Traffic and monument signs. Placed far enough
away to allow easy visibility, given the speed of
traffic on the street.
• Parking. For parallel parking, place trees
between stall markings to avoid damage
from opening car doors.

Figure 2.2.2: Tree Planting Regulations. Recommended spacing requirements for new street trees. 56 SIGNAL HILL STREET TREE MASTER PLAN
• Driveways. No closer than 10 feet from any
driveway.
• Pedestrian and wheelchair clearances.

A minimum of 4 feet of clear sidewalk
should be provided to allow comfortable
passage.
• Street lights. Minimum 20 feet from light
standards to prevent light obstruction.
• Utility poles. At least 10 feet so as not to
obstruct access to the poles.
• Fire hydrants. At least 10 feet away to keep
accessible.
• Meter and valve boxes. Far enough to keep
clear of tree wells. At least 5 feet away.
• Other street furniture - benches, trash
cans, etc. Space in a pleasing, logical and
functional composition. Often aligned with
trees in a sidewalk amenity zone along the
curb. At least 5 feet away.

5. Locate trees to minimize conflict with
overhead utilities.
• Where possible, utilities should be located
underground; or, if overhead, aligned to
accommodate street tree planting.
• Where overhead utilities exist, plant small
trees (refer to Planting Palette) that will not
reach the height of the wires.

6. Locate trees to minimize conflict with
underground utilities.
• Plant trees as far away as possible from
utilities, to avoid damage by roots, and to
avoid trenching through the root zone when
lines are serviced.
• Contact utility companies to locate lines
before determining planting location.

7. Provide planting spaces that accommodate
healthy tree growth.
• Refer to the planting palette to match
planting design to the available planting
space size.
• Where possible, enlarge the existing
planting areas.
• Under new paving where available space
confines planting areas, provide structural
soils or cells to increase rooting space.
• To maximize growth and health of trees,
provide a minimum of 1,000 cubic feet of
loam soil per tree, or aim for the preferred

1.5 to 2 cubic feet of loam soil per square
foot of mature tree canopy area.
• Tree Wells. At a minimum, should be
4 x 6 x 3 ft. deep, with 6 x 6 or larger
recommended. Tree wells with an opening
of less than 8.3-square-feet (2.5 x 2.5)
will support only small trees to maturity or
medium-sized species for 10 to 15 years.

Tree wells with an opening of 48-squarefeet (6 x 8), on the other hand, will support large trees to maturity. Narrow parkways
can be utilized by allowing the lateral
spread of tree roots (e.g. 2.5 x 8 ft instead
of 2.5 by 4 ft dimension for the tree well).

Use of root barriers on two sides will help
prevent root damage and allow for a wider
variety of species.
• Parkway Strips. The design of new streets or
retrofitting of existing streets with a 6-ft.-
wide parkway is essential for healthy tree
growth. A 2.5-feet-wide planting strip will
not support a medium or large sized tree
without pavement damage; the minimum
recommended width is 4 feet. The benefit
of planter strips over tree wells is increased
tree vigor, due to the larger surface area of
exposed soil.
• Where possible, provide for 7-8' sidewalks,
allowing for 3-4' wide planting cutouts.
• Where possible, install modular suspended
pavement systems (see "Modular
Suspended Pavement Systems" in Appendix
for details).

Figure 2.2.3: Existing vs. Suggested Street Tree Planting Design (following page). New development in Signal Hill should implement the planting design strategies from
this document.

SECTION 2: DESIGN & MANAGEMENT PLAN 57
Existing
Existing
Suggested
Suggested
58 SIGNAL HILL STREET TREE MASTER PLAN
In the immediate future, Signal Hill's top
priority should be filling its vacant street tree
sites. Beyond that, the city should attempt to
maintain its current street trees to the highest
possible level, and to make sure the public is
aware of the importance of the street tree
canopy. But as these goals are accomplished,
Signal Hill should also be looking to the future.

Phytoremediation
One possible future objective could be to use
street trees to phytoremediate areas of the
public right of way that have contamination
from former oil drilling or other pollution.

Phytoremediation, "the treatment of
pollutants or waste (as in contaminated soil or
groundwater) by the use of green plants that
remove, degrade, or stabilize the undesirable
substances (such as toxic metals),"1 is
more commonly used to treat sites, called
brownfields, that have been contaminated
from former industrial use. However, given
the widespread history of oil production in the
city (see p. 23) and the current oil derricks
well-integrated into public spaces in Signal
Hill, street trees could potentially be used for
this purpose. The city would need to identify
which street trees are situated on old oil sites,
or it could decide to create new street tree
sites on current oil sites once those sites are
decommissioned. Current GIS data suggests
1 https://www.merriam-webster.com/dictionary/phytoremediation that there are plenty of possible locations for
street tree phytoremediation, and this data can
be used to help the city create a list of possible
sites. In fact, some eucalyptus trees could
already be performing this role, removing toxins
from the soil along Willow Street, for example.
all waste from phytoremediation trees must
go to the landfill and not to any composting or
mulching center. Currently, street tree waste
from the city already goes to the landfill, but if
this system were to change, phytoremediation
sites would need to be carefully tracked and
tree litter treated separately to ensure that all
contaminated waste would go to the landfill.

The most commonly used trees for oil field
phytoremediation are poplars and willows.2
These species are not a good fit for Signal Hill's
street tree palette as they are high water use
and also have invasive roots that can damage
underground utilities. Eucalyptus species can
also be used, and have lower water needs,
but present other problems like invasiveness,
flammability, and limb drop. However, because
research on this process is relatively new and
ongoing, there are some other species that
could be possible and might be a better fit for
Signal Hill. Acacia sieberiana proved effective
in Sudan,3 and var. woodii grows well in South
Africa,4 a similar climate to Southern California.

Local research on native plant species has also
been conducted. A future street tree plan might
include these species for phytoremediation as
long as proper care is taken in disposal. Since
research on this topic is ongoing, additional
species may be possible.
2 https://clu-in.org/download/studentpapers/A_Van_Epps-Final.pdf 3 https://doi.org/10.1080/15226514.2022.2083575
4 https://treesa.org/acacia-sieberiana/

2.3 Design for the Future
Once phytoremediation sites are established,
the city must take care to track all locations
carefully. Phytoremediation can work in
different ways depending on which species are
used to remediate which chemicals. Sometimes
plants break down the chemicals, in which
case phytoremediating species can be treated
like any other plant. But others take up the
chemicals into their roots, branches, or leaves;
thus their byproducts, such as leaf litter or
trimmed/downed branches, could be toxic. If
this type of phytoremediation is implemented,
Active Oil & Gas
Plugged Oil & Gas
Idle Oil & Gas
Lemon-Scented Gum
Figure 2.3.1: Possible Existing Phytoremediation in Signal Hill Street Trees. Lemon-scented gum (Eucalyptus citriodora) intermixed with oil sites on Willow St near Cherry Ave.

Willow St
SECTION 2: DESIGN & MANAGEMENT PLAN 59
Further Goals
As Signal Hill gradually refills the vacant tree
sites, strengthens its tree canopy, and moves
toward shade equity within the city, it should
try to incorporate the entire canopy into its
goals. Tying together the Parks plan as well
as property owners' yards into a Community
Forest Plan would allow the city to achieve its
canopy goals with far greater efficiency, and
benefit the entire city.

One way to better involve the community in
tree planting goals would be to provide free
trees to residents, instead of charging them.

Los Angeles' City Plants program provides free
trees for residents' yards, and plants street
trees free of charge upon request. The process
requires application and approval, as well as
a commitment from residents to care for
the trees during establishment, 3-5, years,
ensuring the city's investment. San Francisco,
on the other hand, ensures the health of its
street trees by placing watering responsibility
solely with the city. Both methods are worth
considering.

Together with its canopy goals, the city could
consider adding additional green initiatives
such as a mulching program, where a portion
of mulch from city tree trimmings is reserved
for city use as well as for the public. The Los
Angeles Department of Sanitation provides
such a program. If Signal Hill's mulching needs
increase due to tree planting initiatives, such a
program could save money.

Finally, the city should continue to address
issues of climate justice, especially relating to
tree canopy coverage.5 Information included in
this document can be used to pursue grants
to help counteract this problem, and the city
should act now to counter shade disparity
within its borders. Regardless of future actions,
the city can follow this plan, especially the next
section, to start on the road to a greener, more
equitable city.
5 https://pdxscholar.library.pdx.edu/toward-resilient-futures/5/ Acacia (vachellia) sieberiana var. woodii, or Paperbark Thorn, in South Africa. Photo: G. Ebedes 60 SIGNAL HILL STREET TREE MASTER PLAN

2.4 Species Selection Criteria
The following pages provide a course of action
for the city to take when maintaining and
selecting street trees. The first diagram (Figure

2.4.1) outlines the procedures already in place
for maintaining existing trees. The second
diagram (Figure 2.4.2) provides a method for
selecting a new tree for a vacant site. The
third diagram (Figure 2.4.3) provides a more
comprehensive selection method.

Figure 2.4.2 is intended to provide an overview
of the selection process and trees available in
each size category, using common names. It
gives a snapshot of which trees have stronger
branches for windy locations, and whether
trees have low or moderate root damage
potential. A more versatile tree that could
be planted in, for example, a windy location
with nearby water lines, should obviously
be prioritized for those limited locations.

In the interest of creating a more diverse
urban forest, trees that can only be planted
without restrictions should be prioritized
in sites without limitations on canopy size,
root invasion, or wind; otherwise, the more
versatile trees will come to occupy too large
a percentage of the canopy. To this end,
the chart lists all possible trees that can be
planted at each site; it bolds the species that
are more limited in use. For the same reason,
larger trees should be planted when space is
available, otherwise the street tree canopy
will be comprised entirely of small trees with
more limited shading and pollution reduction
potential.

Figure 2.4.3 gives a complete view of all the
trees available, using Latin names and showing
whether they are flowering, evergreen, or
deciduous. This chart is intended to aid in
selecting a particular tree for a particular site.

Once the available species are determined from
Figure 2.4.2, the detailed selector that follows
in Figure 2.4.3 allows the user to decide which
type of tree would be the best choice. Basic
information on each tree follows in the palette
list on pp. 67-69, and detailed information,
including photographs, can be found in the
palette on pp. 70-81. The trees are listed
alphabetically by Latin name in the palettes.

While this Master Plan does not recommend
planting a single species of tree per block,
should the city wish to provide an area with
a certain character, two species may be
assigned. For example, near the city entrance
sign on Cherry Ave, the current palm trees
could be gradually be replaced by just Incense
Cedars and Santa Cruz Ironwoods. The trees
are low-water native species which are tall and
narrow, similar to palms, but with greater shade
and carbon absorption capacity.

Yes
Yes
Is the site vacant?
Is the existing tree in good health?
Leave it be. Can Public Works solve the issue?
No
No
No
Proceed. Contact arborist.

Figure 2.4.1: Maintenance Protocol for Existing Trees
SECTION 2: DESIGN & MANAGEMENT PLAN 61
Is the site vacant?
Yes
Small Space
(small tree well, near building,
power lines, or utilities)
Medium Space
(not near power line)
Large Space
(unobstructed canopy)
Windy
Location
Normal Wind
Conditions
Windy
Location
Normal Wind
Conditions
Windy
Location
Normal Wind
Conditions
Normal Wind
Conditions
Near underground
utility
Near underground
utility
Ample Root
Space
Ample Root
Space
Blue Palo Verde
Crape Myrtle
Feather Bush
Kolomona
Laurel Sumac
Mulga
Palo Blanco
Ray Hartman Ceanothus
Toyon
Weeping Bottlebrush
Western Redbud
Madrone
Olive Tree
Red Push Pistache
Australian Willow
Chitalpa
Desert Willow
Hollyleaf Cherry
Madrone
Maverick Mesquite
Netleaf Hackberry
Olive Tree
Red Push Pistache
Rose Lantern
Goldenrain Tree
Australian Willow
Brazilian Cedarwood
Brisbane Box
California Laurel
Chitalpa
Desert Willow
Escarpment Live Oak
Hollyleaf Cherry
Madrone
Maverick Mesquite
Netleaf Hackberry
Olive Tree
Red Push Pistache
Rose Lantern
Goldenrain Tree
Santa Cruz Island
Ironwood
Tecate Cypress
Tipu
California Laurel
Excarpment Live Oak
Madrone
Olive Tree
Peppermint Tree
Red Push Pistache
Santa Cruz Island
Ironwood
Tecate Cypress
African Fern Pine
River She-Oak
Coast Live Oak African Fern Pine
Coast Live Oak
Incense Cedar
Indian Rosewood
Island Oak
River She-Oak
Species in bolded type should be given priority in the
associated conditions to ensure species variety in the
street tree canopy. E.g., Brazilian Cedarwood should
be prioritized over Australian Willow in a medium site
with ample root space and normal wind conditions.

Figure 2.4.2: Method of Selecting New Trees for Vacant Sites. 62 SIGNAL HILL STREET TREE MASTER PLAN
Species in bolded type should be given priority in the
associated conditions to ensure species variety in
the street tree canopy. E.g., Prunus ilicifolia should
be given priority over Arbutus 'Marina' when planting
a medium-sized, evergreen, flowering tree in normal
wind conditions near underground utilities.

Pistacia
‘Red Push’
Is the site vacant?
Yes
Small Space
(small tree well, near building,
power lines, or utilities)
Medium Space
(not near power line)
Deciduous Evergreen,
Flowering
Acacia aneura
Callistemon
viminalis
Ceanothus
‘Ray Hartman’
Heteromeles
arbutifolia
Malosma
laurina
Senna
surattensis
Near underground
utilities
Windy
Location
Normal Wind
Conditions
Deciduous Evergreen
Evergreen
Deciduous,
Not Flowering
Pistacia
‘Red Push’
Deciduous,
Not Flowering
Arbutus
‘Marina’
Olea
europea
Chilopsis linearis
Chitalpa tashkentensis
Koelreuteria
paniculata ‘Rose
Lantern’
Prosopis glandulosa
‘Maverick’
Celtis
laevigata var. reticulata
Pistacia ‘Red
Push’
Arbutus
‘Marina’
Prunus
ilicifolia
ssp. lyonii
Geijera
parviflora
Olea
europea
Cercis
occidentalis
Lagerstroemia
indica
Mariosousa
heterophylla
Parkinsonia
florida
Lysiloma
watsonii
Flowering Not
Flowering
Flowering Not Flowering Flowering Not Flowering Flowering Not Flowering Figure 2.4.3: Comprehensive Method of Selecting New Trees for Vacant Sites SECTION 2: DESIGN & MANAGEMENT PLAN 63
*Washingtonia filifera, California Fan Palm,
can be planted to replace Washingtonia
robusta in designated areas only, as
defined in Figure 2.4.5 p. 65.

Large Space
(unobstructed canopy)
Near underground
utilities
Windy
Location
Normal Wind
Conditions
Ample Root
Space
Deciduous Evergreen
Evergreen
Agonis
flexuosa
Arbutus ‘Marina’
Lyonothamnus
floribundus
ssp. aspleniifolius
Hesperocyparis forbesii
Quercus
fusiformis
Olea europea
Umbellularia
californica
Chilopsis linearis
Chitalpa tashkentensis
Koelreuteria
paniculata
‘Rose Lantern’
Tipuana tipu
Cedrela
fissilis
Prosopis glandulosa
‘Maverick’
Celtis
laevigata
var.
reticulata
Pistacia ‘Red
Push
Agonis
flexuosa
Arbutus
‘Marina’
Lyonothamnus
floribundus
ssp. aspleniifolius
Prunus ilicifolia
ssp. lyonii
Geijera
parviflora
Hesperocyparis forbesii
Lophostemon
confertus
Olea europea
Quercus
fusiformis
Umbellularia
californica
Evergreen,
Not Flowering,
Normal Wind
Conditions
Windy
Location
Ample Root
Space
Evergreen,
Not Flowering Evergreen,
Not Flowering
Deciduous,
Not Flowering Afrocarpus falcatus
Casuarina
cunninghamiana
Quercus
agrifolia Dalbergia
sissoo
Afrocarpus falcatus
Calocedrus
decurrens
Casuarina
cunninghamiana
Quercus
Agrifolia
Flowering Not Flowering Flowering Not Flowering Flowering Not Flowering Normal Wind
Conditions
Dalbergia
sissoo
Calocedrus
decurrens
Casuarina
cunninghamiana
Quercus
Agrifolia
Quercus
Agrifolia
Afrocarpus
falcatus
Afrocarpus
falcatus
Casuarina
cunninghamiana
Pistacia
‘Red Push’
Umbellularia
californica
Olea
europea
Geijera
parviflora
Hesperocyparis forbesii
Lophostemon
confertus
Arbutus ‘Marina’
Prunus ilicifolia
ssp. lyonii
Cedrela
fissilis
Celtis laevigata
var. reticulata
Pistacia ‘Red Push
Chilopsis
linearis
Chitalpa tashkentensis
Tipuana
tipu
Hesperocyparis forbesii
Quercus
fusiformis
Quercus
fusiformis
Olea
europea
Umbellularia
californica
Agonis
flexuosa
Agonis flexuosa
Arbutus
‘Marina’
Arbutus
‘Marina’
Lyonothamnus
floribundus ssp.
aspleniifolius
Lyonothamnus
floribundus ssp.
aspleniifolius
Olea
europea
Celtis laevigata
var. reticulata
Pistacia
‘Red Push’
Prosopis
glandulosa
‘Maverick’
Prosopis glandulosa ‘Maverick’
Chilopsis
linearis
Chitalpa tashkentensis
Koelreuteria
paniculata
‘Rose Lantern’
Pistacia
‘Red Push’
Olea
europea
Prunus
ilicifolia ssp. lyonii
Arbutus
‘Marina’
Koelreuteria paniculata
‘Rose Lantern’
Geijera
parviflora
Acacia
aneura
Callistemon
Ceanothus viminalis
‘Ray Hartman’
Heteromeles
arbutifolia
Malosma laurina
Senna
surattensis
Cercis
occidentalis
Lagerstroemia indica
Mariosousa
heterophylla
Parkinsonia
florida
Lysiloma
watsonii
Yes
Is the site
vacant?
Large Space
(Unobstructed Canopy)
Deciduous, Not Flowering
Evergreen, Not Flowering
Evergreen, Not Flowering
Evergreen, Not Flowering
Windy
Near Underground Utilities
Ample
Root
Space
Normal Wind
Normal Wind
Location
Conditions
Conditions
Deciduous
Deciduous
Evergreen
Medium
Space
(not near power line)
Location
Near Underground Utilities
Not Flowering
Not Flowering
Not Flowering
Flowering
Flowering
Evergreen
Not Flowering
Flowering
Normal Wind
Conditions
Deciduous
Win
d
y Location
Ample
Root
Space
Evergreen
Evergreen
Not Flowering
Flowering
Deciduous
Not Flowering
Normal Wind
Conditions
Flowering
Flowering
Not Flowering
Windy
Not Flowering
Small Space
(small tree well, near building,
power lines, or protected view)
Deciduous
Evergreen
Not Flowering
Flowering
Flowering
Figure 2.4.4: Selection Tree
SECTION 2: DESIGN & MANAGEMENT PLAN 65
source: City of Signal Hill

2.4a Palm Corridors
As noted on Figure 2.4.3 , the detailed tree
selection chart, palm trees are only to be
planted in designated Palm Corridors along
East Spring Street and Cherry Ave. The precise
locations are outlined in green on the map to
the left.
1” = 2,400’
0 1,200 2,400 N
Figure 2.4.5: Palm Corridors & Private Trees
Palm Corridor
66 SIGNAL HILL STREET TREE MASTER PLAN
CalPoly SelecTree
A comprehensive urban
forestry website from the
Urban Forest Ecosystems
Institute (UFEI) at CalPoly
San Luis Obispo. Each entry
in the palette contains a link to its SelecTree
site for more information.

CalScape
An online database of
native California plants by
the California Native Plant
Society.

Calflora
An online database of
California native plants with
search information from
scientific partners.

San Marcos Growers
A nursery located in Santa
Barbara with plentiful
information on their website
and a large selection of
native plants.

Las Pilitas Nursery
A California native plant nursery located in
San Luis Obispo County with information on
Palette Selection
When selecting trees for this palette, many
factors were taken into account. Staff
suggestions as to which trees were thriving
and which caused problems, detailed on pp.
38-41, gave a starting point for specific trees
to include or exclude. Only trees with low-tomedium water use and low-to-moderate root damage potential were considered. All Southern
California Coastal Climate Ready Trees were
included minus the eucalyptus species. Native
species appropriate for street tree use and
with likely nursery availability were also a high
priority. The palette includes many smaller
species so there will be plenty of options
for limited spaces, especially under power
lines. Street tree lists from other California
cities, such as Los Angeles, Long Beach, and
Mountain View, were also consulted. The list is
specifically curated for the City of Signal Hill, its
climate, and its needs.

Resources
In addition to previously mentioned resources
such as Tree People, the Arbor Day Foundation,
and Climate Ready Trees, the following
organizations can provide valuable information
about trees, native plants, and plant care.

This page is not endorsement of associated
businesses, however.

2.5 Street Tree Palette
Selection & Resources
and native plants lists for each California
ecosystem type.

Tree of Life Nursery
A California native plant
nursery with a large
selection of native plants
and useful information on
their website, located in
San Juan Capistrano, CA.

Theodore Payne Foundation
Organization dedicated to
California Native Plants with a
nursery located in Sun Valley,
CA.

Mountain States Wholesale
Nursery
A wholesale nursery located
in Arizona specializing in
water-efficient plants with
an informational website.

Monrovia Nursery
Large nursery with
multiple locations,
including Azusa, CA.

SECTION 2: DESIGN & MANAGEMENT PLAN 67

2.6 Street Tree Palette
Acacia aneura Mulga 20 ft x
15 - 20 ft
2-5' S Very Low Evergreen Medium Low Yes Yes
Afrocarpus falcatus African Fern Pine 40 - 60 ft x
20 - 40 ft
10'+ L Medium Evergreen Medium Low No No
Agonis flexuosa Peppermint Tree 25 - 40 ft x
15 - 25 ft
5-10' M Low Evergreen Strong Moderate No Yes
Arbutus 'Marina' Marina Madrone 40 - 50 ft x
25 - 40 ft
2-5' M Low Evergreen Strong Low No Yes
Callistemon viminalis Weeping Bottlebrush 20 ft x
15 - 20 ft
2-5' S Low Evergreen Medium Low Yes Yes
Calocedrus decurrens Incense Cedar 12 - 200 ft x
30 - 50 ft
10'+ L Very Low Evergreen Medium Moderate No No
Casuarina cunninghamiana River She-Oak 40- 60 ft x
15 - 25 ft
10'+ L Low Evergreen Medium Low No No
Ceanothus 'Ray Hartman' Ray Hartman
Ceanothus
12 - 20 ft x
15 - 20 ft
2-5' S Low Evergreen Medium Low Yes Yes
Cedrela fissilis Brazilian Cedarwood 40 - 60 ft x
40 - 50 ft
10'+ M Medium Deciduous Medium
Weak
Moderate No No
Celtis laevigata var.
reticulata
Netleaf Hackberry 20 - 30 ft x
25 - 30 ft
5-10' M Low Deciduous Medium Low No No
Cercis occidentalis Western Redbud 10 - 20 ft x
10 - 15 ft
2-5' S Low Winter
Deciduous
Medium Low Yes Yes
Chilopsis linearis Desert Willow 12 - 30 ft x
10 - 15 ft
2-5' M Very Low Deciduous Medium Low No Yes
Attributes Scientific Name Common Name
Max Height x
Width
Planting
Width Size
Water
Needs
Deciduous /
Evergreen
Branch
Strength
Powerline
Friendly
Prominent
Flowers
Root Damage
Potential
Climate Ready Tree Native California Tree Very Low Water Use Tree 68 SIGNAL HILL STREET TREE MASTER PLAN
Chitalpa 15 - 30 ft x
15 - 25 ft
5-10' M Low Deciduous Medium
Weak
Medium
Weak
Low No Yes
Dalbergia sissoo Indian Rosewood 40 - 60 ft x
30 - 40 ft
10'+ L Very Low Deciduous Moderate No No
Geijera parviflora Australian Willow 20 - 30 ft x
15 - 20 ft
5-10' M Medium Evergreen Medium Low No No
Hesperocyparis forbesii Tecate Cypress 25 - 30 ft x
20 - 25 ft
5-10' M Very Low Evergreen Strong Moderate Yes No
Heteromeles arbutifolia Toyon 6 - 30 ft x
10 - 15 ft
5-10' S Very Low Evergreen Medium Low Yes Yes
Koelreuteria paniculata
"Rose Lantern"
Rose Lantern
Goldenrain Tree
35 ft x
25 - 40 ft
5-10' M Low Deciduous Medium Low No Yes
Lagerstroemia indica Crape Myrtle 25 ft x
25 ft
2-5' S Low Deciduous Medium Low Yes Yes
Lophostemon confertus Brisbane Box 50 ft x
10 - 30 ft
5-10' M Medium Evergreen Medium Moderate No No
Lyonothamnus floribundus
ssp. aspleniifolius
Santa Cruz Island
Ironwood
25 - 50 ft x
12 - 24 ft
5-10' M Very Low Evergreen Strong Moderate No Yes
Lysiloma watsonii Feather Bush 15 ft x
12 - 15 ft
2-5' S Low Partly
Deciduous
Partly
Deciduous
Low Yes No
Malosma laurina Laurel Sumac 10 - 20 ft x
10 - 20 ft
2-5' S Very Low Evergreen Low Yes Yes
Mariosousa heterophylla Palo Blanco 20 ft x
12 - 15 ft
2-5' S Very Low Weak
Weak
Low Yes Yes
Medium
Weak
Attributes Scientific Name Common Name
Max Height x
Width
Planting
Width Size
Water
Needs
Deciduous /
Evergreen
Branch
Strength
Powerline
Friendly
Prominent
Flowers
Root Damage
Potential
Chitalpa tashkentensis
Climate Ready Tree Native California Tree Very Low Water Use Tree SECTION 2: DESIGN & MANAGEMENT PLAN 69
Attributes Scientific Name Common Name
Max Height x
Width
Planting
Width Size
Water
Needs
Deciduous /
Evergreen
Branch
Strength
Powerline
Friendly
Prominent
Flowers
Olea europea Olive Tree 30 ft x
25-30 ft
5-10' M Low Evergreen Strong Low No No
Parkinsonia florida Blue Palo Verde 25 ft x
15 - 20 ft
5-10' S Very Low Deciduous Medium Low Yes Yes
Pistacia ‘Red Push’ Red Push Pistache 40 ft x
20 - 40 ft
5-10' M Medium Deciduous Strong Low No No
Prosopis glandulosa
‘Maverick’
Maverick Mesquite 35 ft x
25 - 35 ft
5-10' M Low Deciduous Medium Low No Yes
Prunus ilicifolia ssp. lyonii Catalina Cherry 25 - 40 ft x 20 -30 ft
5-10' M Very Low Evergreen Medium Low No Yes
Quercus agrifolia Coast Live Oak 25 - 80 ft x
15 - 35 ft
10'+ L Low Evergreen Strong Moderate No No
Quercus fusiformis Escarpment Live Oak 50 ft x
20 - 40 ft
10'+ M Medium Evergreen Strong Moderate No No
Quercus tomentella Island Oak 30 - 70 ft x
35 ft
10'+ L Low Evergreen Strong Moderate No No
Senna surattensis Kolomona 25 ft x
20 - 25 ft
5-10'
5-10' S Low Evergreen Medium Low Yes Yes
Tipuana tipu Tipu 50 ft x
25 - 50 ft
10'+ M Medium Partly
Deciduous
Weak Moderate No Yes
Umbellularia californica California Laurel 6 - 80 ft x
3 - 30 ft
10'+ M Low Evergreen Strong Moderate No No
Washingtonia filifera California Fan Palm 70 ft x
10 - 20 ft
M Low Evergreen Medium
Strong
Moderate No No
Root Damage
Potential
Climate Ready Tree Native California Tree Very Low Water Use Tree 70 SIGNAL HILL STREET TREE MASTER PLAN
Acacia aneura
Mulga
Family: Fabaceae
Afrocarpus falcatus
African Fern Pine
Family: Podocarpaceae
Agonis flexuosa
Peppermint Tree
Family: Myrtaceae
Native Range: Western Australian Mulga
shrublands
Shape: Rounded
Foliage Type: Evergreen
Size: 20' x 15-20'
Planting Area: 2-5'
Water Use Rating: Very Low
Growth Rate: Moderate
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: Yes
Leaves: Bluish Green or Silver or Gray Green; Alternate, Simple; Linear
Bark: Dark Brown or Light Green, Fissured
Litter: Dry Fruit
Flowers/Fruit: Small, yellow, bottle brush-shaped flower clusters in spring; brown seed pods in summer-fall.

Notes: Climate Ready Tree
Native Range: Eastern South Africa, Swaziland,
Mozambique, and Zimbabwe
Shape: Rounded
Foliage Type: Evergreen
Size: 40-60' x 20-40'
Planting Area: 10'+
Water Use Rating: Medium
Growth Rate: Moderately Fast
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: No
Leaves: Deep Green; Alternate, Simple; Linear
Bark: Light Gray, Furrowed, Smooth
Litter: Dry Fruit
Flowers/Fruit: Inconspicuous flowers; small yellow fruit resembling olives in fall.

Notes: Medium water use
Native Range: Western Australia
Shape: Rounded or Vase, Weeping
Foliage Type: Evergreen
Size: 25-40' x 15-25'
Planting Area: 5-10'
Water Use Rating: Low
Growth Rate: Moderately Fast
Branch Strength: Medium
Root Damage Potential: Moderate
Powerline Friendly: No
Leaves: Green; Alternate, Simple; Spear-shaped
Bark: Red Brown, Exfoliating, Furrowed
Litter: Dry Fruit
Flowers/Fruit: White, fragrant flowers in spring; small, brown, cone-like fruit
Notes:

CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/14 CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/1113 CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/143 S L M
Photos: CalPoly SelecTree Photos: F & K. Starr; CalPoly SelecTree Photos: CalPoly SelecTree SECTION 2: DESIGN & MANAGEMENT PLAN 71
Arbutus 'Marina'
Marina Madrone
Family: Ericaceae
Callistemon viminalis
Weeping Bottlebrush
Family: Myrtaceae
Calocedrus decurrens
Incense Cedar
Family: Cupressaceae
Native Range: Hybrid of Mediterranean & British
Isles species
Shape: Rounded or Vase
Foliage Type: Evergreen
Size: 40-50' x 25-40'
Planting Area: 2-5'
Water Use Rating: Medium
Growth Rate: Moderate
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: No
Leaves: Green; Alternate, Simple; Elliptic
Bark: Red Brown, Exfoliating, Smooth
Litter: Wet Fruit
Flowers/Fruit: Clusters of small, pink, bell-shaped flowers; edible red fruit resembling strawberries
Notes: Medium water use; fruit can be messy; standard version best for street trees; Arbutus unedo acceptable substitution Native Range: Eastern Australia
Shape: Rounded, Weeping
Foliage Type: Evergreen
Size: 20' x 15-20'
Planting Area: 2-5'
Water Use Rating: Low
Growth Rate: Moderately Fast
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: Yes
Leaves: Green; Alternate, Simple; Spear-shaped
Bark: Dark Gray, Exfoliating, Striated
Litter: Dry Fruit
Flowers/Fruit: Bright red, large, bottle brush-shaped flowers blooming in spring/summer
Notes: High biogenic emissions
Native Range: California, Western North America
Shape: Conical
Foliage Type: Evergreen
Size: 12-200' x 30-50'
Planting Area: 10'+
Water Use Rating: Very Low
Growth Rate: Slow
Branch Strength: Medium
Root Damage Potential: Moderate
Powerline Friendly: No
Leaves: Deep Green; Opposite, Simple; Scale-like
Bark: Red Brown, Fibrous, Furrowed
Litter: Dry Fruit
Flowers/Fruit: Small cones in fall/summer.

Notes: California native, found mostly in mountainous areas; large
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/174 CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/241 CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/243 M S L
Photos: CalPoly SelecTree Photos: E. Gilman; CalPoly SelecTree Photos: S. Patel; CalPoly SelecTree 72 SIGNAL HILL STREET TREE MASTER PLAN
Casuarina cunninghamiana
River She-Oak
Family: Fabaceae
Ceanothus 'Ray Hartman'
Ray Hartman Ceanothus
Family: Rhamnaceae
Cedrela fissilis
Brazilian Cedarwood
Family: Meliaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/275 CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/282 CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/285 Native Range: California
Shape: Rounded
Foliage Type: Evergreen
Size: 12-20' x 15-20'
Planting Area: 2-5'
Water Use Rating: Low
Growth Rate: Moderately Fast
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: Yes
Leaves: Deep Green; Alternate, Simple; Oval
Bark: Brown, Smooth
Litter:

Flowers/Fruit: Clusters of small, blue-purple flowers in spring; small, berry-like capsules in winter or summer
Notes: California native; single-trunk standard variety trained with higher first branches best for street tree use
Native Range: Australia
Shape: Rounded
Foliage Type: Evergreen
Size: 40-60' x 15-25'
Planting Area: 10'+
Water Use Rating: Low
Growth Rate: Moderate
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: No
Leaves: Bluish Green or Silver or Gray Green ; Whorled, Simple; Linear
Bark: Dark Gray to Brown, Fissured
Litter: Dry Fruit
Flowers/Fruit: Small brown cones in spring.

Notes: Large. Not an oak. Also called Horsetail Tree, Australian Pine.

Native Range: Brazil, Paraguay
Shape: Rounded
Foliage Type: Deciduous
Size: 40-60' x 40-50'
Planting Area: 10'+
Water Use Rating: Medium
Growth Rate: Moderately Fast
Branch Strength: Medium Weak
Root Damage Potential: Moderate
Powerline Friendly: No
Leaves: Green, new growth has red tinge; fall color; Alternate, Pinnately Compound; Spear-shaped
Bark: Dark Brown, Dark Gray, Light Gray or Light Green, Smooth Litter: Dry Fruit
Flowers/Fruit: Clusters of small white bells in spring followed by pear-shaped brown cones that split into star shape
Notes: Climate Ready Tree
L S M
Photos: CalPoly SelecTree Photos: CalPoly SelecTree; Las Pilitas Nursery Photos: L. Correa; CalPoly SelecTree; SECTION 2: DESIGN & MANAGEMENT PLAN 73
Cercis occidentalis
Western Redbud
Family: Fabaceae
Chilopsis linearis
Desert Willow
Family: Bignoniaceae
Native Range: California foothills, Arizona, Utah
Shape: Rounded
Foliage Type: Deciduous
Size: 10-20' x 10-15'
Planting Area: 2-5'
Water Use Rating: Medium
Growth Rate: Moderately Fast
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: Yes
Leaves: Bright Green to Blue-Green; Alternate, Simple; Oval Bark: Gray to Brown
Litter: Dry Fruit
Flowers/Fruit: Small magenta blossoms along branches, brown seed pods
Notes: California native; medium water use; standard version trained with single stem and higher branches best for street trees
Native Range: California, Texas, Mexico
Shape: Rounded
Foliage Type: Deciduous
Height: 12-30' x 10-15'
Planting Area:2-5'
Water Use Rating: Very Low
Growth Rate: Moderately Fast
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: No
Leaves: Green; Alternate, Simple; Linear
Bark: Light Green to Light Gray, Exfoliating
Litter: Dry Fruit, Flowers
Flowers/Fruit: Pink, trumpet-shaped flowers in spring; long, thin seed pods in fall
Notes: California native; standard version trained with single stem and higher branches best for street trees; 'Bubba' cultivar acceptable substitute and CRT Inland but not Coastal
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/321 CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/345 Celtis laevigata var. reticulata
Netleaf Hackberry
Family: Cannabaceae
Native Range: California; riparian areas of the
Southwest US
Shape: Rounded
Foliage Type: Deciduous
Size: 20-30' x 25-30'
Planting Area: 5-10'
Water Use Rating: Low
Growth Rate: Moderate
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: No
Leaves: Green, yellow fall color; Alternate, Simple; Ovate Bark: Mottled, Light Gray or Red Brown, Smooth
Litter: Dry Fruit
Flowers/Fruit: Inconspicuous fruit in spring; small, red-orange drupe in fall
Notes: California native, Climate Ready Tree; has excellent survival readings in CRT study; needs pruning to maintain shape CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/301 M S M
Photos: University of Arizona; CalPoly SelecTree Photos: G. Castriotta; CalPoly SelecTree Photos: L. Lukes, L. Kling, P. Breen 74 SIGNAL HILL STREET TREE MASTER PLAN
Chitalpa tashkentensis
Chitalpa
Family: Bignoniaceae
Native Range: hybrid between desert willow &
catalpa (Southern US)
Shape: Rounded or Vase
Foliage Type: Deciduous
Size: 15-25' x 15-25'
Planting Area: 5-10'
Water Use Rating: Low
Growth Rate: Fast
Branch Strength: Medium Weak
Root Damage Potential: Low
Powerline Friendly: No
Leaves: Green; Opposite, Simple; Linear
Bark: Light Green to Light Gray, Scaly
Litter: Flowers
Flowers/Fruit: Lavender, trumpet-shaped flowers in spring Notes: "Pink Dawn" or "Morning Cloud" both acceptable
cultivars
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/1488 Dalbergia sissoo
Indian Rosewood
Family: Fabaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/483 Native Range: Indian Subcontinent
Shape: Rounded or Vase
Foliage Type: Deciduous
Size: 40-60' x 30-40'
Planting Area: 10'+
Water Use Rating: Very Low
Growth Rate: Moderate
Branch Strength: Medium Weak
Root Damage Potential: Moderate
Powerline Friendly: No
Leaves: Green; Alternate, Pinnately Compound; Oval
Bark: Dark Brown or Light Green, Furrowed, Rough
Litter: Dry Fruit, Flowers
Flowers/Fruit: Small white or yellow flowers in spring; seed pods in fall
Notes: Climate Ready Tree; wide-spreading roots help control erosion
Geijera parviflora
Australian Willow
Family: Rutaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/654 Native Range: Australia
Shape: Rounded
Foliage Type: Evergreen
Size: 20-30' x 15-20'
Planting Area: 5-10'
Water Use Rating: Medium
Growth Rate: Moderately Fast
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: No
Leaves: Green; Alternate, Simple; Spear-shaped
Bark: Dark Brown or Light Green, Rough
Litter: Dry Fruit
Flowers/Fruit: Small white flowers in spring; small green capsules in fall
Notes: Medium water use
M L M
Photos: CalPoly SelecTree Photos: CalPoly SelecTree Photos: PlantMaster; CalPoly SelecTree SECTION 2: DESIGN & MANAGEMENT PLAN 75
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/697 Heteromeles arbutifolia
Toyon
Family: Rosaceae
Native Range: California
Shape: Rounded or Vase
Foliage Type: Evergreen
Size: 6-30' x 10-15'
Planting Area: 5-10'
Water Use Rating: Very Low
Growth Rate: Moderate
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: Yes
Leaves: Dark Green; Alternate, Simple; Oblong
Bark: Dark Brown, Dark Gray or Light Gray, Smooth
Litter: Wet fruit
Flowers/Fruit: Clusters of small white flowers in summer; clusters of small, bright red berries in fall-winter
Notes: California native; naturally mounding shrub form but can be pruned
Hesperocyparis forbesii
Tecate Cypress
Family: Cupressaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/472 Native Range: California
Shape: Columnar or Rounded
Foliage Type: Evergreen
Size: 20-30' x 15-25'
Planting Area: 5-10'
Water Use Rating: Very Low
Growth Rate: Fast
Branch Strength: Strong
Root Damage Potential: Moderate
Powerline Friendly: Yes
Leaves: Green; Whorled, Simple; Scale-like
Bark: Dark Brown or Red Brown, Exfoliating, Scaly, Smooth Litter: Dry Fruit
Flowers/Fruit: Small cones
Notes: California native, Climate Ready Tree; 'Greenlee's Blue Rocket' cultivar a taller and narrower alternative. Did not perform well in coastal sites in CRT study—DO NOT
OVERWATER.

Koelreuteria paniculata 'Rose Lantern'
Rose Lantern Goldenrain Tree
Family: Sapindaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/780 Native Range: China
Shape: Rounded
Foliage Type: Deciduous
Size: 35' x 25-40'
Planting Area: 5-10'
Water Use Rating: Low
Growth Rate: Moderately Fast
Branch Strength: Medium Weak
Root Damage Potential: Low
Powerline Friendly: No
Leaves: Green; Alternate, Pinnately Compound; Oval
Bark: Dark Brown or Light Green, Fissured
Litter: Dry Fruit
Flowers/Fruit: Clusters of small yellow flowers in spring; pink seed capsules (lanterns) in fall
Notes: Goldenrain tree and K. elegans are acceptable
substitutes; K. bipinnata also acceptable but susceptible to shot-hole borer; have higher water rating than "Rose Lantern" M S M
Photos: Theodore Payne Foundation; CalPoly SelecTree Photos: Channel Islands Research; CalPoly SelecTree Photos: Harvard Arboretum; CalPoly SelecTree 76 SIGNAL HILL STREET TREE MASTER PLAN
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/1425 Lophostemon confertus
Brisbane Box
Family: Myrtaceae
Native Range: Australia
Shape: Rounded
Foliage Type: Evergreen
Size: 50' x 10-30'
Planting Area: 5-10'
Water Use Rating: Medium
Growth Rate: Moderately Fast
Branch Strength: Medium
Root Damage Potential: Moderate
Powerline Friendly: No
Leaves: Green; Alternate/Whorled, Simple; Ovate
Bark: Striking, Light Green, Red Brown or Multicolored, Exfoliating, Smooth
Litter: Dry Fruit, Flowers
Flowers/Fruit: Clusters of small, star-shaped flowers in spring, small brown or red capsules in summer
Notes: Medium water use
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/790 Lagerstroemia indica
Crape Myrtle
Family: Lythraceae
Native Range: China
Shape: Rounded or Vase
Foliage Type: Deciduous
Height: 25' x 25'
Planting Area: 2-5'
Water Use Rating: Low
Growth Rate: Moderate
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: Yes
Leaves: Green, edges can be tinged red or bronze; fall color; Alternate, Simple; Oval
Bark: Light Green, Pink or Red Brown, Exfoliating, Smooth Litter: Dry fruit
Flowers/Fruit: Clusters of showy flowers; several colors available including white, pink, and lavender
Notes: Multi- or single-stemmed; Several cultivars acceptable, including 'Catawba,' 'Cherokee,''Potomac,' and 'Powhatan' Lyonothamnus floribundus ssp. aspleniifolius
Santa Cruz Island Ironwood
Family: Rosaceae
Native Range: California
Shape: Conical or Rounded
Foliage Type: Evergreen
Size: 25-50' x 12-24'
Planting Area: 5-10'
Water Use Rating: Very Low
Growth Rate: Moderate
Branch Strength: Strong
Root Damage Potential: Moderate
Powerline Friendly: No
Leaves: Dark Green; Opposite, Pinnately Compound; Oblong Bark: Striking, Light Gray or Red Brown, Exfoliating, Smooth, Striated
Litter: Dry Fruit, Flowers
Flowers/Fruit: Clusters of small white flowers in summer; small brown capsules in fall
Notes: California native, Catalina Ironwood also acceptable CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/832 S M M
Photos: R. Rasthan; ASU; CalPoly SelecTree; Photos: JMK; CalPoly SelecTree Photos: G. Castriotta; CalPoly SelecTree SECTION 2: DESIGN & MANAGEMENT PLAN 77
Lysiloma watsonii
Feather Bush
Family: Fabaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/834 Native Range: Arizona
Shape: Rounded or Vase
Foliage Type: Deciduous
Size: 15' x 12-15'
Planting Area: 2-5'
Water Use Rating: Low
Growth Rate: Moderate
Branch Strength: Medium Weak
Root Damage Potential: Low
Powerline Friendly: Yes
Leaves: Green; Alternate, Bipinnately Compound; Oblong
Bark: Dark Gray or Light Gray, Rough, Scaly
Litter: Dry fruit
Flowers/Fruit: Small white puffballs in spring; large brown seed pods in fall
Notes: Climate Ready Tree
Malosma laurina
Laurel Sumac
Family: Anacardaceae
CalScape: https://calscape.org/loc-California/Malosma-laurina- (Laurel-Sumac)?srchcr=sc634889672331d
Native Range: California
Shape: Rounded, Shrub
Foliage Type: Evergreen
Size: 10-20' x 10-20'
Planting Area: 2-5'
Water Use Rating: Very Low
Growth Rate: Fast
Branch Strength: Low
Root Damage Potential: Low
Powerline Friendly: Yes
Leaves: Green with red tinge; Alternate, Simple; Lance-shaped Bark: Gray to Reddish, Smooth
Litter: Dry Fruit, Flowers
Flowers/Fruit: Clusters of small white flowers in spring; small white drupe in fall
Notes: California native; shrub, not tree, but very hardy and drought-tolerant, provides deep shade; can be pruned to shape Mariosousa heterophylla
Palo Blanco
Family: Fabaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/1578 Native Range: Mexico, Sonoran Desert
Shape: Weeping
Foliage Type: Partly deciduous
Size: 20' x 2-15'
Planting Area: 2-5'
Water Use Rating: Very Low
Growth Rate: Moderate
Branch Strength: Weak
Root Damage Potential: Low
Powerline Friendly: Yes
Leaves: Bluish Green or Silver or Gray Green; Alternate, Simple; Linear
Bark: Cream or White, Exfoliating, Smooth
Litter: Dry fruit
Flowers/Fruit: Cylindrical clusters of fringed flowers in summer followed by large brown seed pods
Notes: Climate Ready Tree; Also called "Acacia willardiana" or "Mariosousa willardiana;" weak branch strength
S S S
Photos: M. Dimmit; ASU; CalPoly SelecTree Photos: P. Vellieux, G. Castriotta; SMMNRA Photos: CalPoly SelecTree 78 SIGNAL HILL STREET TREE MASTER PLAN
Olea europaea
Olive Tree
Family: Oleaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/970 Native Range: Mediterranean
Shape: Rounded or Vase
Foliage Type: Evergreen
Size: 30' x 25-30'
Planting Area: 5-10'
Water Use Rating: Low
Growth Rate: Medium
Branch Strength: Strong
Root Damage Potential: Moderate
Powerline Friendly: No
Leaves: Bluish Green or Silver or Gray Green; Opposite, Simple; Ovate
Bark: Light Gray, Scaly
Litter: Wet Fruit, Dry Fruit
Flowers/Fruit: Inconspicuous flowers in spring; edible fruit in fall
Notes: Low-fruit or fruitless cultivars include "Majestic Beauty" and "Swan Hill;" "Mission" bears fruit but is hardy, developed by Spanish missionaries in California
Parkinsonia florida
Blue Palo Verde
Family: Fabaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/309 Native Range: Southern California, Arizona,
Mexico
Shape: Rounded
Foliage Type: Deciduous
Size: 25' x 15-20'
Planting Area: 5-10'
Water Use Rating: Very Low
Growth Rate: Moderately fast
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: Yes
Leaves: Bluish Green or Silver or Gray Green; Alternate, Pinnately Compound; Oval
Bark: Green or Red Brown, Exfoliating, Smooth
Litter: Dry fruit
Flowers/Fruit: Yellow flowers in spring followed by brown seed pods
Notes: California native; thorny; 'Desert Museum' available as thornless cultivar and CRT inland; drought deciduous
Pistacia ‘Red Push’
Red Push Pistache
Family: Anacardiaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/1604 Native Range: Hybrid developed in Arizona of
species from China and Persia
Shape: Rounded or Vase
Foliage Type: Deciduous
Size: 40' x 20 - 40'
Planting Area: 5-10'
Water Use Rating: Medium
Growth Rate: Moderately slow
Branch Strength: Strong
Root Damage Potential: Low
Powerline Friendly: No
Leaves: Green, deep red when emerging in spring, fall color; Alternate, Pinnately Compound; Spear-shaped
Bark: Dark Brown, Light Gray or Light Green, Furrowed, Scaly Litter: Leaves
Flowers/Fruit: Inconspicuous fruit in spring followed by small clumps of red berries
Notes: Climate Ready Tree; winter deciduous; P. chinensis acceptable substitute.

M S M
Photos: CalPoly SelecTree Photos: D. Seibert; L. Makings, L. Landrum Photos: G. McPherson, Tucson Clean & Beautiful, Treeland Nurseries SECTION 2: DESIGN & MANAGEMENT PLAN 79
Prosopis glandulosa ‘Maverick’
Maverick Mesquite
Family: Fabaceae
Prunus ilicifolia ssp. lyonii
Catalina Cherry
Family: Rosaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/1605 CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/1164 Native Range: California Channel Islands
Shape: Rounded
Foliage Type: Evergreen
Height: 30-50' x 1 0-20'
Planting Area: 5-10'
Water Use Rating: Very Low
Growth Rate: Moderate
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: No
Leaves: Dark Green; Alternate, Simple; Spear-shaped, serrated edges
Bark: Dark Brown, Fissured
Litter: Wet Fruit
Flowers/Fruit: Bottle brush-shaped white flower clusters in spring; red cherries in summer
Notes: California native, Climate Ready Tree; Hollyleaf Cherry is acceptable substitute
Native Range: Cultivar from Southwestern U.S.

Shape: Rounded
Foliage Type: Deciduous
Size: 35 x 25-35'
Planting Area: 5-10'
Water Use Rating: Medium
Growth Rate: Moderately Fast
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: No
Leaves: Green; Alternate, Bipinnately Compound; Linear
Bark: Grey, Smooth
Litter: Dry Fruit, Leaves
Flowers/Fruit: Yellow catkins in spring; large brown seed pods in fall
Notes: Climate Ready Tree; winter deciduous
Quercus agrifolia
Coast Live Oak
Family: Fagaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/1227 Native Range: Central & Southern California
Shape: Rounded
Foliage Type: Evergreen
Size: 25-80' x 15-35'
Planting Area: 10'+
Water Use Rating: Low
Growth Rate: Moderate
Branch Strength: Strong
Root Damage Potential: Moderate
Powerline Friendly: No
Leaves: Dark Green; Alternate, Simple; Oval
Bark: Dark Gray, Furrowed, Smooth
Litter: Dry Fruit
Flowers/Fruit: Inconspicuous flowers in spring; acorns in fall Notes: California native; Native CA oaks have protected legal status and may require permits for trimming or removing M M L
Photos: CalPoly SelecTree Photos: M. Bush, Z. Akulova; CalPoly SelecTree Photos: T. Russell; CalPoly SelecTree 80 SIGNAL HILL STREET TREE MASTER PLAN
Quercus tomentella
Island Oak
Family: Fagaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/1484 Native Range: California Channel Islands
Shape: Rounded
Foliage Type: Evergreen
Size: 30-70' x 35'
Water Use Rating: Low
Growth Rate: Moderate
Branch Strength: Data Not Available
Root Damage Potential: Data Not Available
Powerline Friendly: No
Leaves: Dark Green; Alternate, Simple; Ovate
Bark: Dark Gray / Brown, Blocky, Smooth
Litter: Dry Fruit
Flowers/Fruit: Inconspicuous flowers in spring; acorns in fall Notes: California native, Climate Ready Tree; Native CA oaks have protected legal status and may require permits for trimming or removing; suitable for monolithic sites
Quercus fusiformis
Escarpment Live Oak
Family: Fagaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/1608 Native Range: South-Central United States,
Mexico
Shape: Rounded
Foliage Type: Evergreen
Size: 50' x 20-40'
Planting Area: 10'+
Water Use Rating: Medium
Growth Rate: Slow
Branch Strength: Strong
Root Damage Potential: Moderate
Powerline Friendly: No
Leaves: Dark Green; Alternate, Simple; Oval
Bark: Black or Dark Brown, Blocky, Furrowed, Scaly
Litter: Dry Fruit
Flowers/Fruit: Inconspicuous flowers in spring; acorns in fall Notes: Climate Ready Tree; medium water use
Senna surattensis
Kolomona
Family: Fabaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/269 Native Range: Australia and Southeast Asia
Shape: Rounded
Foliage Type: Evergreen
Size: 25' x 20-25'
Planting Area: 5-10'
Water Use Rating: Low
Growth Rate: Moderate
Branch Strength: Medium
Root Damage Potential: Low
Powerline Friendly: Yes
Leaves: Green; Alternate, Pinnately Compound; Oblong
Bark: Gray, Smooth
Litter: Dry Fruit, Leaves, Flowers
Flowers/Fruit: Clusters of bright yellow flowers, followed by long brown seed pods
Notes: Synonym for Cassia surattensis
M L S
Photos: ASU; CalPoly SelecTree Photos: D. Gress; CalPoly SelecTree Photos: CalPoly SelecTree SECTION 2: DESIGN & MANAGEMENT PLAN 81
Tipuana tipu
Tipu
Family: Fagaceae
Umbellularia californica
California Laurel
Family: Lauraceae
Washingtonia filifera
California Fan Palm
Family: Arecaceae
CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/1419 CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/1446 CalPoly SelecTree: https://selectree.calpoly.edu/tree-detail/1470 Native Range: Bolivia and Southern Brazil
Shape: Rounded
Foliage Type: Deciduous
Height: 50' x 25-50'
Planting Area: 10'+
Water Use Rating: Medium
Growth Rate: Moderate
Branch Strength: Medium Weak
Root Damage Potential: Moderate
Powerline Friendly: No
Leaves: Light Green; Alternate, Pinnately Compound; Oblong Bark: Dark Brown or Light Green, Fissured
Litter: Dry Fruit, Flowers
Flowers/Fruit: Bright yellow flowers in summer; samara in fall Notes: Medium water use, weak branch strength
Native Range: California
Shape: Rounded
Foliage Type: Evergreen
Size: 6-80' x 3-30'
Planting Area: 10'+
Water Use Rating: Low
Growth Rate: Moderate
Branch Strength: Strong
Root Damage Potential: Moderate
Powerline Friendly: No
Leaves: Green; Alternate, Simple; Spear-shaped
Bark: Dark Brown, Fissured
Litter: Dry Fruit
Flowers/Fruit: Small, fragrant yellow flowers in spring; cherrysize, green to purple drupe in summer Notes: California native; medium water use
Native Range: Southeastern California and
Northern Mexico
Shape: Palm
Foliage Type: Evergreen
Size: 70' x 10-20'
Planting Area: 5-10'
Water Use Rating: Low
Growth Rate: Moderate
Branch Strength: Medium Strong
Root Damage Potential: Moderately Fast
Powerline Friendly: No
Leaves: Dark Green; Alternate, Palmately Compound
Bark: Red Brown, Furrowed, Smooth
Litter: Dry Fruit, Large Leaves
Flowers/Fruit: Clusters of small white flowers in spring; clusters of small dark drupe in fall
Notes: California native; "skirts" need trimming; only for planting in designated spots as indicated on flow chart; replacement for Washingtonia robusta
M M M
Photos: D. Gress; CalPoly SelecTree Photos: G. Smith; CalPoly SelecTree Photos: University of Arizona; CalPoly SelecTree 82 SIGNAL HILL STREET TREE MASTER PLAN
and to supply usable quantities once a species
is proven. The city might also contract to
have nurseries provide oaks and other native
species grown from local genetic stock rather
than those developed elsewhere in California.

Monitor pests and diseases within Signal
Hill and neighboring communities. To
prepare for problems which may entail largescale removal and replacement of trees, the City should actively monitor all major pest
and disease populations, both locally and
regionally, that could adversely affect its
forest. Preparations should then include special
preventative health care of targeted tree
species to help them withstand the disease,
pest or other threat.

Foster age diversity by immediately
replacing trees as they are removed.

Replacement at removal will create a
staggered-age new generation providing more
or less continuous tree cover.

Anticipate removals and plan for plantings
accordingly. To properly monitor age diversity,
a useful life expectancy must be established
for each species. This describes approximately
how long the tree can be expected to remain
in a healthy and vigorous condition, before
serious decline sets in. At that point, the
Monitor overall species and age diversity.

The city staff must keep track of the
percentages of each species in the city and
assess where imbalances may be developing.

This monitoring will be a primary use of the
city’s tree inventory, with assessments made
periodically.

Encourage planting a variety of species and
cultivars. When a species begins to be overplanted, the City should discourage its use and recommend alternative species. A variety
of cultivars of a single species might also
be appropriate, if each is known to possess
tolerances to certain conditions not found in
the others. Although environmental stresses
that are predictable will be selected against, a
range of adaptability in the tree stock ensures
against unanticipated problems. In general, the
city as a whole should contain no more than
10% of any species, no more than 20% of any
genus, and no more than 30% of any family.

Test new species and cultivars for wider
application. The City should actively seek
to expand its palette of acceptable trees
by test-planting species not widely planted
here and monitoring their performance. Since
availability is often a limiting factor to the use
of new species, the City could contract with
nurseries both to provide experimental stock
This section outlines the major strategies for
managing the community forest, many of which
have been adapted from classical forestry
for use in the urban environment. While the
recommendations are for the entire community
forest, they can and should be applied to
Signal Hill's street trees. These guidelines are
intended to assist city staff in monitoring and
managing the rates of planting and removal
and the overall composition of the forest.

Policy makers, business people, developers and
residents will find these strategies of interest
since they set the context for day-to-day
decisions affecting the forest.

From the perspective of the long-term health
and appearance of the community forest,
maintaining a diversity of tree species and
ages is vital. A diverse forest, like a diverse
natural ecosystem or a diversified economy,
is likely to be more stable than a simple one.

Should a pest, disease, climatic occurrence
or other problem cause the removal of an
entire species, diversity provides insurance
against the kind of wholesale denuding of the
forest cover that took place in many eastern
communities with the invasion of Dutch elm
disease.

2.7 Management Guidelines
SECTION 2: DESIGN & MANAGEMENT PLAN 83
trees, removals are an essential part of
the overall care of the forest. Establishing
clear criteria and a well-defined process for
determining removals will help ensure that this
aspect of forest management is accepted by
the community.

In general, trees in a city should be allowed
to grow to the maximum age possible. Unlike
traditional forestry management, where
value is measured by monetary return when
harvested, the value of city trees comes from
their ability to grow old and large, providing
shade and beauty. As a part of routine
maintenance, all trees will be monitored for
hazardous conditions.

The relationship between timely removals and
the long-term health of the forest cannot be
overemphasized. Educating the community
about the benefits of a managed forest is
essential to avoid problems later on. Meeting
with environmental groups to explain city
management policies, as well as informing the
public about tree removal criteria, will help the
tree removal process proceed more smoothly.
expense of maintaining the tree in a pleasing
and non-hazardous condition may exceed the
benefits it provides. Its removal should then be
considered, although the final decision should
be subject to the removal evaluation process
per the latest city policies.

Keep the inventory current. In order to gain
the full benefits of the inventory, it is essential
that each servicing of a tree be recorded in
the inventory, together with an updating of
the information about the tree to reflect any
change in its status or condition. An accurate
inventory will serve as the nerve center of a
forestry effort which maximizes both program
efficiency and forest benefits.

Inform the residents of the horticultural
needs of trees fronting their property,
especially for drought-tolerant species in
parking strips in front of houses.

Removing Trees
Tree removal is perhaps the most sensitive
decision to be made regarding the community
forest. The depth of people’s attachment to
trees and the benefits associated with them
become clear when one is slated for removal.

However, when seen in the context of the
lifecycle of the forest, and when complemented
by vigorous efforts to preserve and replant
Management Guidelines
• Monitor overall species and age
diversity.
• Encourage planting a variety of
species and cultivars.
• Test new species and cultivars for
wider application.
• Monitor pests and diseases
within Signal Hill and neighboring
communities.
• Foster age diversity by
immediately replacing trees as
they are removed.
• Anticipate removals and plan for
plantings accordingly.
• Keep the inventory current.
• Inform the residents of the
horticultural needs of trees
fronting their property.

3.0 PLANTING & MAINTENANCE
SECTION 3: PLANTING & MAINTENANCE 85
This chapter describes the actual installation of
a tree, an event which is the culmination of the
careful process of site and species selection.

Proper planting techniques can greatly affect
the lifelong health of the tree. The location
for planting a tree has been determined.

Underground utilities have been identified and
the planting area sited so that the tree will
not be in conflict with them. An appropriate
species has been selected which meets the
design guidelines, matches the environmental
conditions, and fits the size of the planting
area. The tree has been acquired and is ready
for planting.

The time of year when the tree is planted has
a major impact on the long-term success of
a tree. Installation of trees during the months
of November and December will facilitate
movement of new roots in the surrounding soil
before the hot weather arrives, and thereby
accelerate the establishment of the tree in
its new soil environment. It will also save on
maintenance costs since much of the watering
during the first four to five months will be
taken care of by the winter rains. This timing
has such a significant effect on the proportion
of success in establishment of new trees
that sincere efforts should be made to avoid
planting street trees at any other time of the
year than late fall.

By contrast, the worst time to install street
trees is mid-spring through summer, when the
maximum demand for moisture is taking place.

At this time, it is most difficult to resupply
moisture to the root mass as fast as it is
being used by the foliage canopy of the tree.

Transplant success ratios for trees installed
during these months are significantly less than
for those installed in early winter.

When spring or early summer planting is
necessary, the following steps must be taken:
• Soak the rootball in wetting agent before
removal from the container.
• Fill the planting hole with water and let
settle before planting.
• Check rootball moisture at least once per
week.

3.1a Guidelines for Tree Planting

1. Contact utility companies to locate
underground utilities and call DigAlert, 811.

2. Obtain the necessary permit.

3. Notify nearby property owners if they have
not been previously notified.

4. Gather tools and materials needed (see the
checklist which follows).

5. Set up safety barricades.

6. Prepare the planting area.

7. Cut the pavement, if needed.

8. Dig the planting area.

9. Check for soil and drainage problems.

10. Add special materials such as root control
barriers or drainage materials.

11. When possible, include modular suspended
pavement support system (see "Modular
Suspended Pavement Systems" in Appendix
for details).

12. Fill the area with backfill and water to allow
settlement overnight.

13. Check for drainage problems the next day. If
water has not drained, choosing a different
planting location is highly recommended.

14. Dig planting holes and plant and water the
tree.

15. Install non-wire stakes and tree ties.

16. Add mulch over the planting area.

17. Place paving materials, tree guards and
tree grates if required.

18. Clean up.

Record the tree planting in the city inventory
database.

Standard tree planting details for Signal Hill
are included on pages 95-97. Recommended
changes to these guidelines are included in
Section 2: Design & Management Plan.

3.1 Planting the Tree
86 SIGNAL HILL STREET TREE MASTER PLAN

3.1b Checklist for Planting
tree wells that do not meet these standards
must be widened by cutting the concrete.

Soil is purposely compacted in urban areas
to facilitate construction of pavement and
buildings. In construction work a stable surface
which will not settle is desired. Soil is usually
compacted to 95% of the possible maximum.

When trees grow in compacted soil their access
to oxygen is limited, and both percolation and
drainage of water are slowed. A tree’s roots
cannot absorb needed nutrients without
sufficient aeration and good moisture levels.

In addition, compacted soils discourage deep
rooting.

Often trees grown near pavement in
compacted soil will put their roots under the
hardscape as they seek water and air. (Shallow
irrigation can also be a factor in this, and some
tree species are naturally shallow rooted and/
or aggressive in their rooting habits.) Moisture
tends to collect under pavement, and the
gravel layer often present there is a source of
air. The temperature under pavement is often
less vulnerable to extreme changes than the
temperature of soil exposed to air. Creating a
large, uncompacted planting area and providing
good drainage and aeration will all help mitigate
the problem of compaction. Preparing the
planting area allows soil compaction to be
lowered from the usual 95% to a maximum of
85%. Using a backhoe or power auger greatly

3.1c Preparing the Planting Area
The lifespan of a street tree planted in typical
urban conditions (i.e., a 36” square planting
hole surrounded by extensive paving, with
frequent pedestrian traffic) can be as brief
as ten years. Providing the largest available
amount of uncompacted soil section for growth
is the most important factor in helping a tree
grow to maturity.

Make the planting area as wide as possible
Most tree roots grow horizontally in the first
12” of soil below finish grade. Larger planting
areas (6ft. by 6ft.) are recommended on major
streets and wherever possible. Parkways and

The Basics
‡ Trees
‡ Source of water
‡ People-power
Power Tools
‡ Concrete saw cutter
‡ Backhoe
‡ Auger
‡ Dump truck
Hand tools
‡ Mattock
‡ Planting bar
‡ Shovel
‡ Stake pounder
‡ Broom
‡ Can snips
‡ Gloves
Materials
‡ Mulch
‡ Backfill
‡ Gravel
‡ Modular suspended pavement support
system
‡ Water retaining polymer
‡ Water wetting agent
‡ Fertilizer
‡ PVC perforated drainpipe, 36” min.
lengths
‡ Tree stakes
Checklist for Planting
SECTION 3: PLANTING & MAINTENANCE 87
eases the task of digging the planting hole. If
the hole is dug with an augur, the walls must be
roughened with a planting bar to allow roots to
penetrate the soil after the tree is planted.

Trees require about 1.5 to 2 cubic feet of loam
soil per square foot of canopy area, defined
as the area within the mature diameter of the
trees canopy spread. An industry rough rule
of thumb is that 1,000 cubic feet of loam soil
is the minimum required, but this is still not
sufficient to support a large mature tree such
as an Oak or Plane tree. (See Figure 3.1.1 from
page 205 of Up By Roots by James Urban) There
are many optional approaches to adding loam
soil under pavement, each is different in its
effectiveness. Stone based structural soil only
contains 20% loam soil and thus requires 5,000
cubic feet of material to get to the 1,000 cubic
feet minimum. Sand based structural soils have
limited testing and have not performed nearly
as well as loam soil. The most efficient system
is to increase the loam soil under pavement by
using a modular suspended pavement system
filled with unscreened loam soil.

Locate Underground Utilities
Every home and business in Signal Hill is
served by public utilities: water, wastewater,
gas, electric, telephone, and cable television.

Wastewater laterals are particularly susceptible
to damage and stoppages due to root intrusion
by trees and even large shrubs, especially in
times of drought. This results in both added and
unnecessary costs to the city as well as the
individual property owners.

Underground Utilities
Figure 3.1.2: Underground Utilities. Be careful to check for underground utilities before planting a new tree.

Figure 3.1.1: Tree Size to Soil Volume Ratio, James Urban 88 SIGNAL HILL STREET TREE MASTER PLAN
as alkalinity, poor drainage, rocks or debris,
or compaction. These conditions must be
remedied prior to planting.

Alkalinity may be found by looking at color.

Gray or white soil usually indicates an alkaline
condition. The use of alkaline-tolerant species
is recommended.

Poor drainage can be identified by filling a
planting hole with water and seeing how long
it takes to drain. If water in the hole has not
settled at least one inch in one hour, do not
plant before special drainage preparations are
tried. If the water has not drained overnight, a
new planting location should be chosen. Also
check the species selected to be sure it will
grow in poorly drained soil. If not, contact the
Public Works Director or designated personnel.

Visual inspection of the soil by digging a pit,
using a soil probe or simply finding an exposed
area can give more specific information about
a site. Particle size, moisture content, and
rockiness can be appraised.

The soil on construction sites is often
compacted - either unintentionally, due to the
movement of heavy equipment and materials,
or deliberately, to help the soil bear the weight
of buildings and pavement. These compacted
soils can create conditions similar to both
bedrock and hardpan, especially when the
existing soil has a high clay content. Trees
should never be planted in soils which have a
compaction rate higher than 85%.

If compaction is severe, a breaker bar may
be needed to loosen the soil or drill through
hardpan. (See the following section on
improving drainage.)
Backfill
When preparing and planting trees in clay
soils, do not add soil amendments unless
special conditions require it, such as highly
alkaline soil. Although organic materials can
improve the structure and permeability of any
soil, if you add a large quantity to a planting
hole in clay soil you can, in effect create an
underground “container” for a new tree’s roots.

Upon reaching the perimeter of the planting
hole and its soft, permeable, conditioned soil,
roots will then run into dense native clay and
have difficulty penetrating it. Excess water
also collects in the amended planting hole,
waterlogging the root zone and possibly killing
the tree from lack of air in the soil.

In clay soils, the backfill mix should be native
soil which has been loosened by excavation
of the planting area. Water immediately after
City crews and/or property owners must
contact the various utility companies prior to
scheduling planting to determine the location
of their respective utility laterals prior to
digging. The location of a water service lateral
is usually obvious because the water meter
should be visible at the ground surface. This is
not, however, true with the other utilities. It is
not uncommon to dig or drill directly into a gas
main or wastewater lateral. People may not be
aware that they have hit a wastewater lateral
and unknowingly plant their tree, resulting in
possible flooding at a later date. There is also
potential danger from cutting into a gas main
(resulting in explosions or fire), or electrical
conduit (causing shock or electrocution).

Planting in Tree Wells
Cutting existing pavement may be needed to
create an adequate tree well. This work requires
the use of heavy equipment and should only be
done by city crews or an appointed contractor
with a permit from the city. A diamond saw
cutter, jackhammer, backhoe, loader and dump
truck may all be required depending on the
situation.

Check For Soil and Drainage Problems
While digging and preparing the planting
area, it is recommended that you check for
any adverse or unusual soil conditions such
SECTION 3: PLANTING & MAINTENANCE 89
placing the backfill in the planting area and
tamp to settle the backfill and add soil as
necessary to achieve finish grade before
digging planting hole.

Soil amendments and/or import soil should only
be used in the case of highly alkaline native
soils. The use of amendments or improved soil
mixes in the planting pit of a newly planted
tree can create a sharp boundary between
“improved” and native soils, inhibiting roots
from venturing beyond the boundary and
inhibiting water movement into the pit. The
use of natural soil, without amendments, is
preferred.

Laboratory analysis. For large plantings, soil
samples from several spots on the site should
be submitted to a professional soil laboratory.

The resulting chemical and particle size
analysis gives both the makeup of the soil and
recommendations for corrective measures and
appropriate plants.

Improving Drainage
Constantly wet soil prevents active root
growth. Various methods for assuring
acceptable drainage in the planting area should
be used. In the very worst cases, where no
percolation takes place, and the layer creating
the problem is too thick to drill through, planter
holes must be thought of as bathtubs. A drain
line must run from the bottom of the “bathtub”
to a common drain.

Where a hardpan layer is encountered, drill
numerous 2” diameter holes through the
hardpan. This can be accomplished using
pneumatic tools such as an air spade/ air
knife, or a mechanical auger. In clay soils which
drain slowly but in which the topsoil is at least
6 ft. deep and continuous, irrigation should
be thorough and infrequent. If water does not
drain when tested while preparing the planting
area, 6” diameter holes augured to a depth of
2 ft. minimum, and filled with gravel, may help
keep water away from the roots. In deeper soils
with an uninterrupted soil profile to a depth
of 10 ft. or more, no drainage arrangements
should be needed.

Clay
Sand
Silt
Figure 3.1.3: USDA Soil Types. Source: Wikimedia, Carrie Lapolla 90 SIGNAL HILL STREET TREE MASTER PLAN

3.1d Preparing Planting Holes and
Placing the Tree
After the planting areas have been prepared,
drainage and root barrier systems have been
installed, and the back fill has been well settled,
the planting holes are dug and the trees
planted.

Container Grown Trees
Do not plant the tree until the buttress roots
have been found. Tree nurseries often grow
trees too deeply in the container soil mix. Trees
whose buttress roots are not visible are at high
risk of developing roots that girdle (strangle)
the trunk. Take time to pull away any soil that
is covering the buttress roots. The exposed
and visible buttress roots should be planted at
grade, or 1-2 inches above grade. Plant the tree
when the root ball is moist. Dry root balls are
tough to moisten once planted, and overly wet
root balls may fall apart during planting.

1. Dig the planting hole at least twice as wide
as the root ball, and only as deep as the
root ball.

2. Remove the tree from the container,
carefully supporting the root ball from
below. Trees should never be handled by the
trunks (except bare-root trees). Handle all
trees by their containers or root balls.

3. Check the root ball for signs of being
rootbound. Reject any badly rootbound
trees, or trees with kinked roots.

Otherwise, sever any circling or matted
roots with a saw, sharp shears, or a knife.

4. Set the tree in the planting hole so that the
buttress roots are at grade, or 1-2 inches
above grade. (The tree will settle to grade
when watered.)

5. Fill in about half the hole with backfill and
soak the soil. When the water has drained
away, fill in the rest of the planting hole.

6. Form a watering basin of the same
diameter as the root ball, and fill up the
basin three times, letting the water drain
each time
Bare Root

1. Soak the tree’s roots in water or keep
them in a moist plastic bag while preparing
planting hole.

2. Form a mound or cone of soil in the center
of the planting hole.

3. Place the roots of the tree on this mound,
carefully spreading them out at their
natural angles. Roots should fit the planting
hole without bending or cutting them.

4. Plant the tree with its buttress roots at
grade, or 1-2 inches above grade.

5. With the tree positioned on the cone of soil,
fill in about half of the hole with backfill soil
Root Control Barriers
The recommended minimum planting area is 4
ft. by 8ft. Root control devices should be used
whenever the tree must be in a 48” square
or smaller opening of a pavement area. They
should also be used when a tree is planted in
an area adjacent to pavement, within 5 ft. of
the pavement. Any tree species, in most soils,
will eventually damage surrounding pavement
in openings less than 36” square without root
control, and many will cause damage in areas
of less than 48”. While barriers help direct
the tree’s root growth downward, they should
not be thought of as removing the need for
proper species selection. An alternate method
of root control is to use a bio barrier. This is a
geotextile fabric (a synthetic textile which can
be placed underground) impregnated with an
herbicide.

Trees in Turf Areas
In turf areas, when appropriate, trees are to be
installed with a 3 x 3 ft. wood header to keep
turf away from the tree trunk. Lawn mowers
and string-trimmers cause tremendous
destruction of the cambium layer, and must be
kept away from tree trunks.

SECTION 3: PLANTING & MAINTENANCE 91
and soak the soil.

6. When the water has drained away, fill in the
rest of the planting hole with more backfill
and water it. If the tree settles too low in
the process, you can raise it to the proper
position while the soil is moist by grasping
it firmly and gently, lifting it up with a sideto-side rocking motion until it is at the proper height.

7. Apply more soil and water until the tree
remains at the correct level.

8. Form a watering basin which is the same
diameter as the root system, and fill up the
basin three times, letting the water drain
each time.

Ball and Burlap

1. Soak the root ball thoroughly with a water
one to two days before installation.

2. Do not plant the tree until the buttress
roots have been found. Tree nurseries often
grow trees too deeply in the field soil. Trees
whose buttress roots are not visible are
at high risk of developing roots that girdle
(strangle) the trunk. Take time to pull away
any soil that is covering the buttress roots.

3. The exposed and visible buttress roots
should be planted at grade, or 1-2 inches
above grade.

4. Dig a planting hole twice the diameter of
the root ball and the same depth as from
the bottom of the root ball to the buttress
roots.

5. Place the tree in the planting hole. Verify
that the buttress roots are at grade, or 1-2
inches above grade.

6. Remove as much of the burlap and metal
cage as possible without the root ball falling
apart. Bolt cutters are useful for removing
the metal cage and a box cutter is useful
for removing the burlap.

7. Fill the hole to half its height with backfill
soil and water. When the water has drained
away, fill in the rest of the planting hole with
more backfill and water it.

8. Form a watering basin which is the same
diameter as the root ball, and fill up the
basin three times, letting the water settle
in between soakings.

Figure 3.1.6: Trees from Nurseries. Trees may come in just their roots, in a container, or with their roots wrapped in burlap.
92 SIGNAL HILL STREET TREE MASTER PLAN
trees planted bare root may not need staking.

However, some nursery-grown trees will need
staking for stability and protection from injury.

As support stakes for five-gallon to 24-inch
box trees, install two 2” diameter (or 2” by 2”)
stakes per tree, tall enough for the particular
tree. Install the stakes outside the root ball and
a minimum 30” below grade to ensure stability.

Supplemental stakes for anchoring the root ball
or for protection should be 3 ft. long, with half
the length of the stake below grade. Support
stakes should be perpendicular to the prevailing
wind direction. A 1” by 3” cross bar in may be
added for stability. On windy sites where the
wind comes from several directions, a threestake system may be needed.

Ties should be flexible to allow for growth of
the trunk. Wire ties should never be used.

Install ties at one point only, at 6” above the
natural bend point of the tree. To find the bend
point, remove the nursery stake (the small
stick attached to the trunk at the nursery) and
pull the top of the crown to one side, holding
the trunk with one hand. The point on the
trunk where the canopy will snap back to an
upright position by itself is the natural bend
point. Pruning the tree at planting time, when
indicated, will lighten the weight of the canopy
and raise the natural bend point.

Cut the tops of the stakes so that they are only
2” to 3” taller than the point where the ties are
placed. This prevents the top of the tree from
rubbing against the stakes in strong winds.

The nursery stake should usually be removed
at planting time. However, if the trunk is too
weak to stand without the stake, it should be
cut and reattached as an auxiliary stake. The
auxiliary stake should be attached 2” above
the root ball and no higher than 24” from the
tip of the tree’s central leader. An even better
auxiliary support in this case would be a flexible
spring steel rod (or other flexible support stake
such as fiberglass or bamboo) extending from
2” above the root ball to 6” above the natural
bend point of the tree. The rod should be 1/4”
diameter for five-gallon containers and 3/8”
diameter for fifteen-gallon containers. Tie the
rod to the trunk with one-inch-wide plastic
tape at 6” to 10” on center. Auxiliary stakes do
not take the place of support stakes. Their sole
purpose is to help strengthen and straighten
the trunk while allowing movement.

Ties should contact the trunk with a broad
surface to minimize rubbing or girdling, and
they should have some elasticity. Wire should
never be used. Elastic webbing, tire cording,
or heavy polyethylene tape (for small trees)
can be used. The tie should be loosely looped

3.1e Staking the Tree
The purpose of staking is to stabilize the
root ball until the roots can anchor the tree,
supporting the trunk in an upright position,
and protecting the trunk from injury. Whenever
possible, it is better to not stake a tree if it
can stand without one. The tree will develop
a strong trunk in a shorter period without
staking. Conifers, upright growing trees, and
Slow-release irrigation bags, such as the Treegator
pictured above, can be installed at planting. These bags prevent water waste from runoff and allow the tree to be watered weekly. Photo: treegator.com
SECTION 3: PLANTING & MAINTENANCE 93
around the trunk. Two ties, one from each
stake, should be used.

Larger trees, 36” box or larger, may require
a guying system for anchorage. The least
hazardous method for pedestrians is an
underground auger anchor, such as Duckbill
earth anchors. Above grade guy wires should
not be used.

For small trees which may need protection
against weed competition and human and
machine damage, trunk guards may be used.

Trunk guards should be made of stiff materials
that hang loosely around the trunk, which
prevents trunk constriction and prevents
moisture from being trapped against the trunk.

Trunk protection tubes are often made of
plastic.

3.1f After the Tree is in Place
A 4”-deep layer of shredded bark or bark chips
should be spread over the entire planting area
outside the watering basin at planting time
wherever possible, to conserve soil moisture,
inhibit weed growth, and prevent baking of
the soil by the sun. Mulch will also improve
soil fertility and soil structure as it degrades
into the soil. For trees in tree wells or narrow
planting strips, where mulch would tend to spill
out on the pavement, it may be necessary to
use a thinner layer. Shredded bark is preferable
on slopes as it has less tendency to slip than
bark chips. Mulch should never be in contact
with the tree trunk and be kept clear of the
buttress roots.

Placing Paving Materials
Paving materials laid flush with the soil in a
tree well generally cause compaction and limit
access for watering, but they are a better
method than planting in smaller cutouts. They
will also cause trunk damage and girdling if in
constant contact with the trunk. In high-traffic
areas, where the planting areas need to be
diminished to allow for pedestrian movement,
use a tree grate or other self-supporting
system which does not compact the soil.

Where new paving is installed, it should slope
away from the planting area so that excess
runoff does not drain toward the tree in the
winter. Water from paved surfaces also carries
alkaline chemicals and motor oil residue into
the soil.

When possible, install a modular suspended
pavement support system per manufacturer’s
most recent recommendations prior to
replacing or installing new pavement.

Installing Tree Guards and Grates
In high-traffic areas more protection is needed
for young trees. In some cases, aesthetics
may demand iron tree guards, but they must
be removed as the tree matures or they will
strangle the tree.

Perforated iron tree grates or precast concrete
tree covers with perforations may be used if
they are self-supporting above the soil. The
perforations allow air and water to reach the
soil. The grates must be expandable (by means
of knock-out sections) to allow for trunk
growth. Pea gravel is the recommended mulch
material when tree grates are used.

Placing mulch around a street tree. Photo: canopy.org
94 SIGNAL HILL STREET TREE MASTER PLAN
Turf and Ground Covers
Turf and ground covers should not be installed
within a tree’s watering basin, as they will
compete with the tree for nutrients; the tree
may also suffer damage from mowers and
string-trimmers. Frequently when trees are
planted, ground cover is kept at least 3 or 4
ft. from the tree. However, sometimes the
aesthetic benefit of ground cover, or the need
to protect or enhance trees in high traffic
areas, outweighs the problem of competition
for nutrients. This is a design decision that
needs to made for each situation.

Cleaning Up
The work area should be swept, debris removed,
and tools returned. The new tree should be
entered into the street tree database.

3.1g Why Trees Sometimes Die After
Planting
• Lack of water.
• Overwatered, soggy soil.
• Insufficient preparation of the planting
area, so that soil compaction is not
corrected.
• Failure to correct alkalinity in the soil and to
plant an alkaline-tolerant species.
• Loss of roots from overly severe root
pruning (roots are often pruned to
compensate for a root bound condition in
containers) or from a root ball breaking
apart when handled.
• Drying of roots from exposure to sunlight
before planting, in bare root trees.
• Air pockets, stones, or hard clumps in the
soil which prevent contact of the roots with
the soil.
• Crowding of the roots into too small a
planting hole.

Dead street trees can be avoided. Photo: S. Bloch
SECTION 3: PLANTING & MAINTENANCE 95

3.1h Signal Hill Standard Tree Planting Details
Note: new revisions will
supersede all included details.

Figure 3.1.7: Signal Hill Public Works Tree Well Detail, Plan (211) Figure 3.1.8: Signal Hill Public Works Parkway Street Tree Planting Detail, Section (212) 96 SIGNAL HILL STREET TREE MASTER PLAN
Figure 3.1.9: Signal Hill Public Works Parkway Street Tree Planting Detail (212) Figure 3.1.10: Signal Hill Public Works Parkway Street Tree Planting Detail, Notes (212) SECTION 3: PLANTING & MAINTENANCE 97
Figure 3.1.11: Signal Hill Public Works Parkway Street Tree Planting Detail, Section (212A) Figure 3.1.12: Signal Hill Public Works Parkway Street Tree Planting Detail, Plan (212A) 98 SIGNAL HILL STREET TREE MASTER PLAN
Tree stumps should be removed promptly to prevent the
spread of pests. Photo: G. Castriotta
These infestations can spread to nearby live
trees. Stumps should be removed to a depth of
24” for most trees.

3.2c Tree Watering
No absolute rule exists that will tell you
precisely how often to water trees. Watering
frequency will be influenced by the type of tree,
weather conditions, soil type, root competition
from other plants, and how well the tree is
established.

A basic goal of this the Master Plan is to plant
trees which are compatible with the natural
water cycles Southern California. Most of the
trees on the recommended list will survive on
normal rainfall once they are established.

Proper tree irrigation creates a root zone that
will be moist enough to encourage growth of
new roots but not so wet that air is continually
excluded from the soil pore space, which
hampers growth. In addition, proper irrigation
should encourage deep root penetration
that can sustain a tree in dry periods. This
also keeps the tree from developing shallow
roots which can crack pavement. Infrequent,
slowly applied, deep watering is the best way
to accomplish these goals. Frequent light
sprinklings or surface irrigation, such as turf
watering, will discourage deep rooting. A
plastic, and leave stored for at least 6 months.

It is inappropriate to transport infected firewood
outside of city limits and depending on type of
pest and local regulations, may be illegal.

Trees infected with the shot hole borer must
also be handled differently. Wood should be
chipped to help limit the spread of the beetle/
fungus complex. Wood should be chipped to
pieces smaller than 1”. Unchipped logs should be
stacked into small piles and treated by solarizing/
tarping under clear plastic.

Stump Removal
Stumps should be ground out or pulled out even
if they aren’t in the way of replanting. They
provide sites for insect infestations and fungus
infections, particularly the fungus Armillaria
mellea (honey mushroom fungus). Pine stumps
are also attractive to the pine bark beetle, and
the California turpentine beetle. Eucalyptus
stumps can harbor eucalyptus longhorn beetle.

3.2 Maintaining the Tree

3.2a Pruning
Regular maintenance and pruning is to be carried
out by the contracted arborist. Currently, the
city trims by grid. It is recommended that the
city adopt a species-based trimming schedule;
however, due to budget constraints, staff
recommends to prune/trim on a biannual
basis with the exception of sudden growths or
unforeseen circumstances. Additionally, trees
are not to be pruned to protect or enhance a
view.

3.2b Tree Removals
All trees eventually will need to be removed due
to old age, disease, death, or problems with
hardscape destruction. Removal of any tree of
15 feet in height or more is a procedure which,
like tree pruning, should have the supervision of
a qualified tree specialist. Tree climbers should
have an ISA Climber’s Certificate and on-thejob rope training. It is a dangerous operation requiring specialized knowledge and equipment,
and care must be taken to avoid injury to workers
or the public, or damage to property.

Limb and Branch Removal
Wood infected with wood boring insects such
as shot hole borer, eucalyptus longhorn beetle,
or pine bark beetle must be handled differently
because of insect problems. Chip, bury, burn, or
tarp all infected wood. Tarp with 6 mil thick clear
SECTION 3: PLANTING & MAINTENANCE 99
new 15-gallon tree will need to have the soil
moistened to a depth of at least 12”, and a
mature tree to a depth of at least 24” with
each irrigation.

Newly installed trees can easily have their root
balls dry out, even when the surrounding soil
is very wet. Care must be taken to make sure
that water is getting to the root ball by making
the watering basin of a newly installed tree the
same size as the root ball.

The use of a mulch around the tree is
recommended to slow the evaporation of water.

A 4” layer of shredded bark or bark chips will
help retain moisture and discourage weed
growth. Most standards call for a 2” minimum
layer, but recent studies show that a 4” layer
is 5 times more effective in retaining moisture
and discouraging weed growth. In tree wells and
narrow planting strips where there might not
be enough room for the full 4” depth, install as
deep a layer as possible without spilling over.

Note: mulch should never be placed against the
trunk of the tree or root flare.

Using a soil probe to determine the soil
moisture content in the root zone is the most
effective way to schedule watering. If the soil is
wet enough to make a solid, firm ball, the tree
should not be watered. It is also important to
begin irrigating in the spring before the soil has
dried out, in order to make use of the reservoir
of water from the winter rains. It requires much
less irrigating to replace the water lost through
a week of evapotranspiration than it does to
totally recharge the planting area reservoir.

Watering Frequency Guidelines
These guidelines assume average weather
conditions and rainfall, and are for all trees
during establishment regardless of species
water preferences.

For the first 2 to 3 weeks after planting:
• New trees may require water every 2-4
days, especially in hot weather. In winter,
container-grown evergreens need water at
least once a month.

First year:
• Fall and spring: once weekly
• Summer: twice weekly
Second year:
• Fall and spring: twice monthly
• Summer: once weekly
Third year:
• Once a month during the dry season
Fourth year and after:
• Two waterlogs during the entire dry season,
if needed.
• Drought tolerant trees often do not need
Table 19 Infiltration Rates
Soil Texture Infiltration Rate
(Inches/Hour)
Sand 1-10
Sandy Loam .5-3
Loam .3-.8
Clay Loam .1-.6
Clay .01-0
Table 20 Soil Moisture
Amount of Moisture Feel or Appearance of Soil
Close to 0% field
capacity. Little or no
moisture available
Sandy loam: dry, loose; flows through
fingers
Clay foam: Somewhat crumbly; will hold
together with pressure
50-75%. Enough
available moisture.

Sandy loam: Tends to ball under
pressure but will seldom hold together.

Clay loam: Forms a ball; somewhat
plastic; may stick slightly with pressure
75%. Plenty of
available moisture.

Sandy loam: Forms weak ball; breaks
easily.

Clay loam: Forms a ball, very pliable
100 SIGNAL HILL STREET TREE MASTER PLAN
Automatic irrigation: While most of Signal
Hill's street tree sites do not currently have
irrigation, the city should add irrigation lines
as a requirement for new development and
include street tree irrigation line with new
city construction projects and sidewalk
improvements. Hard pipe bubblers connected
to a weather based, smart irrigation controller.

Hard pipe bubblers are municipal-friendly
considering that they are easy to work on, can
be inspected easily, deliver a sufficient amount
of water in minimal time, and do not cause
overspray.

It is necessary to change the location and
number of emitters as the trees mature, so
that water continues to get to the feeder roots
around the driplines of the trees. As a tree
grows, emitters should be placed so that, at a
minimum, an area between the dripline and 3 ft.
toward the trunk from the dripline is irrigated (if
the tree continues to need irrigation).

Irrigation Repair
Any irrigation system needs to be monitored
to make sure it is operating properly. The
most obvious and important sign is plant
material that looks unhealthy. Too much or too
little water should be one of the first things
considered when this occurs.
“Automatic” systems are not maintenance
free, and need care in terms of programming
to fit weather conditions, and monitoring to
see that the system is working properly. This is
particularly important since most systems are
programmed to run in very early morning. This
means that the system will go on when no one
is there to see how it’s functioning. Periodic
“early bird” inspections are needed to check
the functioning of the systems. In systems
which cover a large area, it may be helpful to
use a clock which can be controlled by a remote
control device. Inspections, adjustments, and
repairs can be made without having to travel
back and forth from the clock to the area being
worked on.
any further irrigation.
• In times of drought, a normal watering
program may not be possible, even if
the regular program has been a careful,
conserving one. It will be most important in
these times to give a deep watering at the
beginning of the dry season. Established
drought-tolerant trees should be able
to survive the dry season with just one
watering.

Methods of Irrigation
By hand with a hose: Care should be taken to
water long enough to soak the root ball deeply.

Flow through the hose should be gentle enough
that it does not destroy the watering basin
or compact the soil. A mulch helps prevent
compaction.

With a water truck: One unit with a one or
two person crew can efficiently irrigate many
trees. This is the most cost- effective method,
since most trees will need only infrequent
irrigation once established. A watering truck
typically provides water to sidewalk cutouts,
and community trees where there is no existing
irrigation (no meter). It is recommended that
the city purchase a watering truck if the budget
allows.

Street tree being watered. Photo: City of Vancouver
SECTION 3: PLANTING & MAINTENANCE 101
The irrigation systems should be monitored
for problems with sprinkler heads, which are
commonly of three kinds. Either the riser has
been broken off and needs to be replaced, or
the sprinkler is blocked by foliage which needs
to be pruned away from the head, or the head
has be come clogged and needs to be removed
and cleaned out. Sometimes a head only needs
to be adjusted to get better coverage, but it
may be that the adjustment is needed because
of partial clogging, so this should be checked.

Frequent clogging may be a sign of a small
break in the pipe. A broken pipe can cause
large amounts of water to be wasted. Usually
the problem will be obvious, with a telltale area
of standing water and mud. When a sprinkler
head needs to be replaced, if the identical
head is not available it is important that the
replacement has a similar precipitation rate
and radius of throw. Manufacturer’s catalogs
will have this information. Another common
problem is a stuck valve, which can prevent the
water from shutting off at the end of a cycle.

This can result in the waste a large amount
of water in a short time if not reported, as
well as overwatering of the plants. Most valve
manufacturers sell replacement kits for the
innards of the valve. Valves should always
be installed with a union connection to the
pipe, so they can be more easily removed and
replaced.

When a valve doesn’t open, or doesn’t close,
it can sometimes take some troubleshooting
to determine if the problem is caused by a
valve or controller. Most controller problems
are not fixable in the field, since most modem
controllers are solid-state computerized
models. The clock will need to be replaced or
fixed at the factory. Care must be taken if
automatic controllers are used, that if power
failures interrupt the programs, the clocks are
reprogrammed. Most controllers have battery
backups, but the batteries must be replaced
every year.

When valves, controllers, heads, and other
equipment need to be replaced, it is important
that the quality of the replacement parts be
at least equal to the original parts. If poorquality parts have been used originally, the quality should be upgraded when the parts are
replaced.

When irrigation repair is needed, often the
repair crew will need to refer to the as-built
drawings in order to locate various components
of the system. It is important that accurate
as-built plans are filed with the city when an
irrigation system is constructed.

Watering During Drought
Signs of Drought Stress:
• Wilting of leaves and shoots
• Less deep green leaves
• Smaller than normal leaves
• Early leaf drop and thinning canopy
• Browning of leaf edges
Steps to Improve a Tree’s Drought Tolerance:
• Remove turf (lawn/grass) from under the
dripline as turf competes for soil moisture.
• Remove any impervious surfaces as they
impair the movement or water, nutrients
and air into the soil.
• Decompact the soil within the dripline using
a garden fork, air tool or auger. This adds
holes that create air circulation within the
soil.
• Install four inches of organic mulch under
the dripline, improving root growth and soil
condition, reducing weeds and the need for
water by conserving moisture.
• Do not remove or turn off turf irrigation
that is also watering a tree. Slowly reduce
the amount of irrigation or replace it with
another watering method.
• Monitor and adjust to save water by
measuring soil moisture. Provide soil
moisture to 18-24” beneath as much of
the dripline as possible. A soil probe used
one to two hours after watering should be
102 SIGNAL HILL STREET TREE MASTER PLAN
Tree with damaged roots. Photo: B. Hagen
Trenching
Utilities and footings for buildings and walls
should be designed and located to minimize
disturbance to tree roots. If a footing must
be laid near a tree, use only pier and grade
beam footings with bridge foundations within
the dripline. Do not use a continuous grade
beam footing. Dig 30” deep pilot holes with a
two-man power auger, using an 8” bit. If roots
of 4” in diameter or greater are encountered,
move the proposed location of the pier 12”. If
utility lines must travel through a dripline the
trenches must be dug by hand. Tunnel under
any roots encountered rather than cutting the
roots. Trenching under oaks can only legally be
done with hand tools.

Root Damage
Avoid encroachments, cutting, and filling
within the dripline whenever possible. If roots
over 1” are broken, cut the root cleanly and
immediately cover the cut with a plastic bag
tied with a rubber band or tape. No oak roots
over 1” may legally be cut.

Watering
If one-quarter or more of a tree’s roots will
be disturbed, a special watering schedule is
necessary. The tree should be watered before
construction begins. The tree will need 10
gallons of water for each 1” of tree caliper,
applied to a minimum depth of 12” over the
outer half of the dripline area. Continue
watering once a month during the dry season.

Drainage and Erosion Control
If grading alters the drainage patterns, be sure
that water is directed away from the trunks of
the trees to prevent fungus infections.

Paving
Consider use of modular suspended pavement
system where applicable.

Pests & Diseases
The following pages list common pests and
diseases to look for.
able to penetrate into the soil to a depth of
12” fairly easily. The soil should feel slightly
damp and be darker in color.
• Continue to monitor the tree’s health,
consider increasing the frequency and/
or watering volume if it continues to show
signs of drought stress.

3.2d Protection of Existing Trees
Before construction work is undertaken near
existing trees, procedures for protection of the
trees should be understood. Specific procedures
for protection during and after construction
should be agreed upon and approved by the
Public Works Director or designee. It is important
to realize that the result of damage to the root
system of the tree may appear anywhere from
five to fifteen years after the work has been
done.

The following guidelines are basic tree protection
practices. The city may require additional
conditions as part of their plan review or permit
process.

Compaction
Do not compact the soil any closer than 5 ft. out
from the dripline of any tree during construction
(the tree’s “protected zone”). Fence off the tree
at the outermost edge of the protected zone
before any equipment is allowed on the site.

SECTION 3: PLANTING & MAINTENANCE 103
M. Fratino
104 SIGNAL HILL STREET TREE MASTER PLAN

COMMON PESTS & DISEASES

TREE PROBLEM
Acacia species chlorosis in alkaline soils
Callistemon species, Bottlebrush chlorosis in alkaline soils Celtis occidentalis, Common hackberry caterpillars
Cercis occidentalis, Western redbud water molds, Rhizoctoria root rot, black stem fungus
Cinnamomum camphora, Camphor tree honey mushroom fungus verticillium wilt Cupaniopsis anacardioides, Carrotwood aphids in the spring Eriobotrya deflexa, Bronze loquat firehlight, black scale Erythrina caffra, Coral tree caterpillars in summer
Eucalyptus species lime-induced chlorosis in alkaline soil, Eucalyptus longhorn borer
Fraxinus velutina glabra, Modesto ash ash anthracnose, ash curl aphid, honey mushroom fungus
Geijera parviflora, Australian willow occasional black scale Jacaranda mimositolia, Jacaranda caterpillars in the spring Lagerstroemia indica, Crape myrtle mildew (new hybrids are resistant) Ligustrum lucidum, Glossy privet black scale
Liquidambar styraciflua, American
sweetgum
brown softshell scale
Magnolia grandiflora, Southern magnolia aphids in spring Olea europaea, Olive black scale, Pseudomonas syringa canker Pinus canariensis, Canary Island pine pine bark aphid, pine needle aphid Pinus halapensis, Aleppo pine pine bark aphid, pine needle aphid western pine rust gall, Sequoia pitch moth, severe
spider mite

TREE PROBLEM
Pinus thunbergiana, Japanese black pine pine bark aphid, pine needle aphid Pinus radiata, Monterey pine pine bark beetle, California turpentine beetle, pine bark aphid, pine needle aphid,
western pine rust galls, sequoia pitch moth,
very severe spider mite
Prunus caroliniana, Carolina cherry laurel chlorosis in alkaline soils Prunus caroliniana, Purple plum shot hole fungus, water mold fungi (in over-wet soils), plum leaf aphid (in variety
‘Bijeriana’)
Pyrus calleryana varieties, Ornamental pear check for fireblight Quercus agrifolia, Coast live oak fruit tree leaf roller, oak leaf caterpillar, oak twigborer, oak tree hopper, honey
mushroom fungus
Schinus molle, California pepper pepper tree psyllid
Schinus terebinthifolius, Brazilian pepper verticillium wilt Tipuana tipu, Tipu tree aphids
Tristania conferta, Brisbane box chlorosis
Ulmus parvifolia, Chinese elm elm anthracnose, elm leaf beetle SECTION 3: PLANTING & MAINTENANCE 105

DIAGNOSIS

TIPS FOR DIAGNOSING TREE PROBLEMS CAUSED BY PESTS
By C. S. Koehler
Cooperative Extension, U.C. Berkeley

1. More then half of the problems brought to your attention will be attributable to factors other than insects and mites.

2. The cause of poor plant performance may not be evident on the plant sample given to you for diagnosis. The cause may lie farther down the plant.

3. The mere presence of insects or mites does not always mean that they are the real cause of poor plant performance. (Improper maintenance or poor plant selection also contribute.)

4. If the entire tree is dead, the chances are great that insects or mites were not the cause of death. Insects and mites seldom kill their host plants.

5. Most insects and mites show specificity in their choice of plants. Some are general feeders, but most are not. Knowing the name of the affected plant is therefore extremely helpful in determining the identity of the offending insect or mite, because lists of pests and other references are often organized by host plant.

6. The application of a pesticide is not the solution to every problem.

7. By the time many people notice a pest problem and seek your advice, it is often too late in the season to take corrective action.

8. Especially when reporting by telephone, people tend to magnify the actual size of an insect.

9. Insects and mites must feed in order to survive and reproduce. Evidence of their feeding will nearly always remain on the plant after the pest is gone. Most signs and symptoms of pest activity fit into one or more of the categories listed in this table.

Symptom or Sign Probable Pest Resopnse
I. Chewed leaves, blossoms Caterpillars, beetles, sawflies, snails, slugs. Also leafminers (chewing is
inside leaf)
II. Stippled, bleached, yellowed, or
bronzed leaves
Leafhoppers, aphids, psyllids, thrips,
lace bugs, spider mites
III. Distortion (twisting, cupping,
swelling of plant parts)
Thrips, aphids, blister (bud) mites,
gallmakers
IV. Dieback of plant parts Borers, scales, gallmakers
V. Presence of excrement, sooty
mold flocculence, froth, cast skins,
tents, pitch tubes, or other insect
product
Aphids, soft scales, mealybugs,
whitefly, adelgids, thrips, lace bugs,
spittlebugs, certain caterpillars, etc.

4.0 FINDINGS & UPDATES
SECTION 4: FINDINGS & UPDATES 107

4.1 Introductory Findings
Signal Hill Street Tree Policy from 2010 to 2022
was guided by three documents: the Street
Tree Policy, the 2010 Street Tree Master Plan
Update, and the 2011 Tree Ordinance. The next
section includes findings from analyzing these
policies, followed by the updated 2023 Street
Tree Policy. This 2023 Street Tree Master Plan
and the 2023 Street Tree Policy included in this
chapter will determine the city's street tree
policy from 2023 until the next Master Plan
update. Signal Hill's View Protection Policy,
previously cited in connection with street
tree pruning, is clearly intended to guide new
development, specifically buildings, not street
trees. In fact, trees are not mentioned at all in
the document. Therefore, analysis of the View
Policy is not included in the Street Tree Master
Plan.

4.1a Street Tree Policy Analysis
Signal Hill’s Street Tree Policy largely consists
of information from the Street Tree Ordinance,
though it does contain some original content
as well. The “whereas” clauses of the 2011
Street Tree Ordinance are conveyed as goals in
the Street Tree Policy, and include the following:
• Establish standards for the planting,
removal, replacement and maintenance of
all City Street trees.
• Create a sense of community, pride and
recognition to individual neighborhoods.
• Minimize maintenance costs and develop a
cost-effective tree planting program.

One piece of original content is the statement
that “The Director of Public Works shall develop
a street tree planting program for the existing
vacant tree sites incorporating the species
from the Street Tree Master Plan based on
conditions exclusive to that site, planting
standards, and surrounding environment.”
At the time this statement was written in
2010, 320 vacant tree sites existed in Signal
Hill. In the time between 2010 to 2022, the
number of vacant sites increased from 320
to over 1,000.

4.1b 2010 Street Tree Master Plan
Update Analysis
Much of the 2010 Master Plan text overlaps
with the Street Tree Policy and the Tree
Ordinance. The rest of the 2010 STMP contains
a tree palette.

The stated objectives of the 2010 Update to
the Street Tree Master Plan are as follows:

1. Evaluate the overall condition of the City’s
existing street tree inventory including
growth trends.

2. Inventory public right-of-way to identify
vacant tree sites and develop a tree
planting program based on planting
standards and site conditions.

3. Identify diseased, damaged, or unsuitable
trees and recommended replacement
trees.

4. Develop a cost-effective/ viable street tree
planting and replacement palette based
on environmentally-friendly trees species
suitable for unique conditions that may be
found at any given site.

Looking at these 2010 objectives, it appears
that Signal Hill completed objectives 1, 3, and

4. Objectives 1 and 3 were completed through
the WCA inventory of existing street trees.

Objective 4 was completed and included as
Appendix B “Street Tree Planting Schedule”,
which identifies the existing primary street tree
species on each block of the city, as well as
recommended replacement species for each
block. Objective 2 was partially completed
through the WCA inventory of vacant sites.

The part of objective 2 left incomplete is
development of a tree planting program.

View Protection Policy
As mentioned previously, the View Protection
Policy does not actually pertain to street trees,
but since there is confusion among the public
on this matter, the policy should be amended to
include exceptions for trees.
108 SIGNAL HILL STREET TREE MASTER PLAN
Several city policies regarding warrant updating,
with the following recommendations:

1. Add language to the City’s View Protection
Policy to clarify that the policy does not apply
to city managed trees, and that the city
does not prune or remove trees for reasons
relating to view enhancement requested by
residents. This language can then also be
included in the City’s Street Tree Policy.

2. Identify areas for prioritizing new tree
plantings for 5-year time period.

3. Create a budget for street tree planting and
maintenance, contingent on grant and other
funding.

4. Establish an Adopt-a-Tree Program,
contingent on staff availability to coordinate
the program.

Other policy changes may also aid the city in
improving its street tree numbers and health,
including these recommendations:

1. Create initiatives to plant street trees
in vacant sites proactively and without
requiring property owners to pay for the
installation.
a. Require that adjacent property owners’
consent to watering the tree throughout the
life of the tree.
b. Consider providing a watering bag with
each installed tree.
c. Provide the vacant tree well site list

4.2 Street Tree Policy
Recommendations
Street trees in Signal Hill. Photo: G. Castriotta
SECTION 4: FINDINGS & UPDATES 109
to the public, along with a tree request/
watering agreement form available on
the City’s website, which could facilitate
prioritization of tree planting locations in
residential neighborhoods.

2. Establish criteria for prioritizing new tree
plantings, such as:
a. Vacant sites with available water source
b. Submitted tree installation requests from
adjacent property owners that consent to
watering the tree
c. Replacing hazardous trees and trees
damaging public property

3. Plant trees in all areas of the city, and select
appropriate species to achieve the city’s
goals. Protect and preserve all desirable
trees, wherever they are located.

Encourage new tree planting on public
property and the cultivation of a flourishing
urban forest with an emphasis on native and
drought tolerant species.

4. Establish policy for street tree removal that
requires in-kind replacement within specified
timeframe.

5. Update the Street Tree Policy to reflect the
spacing requirements included later in this
chapter, and adopt the 2023 Street Tree
Policy.

6. Identify heritage trees for preservation.

7. Establish guidelines for root removals to be
evaluated by a certified arborist.

The following changes are recommended for the
Planting Guidelines:
• The requirement that trees be planted at
least 20 feet from bus stops should be
amended. Trees should be planted closer
to bus stops to provide shade for those
waiting.
• Minimum spacing requirements of 30 feet
between trees should be changed to allow
for closer planting of smaller species.
• Minimum tree well size should raised to 6'
long x 4' wide by 3' deep for all new street
tree sites. Older sites should be enlarged as
trees are replaced.

Development and Trees
Current City ordinances require the inclusion of
trees on development site plans along with a
notation of whether these trees will be retained
or destroyed; however, the ordinance does not
include any content regarding circumstances
by which tree removal would be approved or
denied, protection standards for retained trees,
and replacement requirements for removed
trees. This kind of content would be helpful
to maintaining and expanding the existing
stocking level of the street tree inventory, as
well as the maintenance and expansion of tree
canopy across the entire City. Additionally,
creating specific design requirements,
including the number of new street trees per
square foot, as well as irrigation requirements
and recommendation of modular paving
systems, would greatly improve the aesthetics
and environmental quality of new projects.

More detailed information on design guidelines
for new development is included in Section 2:

Design & Management Plan.

Google Earth
New development in Signal Hill should require new trees. 110 SIGNAL HILL STREET TREE MASTER PLAN

4.3 Tree Planting Program
Above all else, a review of Signal Hill’s 2011 Street Tree Ordinance, 2010 Street Tree Policy, 2010 Street Tree Master Plan, inventory data from Arbor Access, field observations, as well as interviews with city staff, indicate that creating and implementing a tree planting program to increase the stocking level above the current 74 percent is the most important goal for the updated Street Tree Master Plan. In the last 24 years (from June 1998 to June 2022) 1,224 street trees were removed, and few have been replaced. As this document emphasizes throughout, planting new street trees would provide great benefits to the city of Signal Hill. The following section outlines a path toward creating and implementing a street tree planting program.

4.3a Tree Planting Goals
The proposed goals of Signal Hill’s street tree
planting program are:

1. Increase the street tree stocking level from
its current level (74 percent in 2022) to 100
percent by 2033 by:
a. Planting trees in all vacant street tree
sites
b. Planting a replacement tree whenever a
street tree is removed, contingent on budget
c. Removing sites from the vacant sites
list that do not adequately accommodate
new trees and replacing with a new, more
appropriate site

2. Increase the resilience of the street tree
population by:
a. Increasing family, genus, and species
diversity
b. Bring the street tree population into
compliance with the 30-20-10 rule by not
planting Chinese elm (Ulmus parvifolia) trees.
c. Planting more drought tolerant, climateready tree species

3. Decrease future maintenance costs,
infrastructure conflicts, and public
complaints by:
a. Choosing appropriate species given site
constraints
b. Planting small or medium stature trees in
areas with view complaints involving street
trees
Table 21 Budget to Plant 1000 Trees in 5 years
Fiscal Year 22/23 23/24 24/25 25/26 26/27 27/28
Tree Trimming
Contract
Service1 $176,105 $180,508 $185,020 $189,646 $194,387 $199,247 Part time City
Maintenance
Staff time or
Contractor2 $43,000 $43,860 $44,737 $45,632 $46,545
Additional
Arborist
Services3 $18,000 $8,000 $8,000 $8,000 $8,000 $8,000
Additional
Trees 4 $150,000 $153,750 $157,594 $161,534 $165,572
Water Bags
(Irrigation)4 $5,000 $5,638 $6,356 $7,167 $8,080
Contingency $19,325 $19,813 $20,317 $20,836 $21,372
Total $194,105.00 $405,833.01 $416,081.21 $426,649.71 $437,555.17 $448,815.80 Notes
1 Regular tree maintenance contract
2 Part time maintenance staff or contractor to water and care for new trees. Must have Arborist back ground. 3 Additional arborist services cost will go down due to additional staff 4 CCLB's average cost for plant placement including equipment and delivery. 5 $20 water bag cost + 2.5 % material cost increase + 10% replacement cost SECTION 4: FINDINGS & UPDATES 111

4.3b Methods
The Signal Hill street tree planting program will
generally include:
• Planning/ coordinating
• Tree planting
• Establishment watering
The planning/ coordinating aspect of the
program can best be accomplished by one of
the following:
• A contracted consultant
• A city employee
The tree planting aspect of the program can be
best accomplished by one of the following:
• A contracted consultant leading volunteers
with support from city staff and equipment
• A local tree-planting non-profit leading
volunteers using their equipment
• A tree service contractor using their
equipment
• City employees using city equipment
The establishment watering aspect of the
program can be best accomplished by one of
the following:
• A local non-profit partner using their
equipment
• A tree service contractor using their
equipment
• City employees using city equipment

4.3c Funding
Of the methods listed above, most would require
identification of additional resources. If city
employees are to be utilized in planning, planting,
or watering, existing staff capacity would need
to be expanded. If city equipment is to be used in
planting or watering, additional equipment would
need to be acquired. If a consultant is used in
planning or in planting with volunteers, funding
would be needed. If a contractor is used for
planting or watering, funding would be needed.

The option of partnering with a local non-profit
for planting or watering may or may not require
additional funding. An approximate budget for
reaching these planting goals without the help of
a grant or partner organization is included in Table
21 on the previous page.

Among the various ways to acquire resources for a
street tree planting program, applying for grants is
one common way. Possible grant sources include
• CAL FIRE: Urban and Community Forestry Grant
Program
• California Natural Resources Agency: Urban
Greening Grant Program
• Port of Long Beach: Community Grants
Program
• Arbor Day Foundation: Grants
• Tree People: Community Tree-Planting
Initiatives
In light of all the options described above for
planning and implementing a tree planting
program, perhaps the simplest one is to hire
a consultant with expertise in urban forestry
and grant writing to lead the City through the
CAL FIRE Urban Forestry grant application.

The application can include funding for hiring
a consultant to assign the best species to
each vacant site, select and reserve trees at
nurseries, and arrange for tree deliveries. The
funding can also cover the expenses for WCA
to install the trees and perform establishment
watering.

Applications for this grant program happen on
an annual basis. CAL FIRE’s estimated timeline
for this cycle is that concept proposals will
be accepted for a one-month window at the
beginning of 2023. For concept proposals
that are invited to submit a full application,
the full application will be due in April 2023.

Grant awards are expected to be announced in
May or June of 2023, with grant-funded work
beginning around July 2023. Awarded grants are
active for three years (until March 2026). Grant
awards range from $150,000 to $1.5 Million.
112 SIGNAL HILL STREET TREE MASTER PLAN

4.3d Phasing Plan
While it may be possible to plant trees in
all 1,019 vacant sites in one year, it is not
preferable. Planting trees consistently over
time leads to a street tree population that is
more resilient because it possesses trees of
various ages. Phased planting can also spread
the planting and maintenance costs evenly
across years as opposed to causing acute
spikes in expense.

One way to approach phased street tree
planting in Signal Hill would be to spend six
months to one year planning, and then begin
planting 200 trees per year for five years. While
this plan would fill in all vacant planting sites in
five years, it does not address replanting of the
average of 50 trees street trees that are likely
to be removed over the course of the planting
project. To address this, the planting plan could
aim for 250 trees per year over five years, or
the replacement of future removed trees could
be accomplished through a different plan or
method.

It will make sense to develop a prioritization
system for the existing vacant sites.

Logistically, it often makes sense prioritize
clusters of vacant sites, as planting and
watering will be more efficient for clustered
sites. Depending on the funding for
establishment watering, it may make sense to
prioritize the planting of vacant sites where the
adjacent resident has expressed a willingness
to perform the establishment watering.

Planting trees in areas of greater need, i.e.
where there is a current gap in the street tree
canopy, also makes good sense, and can help
to close the shade equity gap.

Year 1 Year 5
Time
Figure 4.3.1: Phasing Plan. The street tree canopy will grow dramatically if the city plants 250 new trees annually over 5 years.

SECTION 4: FINDINGS & UPDATES 113

4.4 Tree Maintenance
Program

4.4a Maintenance Goals
The proposed goals of Signal Hill’s street tree
maintenance program are as follows:

1. Ensure the highest quality pruning possible
by stipulating that:
a. All contract specifications should require
that tree care operations adhere to the
ANSI Z133 Safety Requirements, ANSI A300
Standards for Tree Care Operations, and the
ISA Best Management Practices (BMPs)
b. All contract specifications should require
that tree care operations adhere to The
Federal Migratory Bird Treaty Act (MBTA), the
Federal Endangered Species Act, and the
California Fish and Game Code, Section 3503.
c. An independent tree consultant should
review the work of contract pruning crews on
a weekly or monthly basis during grid pruning
cycle.
d. The different pruning levels offered by the
pruning contractor to specific species and
specific contexts throughout the city should
be implemented.

2. Create a pest monitoring protocol.
a. Trees at risk of known pests should
be monitored at least annually for pest
presence.

3. Create a tree risk assessment protocol
a. In cases where a city employee assesses
a reported tree issue and a course of action
is not clear, call in a consulting arborist to
perform a Level 2 Tree Risk Assessment.
b. Create a city policy on the level of risk the
city is willing to tolerate for street trees.
c. Many cities retain trees with a low or
moderate risk rating. For trees with a high
or extreme risk rating, mitigation actions
are utilized to reduce risk to an acceptable
rating. If the risk cannot be lowered to an
acceptable level (low or moderate), then the
tree is removed and replaced.

Tree Data
Through analysis of the Arbor Access data, and
through field checks, it was found that the Arbor
Access is missing data, has inaccurate data,
and exhibits data inconsistencies. The nature
of these data issues suggests that the issues
have arisen though data management practices
over time as opposed to having arisen during
the original inventory of street trees. Help the
contractor improve tree data completeness,
accuracy, and consistency by:

1. Hiring an independent tree consultant to
update the entire tree inventory every 10
years, starting in 2023.

2. Tasking WCA with correcting the missing and
inconsistent data outlined in the WCA Data
Report.

3. Ensuring that future tree care contracts
require the contractor to update all tree
data fields for each tree whenever pruning,
removing, planting, or otherwise working
with a street tree.

Street tree maintenance. Photo: City of Chino Hills
114 SIGNAL HILL STREET TREE MASTER PLAN
Current street tree canopy in Signal Hill. Photo: G. Castriotta

4.4c Community Forest Master Plan
Beyond the Street Tree Master Plan, a
Community Forest Master Plan (CFMP) is
warranted. A CFMP includes the STMP, and goes
beyond to address tree statistics and goals
for other city trees (trees in parks and at city
facilities) as well as trees that are not city
owner or managed, such as trees on industrial,

4.4b Track Progress
Tracking of progress makes sense on an annual
cycle as well as on a decade cycle.

For the annual cycle, going over all the above
goals for tree planting, tree maintenance,
tree data, and tree ordinance/ policy makes
sense. Additionally, a “Street Tree Report Card”
can be published annually with the following
information:

Continuing the practices of updating the Street
Tree Master Plan every 10 years makes sense.

When updating the STMP, the total progress on
goals can be assessed, and revised goals can
be created.
commercial, state, federal, educational,
cemetery, and residential property throughout
Signal Hill. Creating a Community Forest Master
Plan could also help the city to develop a larger
budget for tree planting and maintenance.

Such a plan can bring together stakeholders to
generate ways to encourage tree canopy health
and expansion throughout the entire City.

Street Tree Numbers
Live Trees . . . . . . . . . . . . . . . . . . . . . . . . 3,183 Trees Planted . . . . . . . . . . . . . . . . . . . . . . 324 Species Diversity
Number of Species . . . . . . . . . . . . . . . . . . 98 Prevalence of Top Ten Species . . . . . . . . . 42%
Species Exceeding 10% . . . . . . . . . . . . . . . 0
Vacancy Rates
Vacant Sites . . . . . . . . . . . . . . . . . . . . . . . 695 Stocking Level . . . . . . . . . . . . . . . . . . . . . 82%

REPORT CARD
CITY MANAGED STREET TREES · 2024
Figure 4.4.1: Street Tree Report Card
SECTION 4: FINDINGS & UPDATES 115

7. Street trees shall be centered in the parkway between the sidewalk and curb unless near a bus stop.

8. Street tree well sizes should be a minimum of 4 x 6 x 3 ft. deep, with 6 x 6 or larger recommended. Tree wells with an opening of less than 8.3-square-feet (2.5 x 2.5) will support only small trees to maturity or medium-sized species for 10 to 15 years. Tree wells with an opening of 48-square-feet (6 x 8) can support large trees to maturity. Narrow parkways can be utilized by allowing the lateral spread of tree roots (e.g. 2.5 x 8 ft instead of 2.5 by 4 ft dimension for the tree well). Refer to the Street Tree Palette of the Street Tree Master Plan when determining species size and appropriate planting area. Use of root barriers will help prevent root damage and allow for a wider variety of species.

9. As a best practice measure, street trees should be situated to provide 4 feet of sidewalk clearance to allow for passage of wheelchairs, with a minimum of 30" where preexisting conditions prevent greater clearance from being provided, thus meeting ADA requirements.

10. Locate trees to minimize conflict with overhead utilities. Where overhead utilities exist, plant only small trees (refer to the Street Tree Palette of the Street Tree Master Plan when determining species size) that will not reach the height of the wires.

12.05.040 New Street Tree Planting
C. New street tree placement. Features that may be unique to an individual street parkway will be taken into consideration by the Director of Public Works when placing a new street tree. These include width of parkway, width of sidewalk, existence of sidewalk, utility poles, street lights, bus stops, traffic signs, ADA accessibility, utility boxes, and fire hydrants. Therefore, the following planting guidelines must be followed by the Director of Public Works to optimize street tree planting opportunities.

1. Tree species must be listed in the Street Master Plan Street Tree Palette.

2. Street trees shall have the following approximate spacing range, based on mature plant sizes (refer to the Street Tree Palette of the Street Tree Master Plan when determining species size):

Large trees: 30 to 40 feet apart
Medium trees: 20 to 30 feet apart
Small trees: 15 to 20 feet apart

3. Street trees shall be placed according to the above range regarding proximity to street lights and power poles. Trees should be placed away from the curb near bus stops to provide shade at the stop without interference to the bus. Trees should be planted 5-15' from the bus shelter, depending on species size.

4. Street trees shall be placed a minimum of 15 feet from the start of a street curb return.

5. Street trees shall be placed a minimum of 10 feet from a fire hydrant or driveway approach where possible.

6. Trees should be placed at least 5 feet from utility meters. Size and root invasiveness (refer to the Street Tree Palette of the Street Tree Master Plan when determining species size and root invasiveness) must be considered when planting near meters, drains, and underground utilities.

4.5 Tree Ordinance Update
116 SIGNAL HILL STREET TREE MASTER PLAN
long-term health of the new tree. The design considered factors such as drought-tolerance, species origin, size, branch strength, root damage potential, and aesthetics. The Street Tree Master Plan should be updated every five years and should include species name, mature height and width, recommended planting dimensions, water needs, branch strength, and utility friendliness.

Objectives
• Continue a comprehensive street tree maintenance program • Inventory public right of way to identify vacant tree sites • Provide a palette of environmentally-friendly tree species suitable for the current environment
• Include species selection criteria based on species characteristics and site conditions
• Develop a cost-effective, viable street tree planting and replacement program
• Update the Street Tree Master Plan every five years
Street Tree Inventory
The inventory should evaluate number, spacing, site condition, and tree health. A summary of the 2023 Street Tree Inventory indicates that 80% of the City street trees are in good condition, 14% are fair, and 5% are poor. The city should evaluate street tree inventory to eliminate trees species that did not meet expectations. As the city's urban forest matures, the originally-selected tree species may not necessarily be compatible with its current environment. The tree may have damaged adjacent hardscapes, outgrown its space or require excessive maintenance. New species should be identified that will thrive in the problem sites.

Introduction
Street trees, an integral part of the urban forest, are an important part of the attraction and character of Signal Hill's streets and neighborhoods, and provide many benefits to the community. Trees increase the beauty of neighborhoods and shelter homes from the hot summer sun or cold winter winds,and, as a result, lower cooling and heating bills. Trees also reduce erosion, buffer noise, reduce air pollution, and increase property values. The city maintains 2,859 live street trees for the benefit of the community. In fact, there are 88 different species and, collectively, the street trees have an estimated replacement value of $15.7 million dollars.

These trees sequester 1,674 tons of carbon, which is an economic value of $285,000. They help to capture and clean an estimated 35,000 cubic feet of stormwater runoff. Signal Hill's 2023 Street Tree Policy covers street trees only; the policy is not intended to be applied to trees located in city parks or on private property including private streets and property owned and maintained by homeowners associations.

Goals
• Fill vacant tree sites.
• Provide for the long-term health and prosperity of the city's street tree canopy by ensuring the right tree is planted in the right place. • Establish a high standard of maintenance and a sustainable care regimen for the city's street trees.

Street Tree Master Plan
The Street Tree Master Plan serves to establish a cohesive tree planting program with an appropriate diversity of tree species, designed to maximize the health of the street tree canopy by providing a palette and planting guidelines. These guidelines ensure that each new street tree's characteristics are appropriate to its site. The guidelines should also help minimize conflicts with utilities and sidewalks, and maximize the

4.6 Updated 2023 Street Tree Policy
SECTION 4: FINDINGS & UPDATES 117
interference to the bus. Trees should be planted 5-15' from the bus shelter, depending on species size.

4. Street trees shall be placed a minimum of 15 feet from the start of a street curb return.

5. Street trees shall be placed a minimum of 10 feet from a fire hydrant or driveway approach where possible.

6. Trees should be placed at least 5 feet from utility meters. Size and root invasiveness (refer to the Street Tree Palette of the Street Tree Master Plan when determining species size and root invasiveness) must be considered when planting near meters, drains, and underground utilities.

7. Street trees shall be centered in the parkway between the sidewalk and curb unless near a bus stop.

8. Street tree well sizes should be a minimum of 4 x 6 x 3 ft. deep, with 6 x 6 or larger recommended. Tree wells with an opening of less than

8.3-square-feet (2.5 x 2.5) will support only small trees to maturity or medium-sized species for 10 to 15 years. Tree wells with an opening of 48-square-feet (6 x 8) can support large trees to maturity. Narrow parkways can be utilized by allowing the lateral spread of tree roots (e.g.

2.5 x 8 ft instead of 2.5 by 4 ft dimension for the tree well). Refer to the Street Tree Palette of the Street Tree Master Plan when determining species size and appropriate planting area. Use of root barriers will help prevent root damage and allow for a wider variety of species.

9. As a best practice measure, street trees should be situated to provide 4 feet of sidewalk clearance to allow for passage of wheelchairs, with a minimum of 30" where preexisting conditions prevent greater clearance from being provided, thus meeting ADA requirements.

10. Locate trees to minimize conflict with overhead utilities. Where overhead utilities exist, plant only small trees (refer to the Street Tree Palette of the Street Tree Master Plan when determining species size) that will not reach the height of the wires.

Street Tree Planting
The Director of Public works shall develop a street tree planting program for the existing vacant tree sites, incorporating the species from the Street Tree Master Plan based on conditions specific to that site, planting standards, and surrounding environment. The City will make every effort to replace the trees as the city budget allows and/or by obtaining grant funding. Under direction of the Public Works Director, the City Engineer shall develop a Standard Plan for planting street trees.

The Director of Public Works shall determine the location of new or replacement street trees. Signal Hill has many streets with different characteristics; hence, one size does not fit all. There are streets with no parkways, and others have parkways with varying widths. Similarly, sidewalks do not exist on some streets and vary in width on streets that have sidewalks. Other features that must be taken into consideration when placing trees are utility poles, street lights, bus stops, traffic signs, utility boxes, and fire hydrants. Heavy emphasis on ADA accessibility is another key factor in sizing and placing trees. Therefore, planting guidelines have been developed to optimize tree planting opportunities.

Guidelines for planting street trees:

1. Tree species must be listed in the Street Master Plan Street Tree Palette.

2. Street trees shall have the following approximate spacing range, based on mature plant sizes (refer to the Street Tree Palette of the Street Tree Master Plan when determining species size):

Large trees: 30 to 40 feet apart
Medium trees: 20 to 30 feet apart
Small trees: 15 to 20 feet apart

3. Street trees shall be placed according to the above range regarding proximity to street lights and power poles. Trees should be placed away from the curb near bus stops to provide shade at the stop without 118 SIGNAL HILL STREET TREE MASTER PLAN
• ADA Access/Utility/Sign Obstruction
• Severely damaging adjacent hardscape or utilities
• Street trees are NOT to be removed to protect a view.

Property owners are also responsible to report to the City any observed decline of the health of a street tree and/or other observations consistent with the criteria listed above regarding street trees adjacent to their properties. Upon receiving these reports the City will take the necessary actions including possible replacement of the street tree at no cost to the property owner. A property owner may request replacement or removal of a street tree adjacent to the property for reasons other than defined above. The entire cost to perform this work, including incidental cost, if ultimately approved, shall be the responsibility of the property owner.

The Director of Public Works may establish a procedure for an entire block approach, for the purpose of removing existing street trees that have outgrown their useful life and are considered high maintenance. The procedure would include replacement of the trees consistent with the Tree Policy and Street Tree Master Plan.

Enforcement
Under California Penal Code 594 (A) (1), it is unlawful for any person to damage or destroy any public or private tree.

Tree Maintenance
A healthy urban forest takes a community effort. Adjacent home owners and business owners shall be responsible for the watering of street trees along the frontage of their properties. Property or business owners and residents should report any damage or suspected diseased trees to the Public Works Department.

The City performs periodic trimming work for all the street trees. Signal Hill is divided into four maintenance areas. Street trees are trimmed by the city's landscape contractor on a regular schedule, two quadrants per year as the City budget allows. Trees are trimmed regularly to make sure the sidewalks and streets are clear of any safety hazards. The City may change to a species-based maintenance schedule should budget allow. Signal Hill strives to maintain city street trees in a healthy and nonhazardous condition through good arboricultural practices.

Supplemental trimming of city street trees will be considered and, if approved by the Director of Public Works, the requester shall pay the extra tree trimming cost. The City does not allow property owners, residents or gardeners to trim street trees or tree branches on city property or within the public right-of-way.

Street Tree Removal
The Department of Public Works will assess the overall condition of each street tree as part of the street tree trimming cycle. Should one of the following conditions be observed as part of this assessment, the City will remove and replace the street tree at no cost to the adjacent property owner:
• Dead/ Diseased/Severely Declining tree
• Poorly structured (potentially hazardous)
• Seedling or Volunteer growth (palms, pepper, etc)
SECTION 4: FINDINGS & UPDATES 119

5.0 COMMUNITY PARTICIPATION
& EDUCATION
SECTION 5: COMMUNITY PARTICIPATION & EDUCATION 121

5.1 Community Outreach
The City of Signal Hill included a community
outreach program as part of the Street Tree
Master Plan update process. The purpose of
the outreach program was to notify the public
of the project and provide education on the
issues involved, as well as to solicit input
from community members. It included public
notifications, pop-up events, a community
open house and a workshop, as well as an online
survey.

This section includes a description of the
methods of notification and engagement that
were used to meet the city’s outreach goals,
analysis of the outreach results, and a summary
of how the information collected was integrated
into the updated Street Tree Master Plan. Full
results are included in the appendices.

5.1a Community Outreach Objectives
• Engage a wide range of Signal Hill residents
• Involve existing landowners, tenants, and
other stakeholders
• Identify and translate community needs and
values into plan recommendations
• Educate stakeholders on the physical,
mental, ecological and economic benefits of
a healthy tree canopy
• Build consensus to solve complex issues
• Report outcomes back to the community

5.1b Community Outreach Methods
SWA helped the city's communications and GIS
specialists to create an engaging, interactive
website for the project. The website provided
information on outreach events as well as an
interactive map to explore the city's current
street trees. The link to the online survey was
posted on the website. The city also provided
updates and information on outreach events
through social media, via Facebook, Twitter,
and Instagram. Additionally, flyers were handed
out at events and posted at parks, libraries,
and plant nurseries to advertise outreach
events and the online survey.

Two outdoor pop-up events were used to
inform the public about the plan and to
advertise upcoming workshops as well as ways
to become involved. The first, at a Concert
in the Park on Wednesday, August, 10, 2022,
Inspecting the street tree map. Photo: G. Castriotta
122 SIGNAL HILL STREET TREE MASTER PLAN
October Pop-up. Photo: P. Masek
through Wednesday, January 4, 2023. 84 people
participated in the survey, with 57 completing
it. Complete survey results are included in this
document in Appendix 2. The final outreach
event will be the presentation of the completed
Street Tree Master Plan update to the public in
2023.

Key Findings
• Survey respondents recognize the value of
street trees in their community
• Residents would like to see more trees in
their city
• Planting more native and climate-adapted
trees is important
• Water use and aesthetics are key criteria
for tree selection
• Respondents do not value views over trees
alerted concertgoers to the existence of the
Street Tree Master Plan with posters, and
encouraged them to visit the website for
more information on the update process.

The second, at the Mayor's Fall Cleanup
Event in Raymond Arbor Park on the morning
of Saturday, October 22, 2022, encouraged
attendees to come to the workshop event the
following week. A Community Open House at the
Signal Hill Public Library on Thursday evening,
September 15, 2022 educated participants
on the current status of the update, how
Signal Hill's street trees compared to nearby
cities', and encouraged future participation in
the Street Tree Master Plan update process.

Participants in the workshop asked great
questions and demonstrated their investment
in the future of Signal Hill's urban forest.

On Thursday, October 27, a hybrid Community
Workshop both in-person at City Hall and
online via Zoom presented some aspects
of the Street Tree Master Plan update and
included a Mentimeter survey with live-updated
results. The survey was intended to engage the
audience by educating them on the importance
of Signal Hill's Street Trees, explaining the
update process, and soliciting feedback. A
modified version of that survey, included in
the following pages, was posted online on
Monday, October 31, 2022 and remained open
SECTION 5: COMMUNITY PARTICIPATION & EDUCATION 123

5.2 Survey Slides with Results
Yes
No
What is a
Street Tree
Master Plan?
34%
18%
48%
Zone 1
Zone 2
6%
Zone 3 Zone 4
Other
39% 30%
12% 13%
1 2
3 4
124 SIGNAL HILL STREET TREE MASTER PLAN
5 6
7 8
SECTION 5: COMMUNITY PARTICIPATION & EDUCATION 125
9 10
11 12
126 SIGNAL HILL STREET TREE MASTER PLAN
26 12 29
Flowering
Deciduous
Evergreen
39% 43%
18%
13 14
15 16
SECTION 5: COMMUNITY PARTICIPATION & EDUCATION 127
17 19 20
18 128 SIGNAL HILL STREET TREE MASTER PLAN
21 22
23 24
SECTION 5: COMMUNITY PARTICIPATION & EDUCATION 129
Native California Trees
Climate Ready Trees
Other
Trees that look similar to
Chinese Elms
28% 61%
8%
3%
Native trees. Jacaranda - love the
flowers and the color they
provide when they bloom.

I love our palm trees. They
represent being in Southern
California and being near the beach.

I love pepppercorn trees because they
smell great, are useful, and provide good
shade. We need more shade in Signal Hill!
Gingko! Beautiful
leaves, color in autumn,
irregular graceful shape.

Any trees and shrubs
native to California that
are drought resistant.

Desert willow. Drought
tolerant native with
colorful flowers.

Tree-lined residential streets
are beautiful. I would love to
see more in my neighborhood.

Sycamore. Oak.

HOAs can partner
with the city to
plant trees.

Jacaranda.

Crape myrtles are nonnative but pretty and
good for limited space.

Eucalyptus.

Maple tree. I love the shape
of the leaves and the bright
colors during autumn.

Eucalyptus. I love how they’re
very tall and majestic. The tree
bark looks light and smooth.

Willow.

Cedar.

Palo Blanco.

Elm. Acacia.
25 27 28
26 130 SIGNAL HILL STREET TREE MASTER PLAN
29 31
30 32
SECTION 5: COMMUNITY PARTICIPATION & EDUCATION 131
10 18 29
Yes
No
Unsure
63%
30%
7%
Red Push
Pistache
Mulga
Island
Oak 51%
32%
17%
33 35
34 132 SIGNAL HILL STREET TREE MASTER PLAN
with less enthusiasm than for the previous
statements [Slide 6], indicating that the city
will have to carefully consider its irrigation
methods when planting new street trees.

Respondents ranked "improving air quality /
decreasing pollution" as the most important
role of trees in Signal Hill, followed by "reducing
heat / providing shade" and "improving people's
physical and mental health." Providing habitat,
aesthetics, and improving water quality
followed, with increasing property values at the
bottom [Slide 8]. Planting trees strategically
to provide shade, especially planting larger
species with greater shade production and
pollution reduction benefits, should therefore
be prioritized.

Asked their preference of evergreen, deciduous,
or flowering trees, people preferred flowering
closely followed by evergreen, in line with
their values of shade and beauty [Slide 14].

Aesthetically, respondents strongly preferred
spreading tree forms, reinforcing the need for
more shade in Signal Hill [Slide 15]. Round and
weeping forms were also popular. When ranking
the importance of street tree planting factors,
water use was the first priority (8.3), followed
by root damage (8.2) and size (7.9) [Slide 17].

These answers are in line with the findings
of this Street Tree Master Plan that the city
should plant trees that will thrive in Southern
California's drought-prone environment, as
well as to plant trees carefully in the future to
avoid current issues such as trees interfering
with utilities. Notably, citizens ranked "view"
as a lower-priority factor when planting trees,
at 6.6 ranking only above foliage type (6.1)
and below growth rate (7.2), shape (7), and
litter (7) in addition to the previous factors.

When asked whether they would prefer a large
tree with an impacted view, a small tree with
a partial view, or no tree with an open view,
all respondents preferred a tree (large tree 9,
small tree 8) to no tree (0) [Slide 18]. While
this question was added to the survey later and
therefore has fewer respondents (17), it clearly
indicates a preference for trees over views,
despite frequent complaints by a small number
of citizens about trees blocking views. Finally,
while granting aesthetics a lower consideration
for street trees, respondents ranked it first
as a factor in selecting a tree in front of their
home, followed by shade provided, water use,
and cleanliness [Slide 34]. While anecdotally,
many residents expressed annoyance with tree
litter, especially from jacaranda trees, in the
survey they granted it less importance, and
several expressed a desire for jacarandas to be
further planted in the city [Slide 26].

Survey respondents also strongly support
Survey respondents mostly lived in the city,
but some worked or patronized businesses in
Signal Hill [Slide 1]. Only 4 had children who
attend school in the city. A large number (24)
were members of an HOA in the city, a factor
which indicates that cooperating with local
HOAs could help streamline the tree-planting
process. While respondents came from all
across the city, the largest number lived in
Zone 4, a more affluent part of Signal Hill which
already has the greatest canopy cover [Slide
2]. Because people took the survey on their
own initiative, answers may skew to those
already invested in Signal Hill's environmental
wellbeing or those who have a problem with a
tree in their neighborhood. Most people (48%)
were not aware that the city has a Street Tree
Master Plan, and 18% wondered what a Street
Tree Master Plan was [Slide 3]. The city will
need to continue to educate residents about
the existence and nature of the Street Tree
Master Plan, especially the 2023 update.

When asked why trees are important, people
stressed shade, air quality and environmental
benefits, and beauty [Slide 4]. Respondents
strongly agreed with the statements "I would
like to see more trees in Signal Hill" and "It is
important to see more trees in Signal Hill."
People generally agreed that they would water
a tree planted in front of their home, but

5.3 Analysis & Integration
SECTION 5: COMMUNITY PARTICIPATION & EDUCATION 133
increasing Signal Hill's tree canopy by filling
vacant street tree sites, with 97% expressing
approval [Slide 21]. Respondents preferred
an even mix of trees sizes to only small and
medium or all large trees [Slide 22]. When
asked what kind of trees should replace
overused species such as Chinese elm to
restore balance to the urban forest, most
respondents (61%) preferred native trees,
followed by Climate Ready Trees (28%) [Slide
25]. The updated street tree palette contains
many native species; planting these species
should be prioritized. Respondents also had
much to say about their favorite trees [Slide
26]; a word cloud version is included on Slide
26, while the full comments are included in
Appendix 2.

Given pictures of 8 different species of native
trees, respondents expressed a preference for
the Western Redbud (15 votes), Incense Cedar
(11 votes), and Blue Palo Verde (9 votes) [Slide
29]. These trees should be included in future
plantings. Respondents found the benefits of
native trees to all be very important, especially
their suitability to the local environment [Slide
30]. Of the three Climate Ready Trees shown
to survey takers, respondents expressed
a strong preference for Island Oak (51%), a
large, drought-resistant native California tree
[Slide 33]. This tree should be used whenever
possible given both its strong qualifications
and popularity.

The survey included slides intended to educate
survey-takers on street tree establishment
[Slide 5], Urban Heat Islands [Slides 9-10],
tree canopy [Slide 11], benefits of native plants
[Slide 28], and Climate Ready Trees [Slide 31].

They are included in the slides on the previous
pages. These elements should continue to
be emphasized as Signal Hill implements and
promotes its updated Street Tree Master Plan.

Many survey respondents (63%) indicated they
would participate in a tree planting program
[Slide 35]. The city should capitalize on this
factor and encourage participation in such a
program as much as possible. Respondents
appreciate street trees, especially for shade,
pollution reduction, and aesthetics. They value
trees over views, and wish to see more native
trees in their city. This updated Street Tree
Master Plan should help guide the city in their
endeavor to create a robust urban forest in
compliance with the desires of the residents of
Signal Hill.

A view from City Hall. Photo: M. Fratino
134 SIGNAL HILL STREET TREE MASTER PLAN

5.4 Creation of a Community
Forest Master Plan
Local business of all kinds, including large
corporations with local offices, benefit from
the community forest. A community full of
trees makes the city a more attractive place to
do business, helps attract and keep workers,
and reduces energy costs. Trees planted on
or near business sites have a positive impact
on the image of the business as well as the
city as a whole. Treelined commercial districts
draw more customers than treeless ones.

Corporate campuses with impressive groves to
relax in with clients or during lunch are far more
memorable than corporate landscapes of grass
berms and shrubs. Industrial sites are often
improved by the screening effects of trees.

Shade trees in parking lots and near buildings
can greatly reduce cooling costs. It should
be noted that the enhanced public image
resulting from the private sector’s involvement
in the community forest is also an effective
marketing strategy.

The type of involvement depends on the type
of business. Developers play a major role in the
community forest’s growth, of course, but so
can other businesses if given the opportunity
and inspiration. As with residents, interaction
may be between the City and individual
business people or groups of businesses. Such
groups can be particularly influential in the
expansion of the forest, especially when their
intent is to make commercial districts more
attractive and humane.

Institutions - schools, hospitals and libraries
offer many opportunities for the community
forest. Their grounds provide room to expand
the forest, and their strong connections to
the community create a natural interest in
the forest. Schools and libraries are especially
invaluable in their role as community teachers,
but will need city support and advice to fully
develop this function.

Organizations such as Scouting groups,
community volunteer groups, civic
organizations, and environmental groups can
be encouraged to play an active role in the
creation and maintenance of the forest. These
groups will assist with community education
as well as participating in the physical needs of
the forest. Outreach programs aimed at these
groups will ensure their ongoing interest and
participation.

The entire community benefits from an
extensive, healthy, well-designed forest,
beyond the limits of the street tree population.

If possible, it is recommended that Signal Hill
create such a comprehensive plan, involving
trees not only in streets but parks, businesses,
and residences. Even if the city simply
continues to implement and regularly update
the Street Tree Master Plan, an informed,
involved populace is essential. Each individual
tree requires proper care to thrive, while the
forest as a whole needs long-term planning
and support to assure its growth. Community
involvement is therefore integral to the life of
the forest.

5.4a Who to Involve in the Community
Residents of Signal Hill are perhaps most
emotionally affected by decisions regarding
the forest. Contact with residents can be on an
individual basis, as in city-initiated newsletters
delivered to all households, or through
groups such as homeowners’ associations or
neighborhood-improvement organizations.

The formation of such groups should be
encouraged, in order to help disseminate
information and enlist support for the forest.

Organizations also create social bonds that
help build community spirit.

SECTION 5: COMMUNITY PARTICIPATION & EDUCATION 135

5.4b How to Involve the Community
This section describes some of the many ways
to bring the community into the process of
creating and maintaining the forest, starting
with types of participation.

Selecting trees
Residents usually have a strong notion of
how their neighborhood should look and what
its character should be. In addition, having a
hand in the design process will result in a more
personal connection between residents and
their neighborhood, engendering greater pride
of place. Citizens should therefore be brought
into this process as much as possible to review
planting plans for their areas.

Planting trees.

While all work associated with the forest is
important, perhaps the most satisfying job is
planting trees. This is where people develop
emotional attachments and a lifelong interest
in the forest. The more individuals who
personally plant a tree in the city, the greater
the long term support for the forest. This axiom
is especially applicable to the children of Signal
Hill. Setting a goal of having each child plant a
tree ensures that the ideals of the community
forest will be carried into the next generation.

The beautiful walnut tree in Raymond Arbor Park is an important part of Signal Hill's Community Forest.

Photo: G. Castriotta
136 SIGNAL HILL STREET TREE MASTER PLAN
all eyes focused on the forest will increase
the ability of the forestry staff to engage in
preventive maintenance, possibly saving trees
in the early stages of ill-health and eliminating
potential accidents.

Funding tree planting or maintenance.

Providing the mechanism for citizens, including
businesses and institutions, to donate money
earmarked for this work is an important avenue
of participation, particularly for people with
time or physical constraints.

Providing land for expansion of the forest.

Landowners with room to spare can be brought
into the forestation process without sacrificing
property rights. The benefits of trees to the
community - and to the planet - provide
convincing reasons to join the effort.

Advising the city on forestry decisions.

As particular issues arise, the city may
consider forming ad hoc advisory committees
to provide a connection between the city
bureaucracy and citizens, as well as a way
for both sides to exchange information and
voice concerns. The city forestry staff cannot
be expected to handle every decision about
every tree in the forest without such help.

Encouraging citizen input will give weight to the
term “community forest.”Tree Board University
offers guidance in this area.

Educating others about the forest.

The community’s teachers, biologists,
naturalists, historians, artists, landscape
architects, and horticulturists all have a great
deal to offer toward this worthy endeavor.

Maintaining trees.

Residents already play a hand in the
maintenance of the neighborhood street
trees - many people at least water the tree
fronting their house, and some go beyond this
to include fertilizing, minor pruning and the like.

Providing residents with standards for care will
result in healthier trees. In addition, residents
as well as businesses should be alerted to signs
of poor tree health or maintenance. Having
Signal Hill's parks have beautiful trees worthy of a Community Forest Plan. Photo: G. Castriotta SECTION 5: COMMUNITY PARTICIPATION & EDUCATION 137
Ways for Residents to Participate
Encourage neighborhood tree associations to
ensure a close relationship between residents
and their part of the forest. Activities could
include planting parties and maintenance
workshops, as well as celebratory events, all
of which help build ties between neighbors.

A participatory process should be used when
city staff begin planning for tree plantings
or removals in a neighborhood. This process
might include community meetings, preference
surveys, or design charrettes. It is advisable to
seek the needs and preferences of residents in
the case of neighborhood parks as well.

Residents interested in planting trees
community-wide might form a nonprofit
organization based on San Francisco’s “Friends
of the Urban Forest” or Los Angeles’ “Tree
People.” However, while such groups can play
an invaluable role in the community forest,
they should not be expected to substitute for
city support and forestry resources. If such a
group is formed, and depending on the available
resources, the City should offer assistance and
legitimization by way of seed money, grantwriting assistance, technical advice, meeting space and staff assistance.

Getting the Participation of Business
Inform businesses of options for supporting the
forest. A pamphlet describing the benefits of trees
could be distributed to the business community.

Inform retail businesses of the decision-making
process regarding street trees. Involve those
interested in the process as much as possible.

Businesses with large reserves of land in Signal
Hill should be encouraged to join the growing ranks
of companies nationwide that are converting
portions of their holdings to wildlife habitat. Some
ways this can be done:
• Convert standard turf to native grasses, which
have a higher wildlife value (and require no
summer water).
• Create shrubby edges to allow hiding and
nesting places for wildlife.
• Include as many native species of plants as
possible.
• Include plants that provide sources of food
for a variety of creatures. A single oak, for
example, can support more than 300 species
of insects, which in turn support dozens of
species of birds. Acorns from oaks also feed a
wide variety of creatures.
• Set up nesting boxes for various birds (owls
and other raptors adjust particularly well to
these manmade homes). The local Audubon
Society is one source of information for the
specifics of this project.

The Role of Institutions
Schools offer perhaps the greatest opportunity
for participation in community forest programs.

Our youngest citizens are tomorrow’s
caretakers of the forest, so concentrating
outreach efforts on them will have important
long term benefits. The outdoor environment of
most American schools consists of equal parts
asphalt and grass, with a scattering of trees
(often in street-tree-like rows), some play or
recreation equipment, and lunch tables. This
type of schoolyard is usually a sterile place, not
conducive to outdoor learning or creative play.

The extension of the community forest into the
schoolyards of Signal Hill can help remedy this
situation.

There are many creative ways to bring the
community forest to the schools, such as:
• Plant groves of fruits, nuts, or hardwoods
to act as hands-on educational labs as
well as potential sources of revenue for the
schools. Such groves would be best suited
to high schools or colleges, where classes
in the life sciences, agriculture, community
forestry and woodworking could all have a
hand in care and planting.
• Involve students of all ages in tree planting,
particularly plantings at schools. Personal
involvement in the process will reduce the
likelihood of vandalism and damage due
138 SIGNAL HILL STREET TREE MASTER PLAN
to carelessness (a potential problem with
young children unschooled in the ways of
newly planted trees).
• Use the Master Plan in the classroom.

The subject is a natural for civics classes
as well as the sciences. Additionally,
the California Department of Education
provides resources for environmental
education curriculum. A wide variety of
topics are covered, including forestry and
fire protection.
• Sponsor a workshop bringing together city
staff and local teachers to brainstorm
other ways to bring the community forest
into the classroom.

Libraries are symbols of the community’s
commitment to lifelong learning. The library
should act as the prime repository for books
and publications on trees and community
forestry, since it is accessible to the entire
community.

Hospitals are the community’s place for
healing. As such, they are appropriate places to
represent the overall health of the community
as symbolized by the planting of trees. A grove
of trees with medicinal value would make an
appropriate “outdoor room” for patients,
visitors and staff to use. One quarter of
prescribed drugs in the U.S. pharmacopea
contain plant derivatives; examples of species
include Salix alba and the native Rhamnus
pershiana.

How Organizations Can Help
Environmental groups need no convincing
about the benefits of trees. Some tasks that
might be carried out with their help:
• Planting parking lots to reduce the heatisland effect in the city. • Establishing “Clean Air Groves.”
• Join the California ReLeaf network for
statewide support of community forestry
projects.
• Helping businesses convert company land
to wildlife habitat.

Street trees waiting to be planted. Photo: Our City Trees SECTION 5: COMMUNITY PARTICIPATION & EDUCATION 139
Spreading the Word
The City can instigate a number of programs
to increase community awareness of its forest
resource. These actions fall into three broad
categories: publicizing city policies (including
this Master Plan), soliciting community support
and enthusiasm, and educating people about
trees and the forest as a whole. This section
suggests ways to do this, organized in these
categories.

Publicizing City Policies
• Publicize the Master Plan on the City
website, in local newspapers (both online
and print), and flyers posted at local
nurseries.
• Invite citizens to a community forestry
open house, attended by all city staff
members involved in the forest’s creation
and care. This could be a special focus
during Public Works Week.
• Make the Master Plan easily available; keep
a digital file posted for public access on the
City website.
•
Soliciting Community Support
• Publish a pamphlet that illustrates the
steps a citizen needs to take to plant a
tree. Include horticultural basics as well as
bureaucratic steps. Include a reference to
the planting and maintenance information
found in this document. The pamphlet can
be posted digitally to the city’s website,
as well as distributed to homeowner’s
associations and other community
organizations. Printed copies can be made
available at libraries and other public
facilities.
• Support the Arbor/Earth Day celebration
in April. Use this event as a venue
for interaction between city staff,
environmental groups, and the general
community to build support for forestry
efforts.

Providing Education
• Produce pamphlets that give residents
guidance on tree planting and care.

Pamphlet topics could include: proper tree
pruning and reasons to not top trees, the
benefits of deep-watering street trees,
keeping a two-foot circle around the trunk
free of other plantings, and keeping a
minimum 4’ x 6’ planting area around street
trees if installing pavement near them.

These maintenance efforts will greatly
enhance the health of the city’s street
trees.
• Offer hands-on tree-care workshops, either
free or with fees going to support the
community forest.

Conclusion
The creation of a Community Forest Plan or
the future updates of the Street Tree Master
Plan are important opportunities to build public
awareness and appreciation of the community
forest. The undertaking of a comprehensive
community forestry program is an important
initiative for Signal Hill, and as such should
receive ample attention. The city should
continue to involve residents in future editions
of any tree plan.
140 SIGNAL HILL STREET TREE MASTER PLAN

APPENDIX
Date Voter I live in Signal Hill.

I work in Signal Hill.

I own a business in Signal Hill.

I patronize
businesses in Signal Hill.

I manage a property in Signal Hill.

I am a member of an HOA in Signal Hill.

My
children attend school in Signal Hill.

I am retired.

Which zone
do you live in?:

Did you know
Signal Hill has a Street Tree
Master Plan?:

Rate your opinion on the
following
statements:: I would water a street tree
planted in front of my
home.

Rate your opinion on the
following
statements:: I would like
to see
more
trees in Signal Hill.

Rate your opinion on the
following
statements:: It is important to plant
more native
California trees in Signal
Hill.
2022-10-24 1 Yes 4 5 4
2022-10-31 2 x x Other Yes
2022-11-01 3 x 3 Yes 2 5 5
2022-11-03 4 x Other Yes 4 5 5
2022-11-03 5 x 3 Yes 2 5 5
2022-11-05 6 x x x 1 Yes 5 5 5
2022-11-08 7 x x Other Yes 5 5 5
2022-11-08 8 x x x x 3 Yes 5 5 3
2022-11-08 9 x x 1 Yes 5 5 4
2022-11-08 10 x Other Yes 3 5 5
2022-11-11 11 x 3 Yes 4 5 3
2022-11-14 12 x 3 Yes 4 5 5
2022-11-14 13 x 3 No 4 5 5
2022-11-15 14 x
2022-11-15 15 x
2022-11-15 16 x x x 3 No 5 5 5
2022-11-15 17 x x 4 No 1 5 5
2022-11-15 18 x 1 No
2022-11-15 19 x 4 ? 3 4
2022-11-15 20 x x x 3 Yes 5 5 3
2022-11-15 21 x x
2022-11-15 22 x x x 4 Yes
2022-11-15 23 x x 4 ? 5 5
2022-11-15 24 x 4 No
Slide Referenced: 1 2 3 6
APPENDIX 141
Date Voter I live in Signal Hill.

I work in Signal Hill.

I own a business in Signal Hill.

I patronize
businesses in Signal Hill.

I manage a property in Signal Hill.

I am a member of an HOA in Signal Hill.

My
children attend school in Signal Hill.

I am retired.

Which zone
do you live in?:

Did you know
Signal Hill has a Street Tree
Master Plan?:

Rate your opinion on the
following
statements:: I would water a street tree
planted in front of my
home.

Rate your opinion on the
following
statements:: I would like
to see
more
trees in Signal Hill.

Rate your opinion on the
following
statements:: It is important to plant
more native
California trees in Signal
Hill.
2022-11-15 25 x 2 No 5 5 5
2022-11-15 26 x x x 3 ? 5 5 5
2022-11-15 27 x 3 No 5 5 5
2022-11-15 28 x 3 Yes
2022-11-15 29 x 4 No
2022-11-15 30 x 4 No
2022-11-15 31 x Other ? 4 5 5
2022-11-15 32 x x 4 No 3 4 3
2022-11-15 33 x x x 4 ? 4 5 5
2022-11-15 34 x x 4 ? 3 5 5
2022-11-15 35 x x x x 3 No 5 5 5
2022-11-15 36 x x x 3 Yes 5 5 5
2022-11-15 37 x x x x
2022-11-15 38 x x 3
2022-11-15 39 x x x x 4 Yes 4 4
2022-11-16 40 x x Other Yes 2 5 5
2022-11-16 41 x Other No
2022-11-17 42 x x 1 Yes 5 5 5
2022-11-17 43 x 1 Yes 5 5 5
2022-11-17 44 x x x 1 Yes 5 5 5
2022-11-17 45 x 2 Yes 5 5 5
2022-11-17 46 x x 4 No 5 5 5
2022-11-17 47 x x x 4 No 2 4 4
2022-11-17 48 x x x 4 No 4 4 5
Slide Referenced: 1 2 3 6
142 SIGNAL HILL STREET TREE MASTER PLAN
Date Voter I live in Signal Hill.

I work in Signal Hill.

I own a business in Signal Hill.

I patronize
businesses in Signal Hill.

I manage a property in Signal Hill.

I am a member of an HOA in Signal Hill.

My
children attend school in Signal Hill.

I am retired.

Which zone
do you live in?:

Did you know
Signal Hill has a Street Tree
Master Plan?:

Rate your opinion on the
following
statements:: I would water a street tree
planted in front of my
home.

Rate your opinion on the
following
statements:: I would like
to see
more
trees in Signal Hill.

Rate your opinion on the
following
statements:: It is important to plant
more native
California trees in Signal
Hill.
2022-11-17 49 x x 4 ? 1 5 5
2022-11-18 50 x x x x 3 Yes 5 5 5
2022-11-18 51 x 4 No
2022-11-18 52 x x x 4 No 5 5 5
2022-11-18 53 x x 2 No 5 5 5
2022-11-18 54 x x x 4 No 3 4 5
2022-11-18 55 x
2022-11-18 56 x x x 4 ? 5 5 5
2022-11-18 57 x 4 No 4 3 3
2022-11-20 58 x x x 4 No 1 3 2
2022-11-20 59 x x x
2022-11-20 60 3 Yes 3 5 2
2022-11-20 61 x x x 4 Yes 1 3 5
2022-11-20 62 x x x 1 Yes 5 5 5
2022-11-21 63 x x Yes 1 1 3
2022-11-21 64 x 4 No 5 5 5
2022-11-21 65 x 2 ? 5 5 5
2022-11-21 66 x x x x 4 Yes 1 1 3
2022-11-22 67 x x 3 ? 5 5 5
2022-11-23 68 x x x 4 No 5 5 4
2022-11-23 69 x x x x
2022-11-23 70 x 3 No 5 5 5
2022-11-23 71 x x x 1 No 5 5 5
2022-11-23 72 x 1 No 1 1 1
Slide Referenced: 1 2 3 6
APPENDIX 143
Date Voter I live in Signal Hill.

I work in Signal Hill.

I own a business in Signal Hill.

I patronize
businesses in Signal Hill.

I manage a property in Signal Hill.

I am a member of an HOA in Signal Hill.

My
children attend school in Signal Hill.

I am retired.

Which zone
do you live in?:

Did you know
Signal Hill has a Street Tree
Master Plan?:

Rate your opinion on the
following
statements:: I would water a street tree
planted in front of my
home.

Rate your opinion on the
following
statements:: I would like
to see
more
trees in Signal Hill.

Rate your opinion on the
following
statements:: It is important to plant
more native
California trees in Signal
Hill.
2022-11-23 73 x x 3 ? 5 5 5
2022-11-27 74 x x 3 No 5 5 5
2022-11-29 75 x Other No
2022-11-30 76 x x x 4 No 5 5 4
2022-11-30 77 x 2 No
2022-12-01 78 x 4 No 5 5 5
2022-12-01 79 x x 4 ? 1 5 2
2022-12-01 80 x 1 No 5 5 5
2022-12-01 81 x 1 No 5 5 5
2022-12-01 82 x x 3 ? 1 5 5
2022-12-01 83 x x 3 ? 5 5 5
2022-12-01 84 x 4 No
2022-12-01 85 x 3 ? 5 5 5
2022-12-01 86 x
2022-12-02 87 x x x x x 4 No 4 4 5
2022-12-03 88 x x 3 No 1 4 5
2022-12-08 89 x x x x 4 No 3 5 5
2022-12-08 90 x x 4 Yes 5 5 5
2022-12-09 91 x x Other No 1 5 5
2022-12-17 92 x x x 3 No 5 5 5
2022-12-22 93 x x
2022-12-31 94 x x x x
2023-01-03 95 x x Other Yes 4 4
2023-01-03 96 x 4 No
Slide Referenced: 1 2 3 6
144 SIGNAL HILL STREET TREE MASTER PLAN
Voter
1 2
3 4
5 6
7 8
9 10
11 12
13 14
15 16
17 18
19 20
21 22
23 24
Rate your opinion on the
following
statements:: There are
too
many trees
in Signal Hill.

Rank the importance
of the
different
ways trees help
Signal Hill. : Reducing
heat / providing shade
Rank the importance
of the
different
ways trees help
Signal Hill. : Improving
air quality
/ decreasing
pollution
Rank the importance
of the
different
ways trees help
Signal Hill. : Improving
water quality
/ capturing stormwater
Rank the importance
of the
different
ways trees help
Signal Hill. : Improving
people's physical and mental health
Rank the importance
of the
different
ways trees help
Signal Hill. : Increasing
property values /
helping
to
drive
economic
development
Rank the importance
of the
different
ways trees help
Signal Hill. : Creating
aesthetics / sense
of place
Rank the importance
of the
different
ways trees help
Signal Hill. : Providing
habitat / increasing
biodiversity
1 1 2 3 4 5 6 7
1 3 4 1 6 7 5 2
1 4 2 5 1 7 6 3
2 3 6 2 5 1 4 7
1 6 1 2 4 3 5
2 2 4 3 1
1 4 1 6 5 7 3 2
1 6 1 7 4 5 2 3
1 5 1 6 7 4 3 2
1 3 5 4 1 7 6 2
1 3 5 7 6 2 1 4
1 1 5 3 4 7 6 2
1 5 1 2 3 6 4
3 7 3 6 4 2 1 5
1 4 6 7 1 5 2 3
1 5 1 7 2 4 3 6
1 3 2 1
Slide Referenced: 6 8
APPENDIX 145
Voter
25 26
27 28
29 30
31 32
33 34
35 36
37 38
39 40
41 42
43 44
45 46
47 48
Rate your opinion on the
following
statements:: There are
too
many trees
in Signal Hill.

Rank the importance
of the
different
ways trees help
Signal Hill. : Reducing
heat / providing shade
Rank the importance
of the
different
ways trees help
Signal Hill. : Improving
air quality
/ decreasing
pollution
Rank the importance
of the
different
ways trees help
Signal Hill. : Improving
water quality
/ capturing stormwater
Rank the importance
of the
different
ways trees help
Signal Hill. : Improving
people's physical and mental health
Rank the importance
of the
different
ways trees help
Signal Hill. : Increasing
property values /
helping
to
drive
economic
development
Rank the importance
of the
different
ways trees help
Signal Hill. : Creating
aesthetics / sense
of place
Rank the importance
of the
different
ways trees help
Signal Hill. : Providing
habitat / increasing
biodiversity
1 2 1 3
3 5 1 2 6 7 3 4
1 2 1 4 3 7 5 6
1 2 4 6 3 7 5 1
1 5 3 1 2 4
1 2 1 5 3 7 4 6
1 5 1 7 2 4 3 6
1 6 2 4 5 3 1 7
1 6 1 7 3 2 5 4
1 4 2 1 3 7 5 6
1 2 1 3 4 6 7 5
1 4 5 7 6 3 1 2
1 2 3 6 1 7 5 4
1 1 3 6 4 7 5 2
1 1
1 5 1 3 4 7 6 2
1 1
1 1
Slide Referenced: 6 8
146 SIGNAL HILL STREET TREE MASTER PLAN
Voter
49 50
51 52
53 54
55 56
57 58
59 60
61 62
63 64
65 66
67 68
69 70
71 72
Rate your opinion on the
following
statements:: There are
too
many trees
in Signal Hill.

Rank the importance
of the
different
ways trees help
Signal Hill. : Reducing
heat / providing shade
Rank the importance
of the
different
ways trees help
Signal Hill. : Improving
air quality
/ decreasing
pollution
Rank the importance
of the
different
ways trees help
Signal Hill. : Improving
water quality
/ capturing stormwater
Rank the importance
of the
different
ways trees help
Signal Hill. : Improving
people's physical and mental health
Rank the importance
of the
different
ways trees help
Signal Hill. : Increasing
property values /
helping
to
drive
economic
development
Rank the importance
of the
different
ways trees help
Signal Hill. : Creating
aesthetics / sense
of place
Rank the importance
of the
different
ways trees help
Signal Hill. : Providing
habitat / increasing
biodiversity
1 3 2 1
1 6 4 7 3 2 1 5
1 2 1 5 6 7 3 4
1 5 3 2 4 7 6 1
1 2 4 3 5 1
1 4 1 3 2
2 2 1 4 6 7 5 3
1 1 2 3 5 6 4 7
1 4 3 6 5 2 1 7
1 2 1 3 6 4 7 5
1 1 5 2 4 6 7 3
5 5 2 6 3 7 1 4
1 2 3 5 6 4 7 1
1 1 3 4 2
3 1
1 7 2 4 5 1 3 6
1 1 2 3 4
1 5 6 7 3 1 2 4
1 2 1 5 4 7 6 3
1 4 7 2 3 5 1 6
Slide Referenced: 6 8
APPENDIX 147
Voter
73 74
75 76
77 78
79 80
81 82
83 84
85 86
87 88
89 90
91 92
93 94
95 96
Rate your opinion on the
following
statements:: There are
too
many trees
in Signal Hill.

Rank the importance
of the
different
ways trees help
Signal Hill. : Reducing
heat / providing shade
Rank the importance
of the
different
ways trees help
Signal Hill. : Improving
air quality
/ decreasing
pollution
Rank the importance
of the
different
ways trees help
Signal Hill. : Improving
water quality
/ capturing stormwater
Rank the importance
of the
different
ways trees help
Signal Hill. : Improving
people's physical and mental health
Rank the importance
of the
different
ways trees help
Signal Hill. : Increasing
property values /
helping
to
drive
economic
development
Rank the importance
of the
different
ways trees help
Signal Hill. : Creating
aesthetics / sense
of place
Rank the importance
of the
different
ways trees help
Signal Hill. : Providing
habitat / increasing
biodiversity
1 1 6 4 3 7 5 2
1 5 1 6 4 7 3 2
1 2 1 3
1 1
1 3 2 1 5 4 6 7
1 6 7 5 1 4 2 3
1 2 1 7 5 3 4 6
2 2 7 3 5 1 6 4
1 3 1 2 6 7 5 4
1 6 2 1 4 7 5 3
1 4 3 5 7 6 1 2
1 1 2 4 3 6 7 5
1 1 2 4 3 7 6 5
1 1 2 6 4 5 3 7
1 5 1 2 4 6 3
1 1 2 3 4 7 5 6
1 2 7 6 5 3 1 4
Slide Referenced: 6 8
148 SIGNAL HILL STREET TREE MASTER PLAN
Voter
1 2
3 4
5 6
7 8
9 10
11 12
13 14
15 16
17 18
19 20
21 22
23 24
Which of the
following
options do
NOT
have an effect on Urban Heat Islands?: