March 25, 2025
Suitability of AdopƟng and Retaining 61 Canary Island Pine Trees along Serrano Blvd, and 22 Canary Island Pine Trees along Cannon St.
Prepared by:
Micah Jean – City of Orange Tree Services Coordinator
ISA Board CerƟfied Master Arborist WE-9971BM
ISA Tree Risk Assessment Qualified | ISA CerƟfied Urban Forest Professional Prepared for:
Chris Cash – City of Orange Director of Public Works
Background:
In August 2023, I provided a summary report of condiƟons regarding the suitability of adopƟng trees within the Right of Way adjacent to Mabury Ranch HOA. The report primarily served as a broad overview to establish esƟmated iniƟal and future maintenance costs. Future liability concerns due to observable condiƟons was a determining factor in anƟcipated costs.
A thorough inspecƟon of condiƟons was performed in March, 2025. This document serves to provide addiƟonal informaƟon on the 61 Canary Island Pine trees along Serrano Blvd, the 22 Canary Island Pines on Cannon St, and my recommendaƟon to remove the 61 trees on Serrano Ave, if adopted as City responsibility. This document is not intended to provide every observaƟon or potenƟal factor of concern, relaƟng to current condiƟons, defects, and likely future liability of these trees.
Method:
To determine the likelihood of future liability issues, and compaƟbility as City trees: trees were assessed for species characterisƟcs, immediate hazard, tree structural integrity defects, site condiƟons, and observed current infrastructure damage.
Tree Species CharacterisƟcs:
Canary Island Pine is the largest pine species naƟve to the Old World, with recorded height and width of 196’ tall and 105” DBH.
Mature trees are commonly 80-120’tall, with trunk widths 35-50” DBH. Canopy widths are commonly 20-35’.
Specimens in the naƟve range are reported to live over 800 years. In California, anƟcipated longevity is 100-200 years.
On a Low / Moderate / High scale for root damage potenƟal, Canary Island Pine is rated as Moderate.
Canary Island Pine has a generally deep root system. PrevenƟng root related infrastructuredamage relies upon correct site suitability and placement.
1 PlanƟng Site CondiƟons:
On Serrano Ave:
52 trees are located within 11 planters, behind the sidewalk and abuƫng the private HOA wall.
Planters are 4’ wide, with some minor variance in width. Trees within planters are spaced an average of 17’ apart, with some outliers. Trees in planters were measured to be between 7” and 29” to the wall, and from 9” to 28” to the sidewalk.
9 trees are located east of the planters, with distances of up to 7’-9’ to HOA wall, and 26” to 68” to sidewalk.
On Cannon St:
22 trees are located behind the sidewalk, adjacent to an open trail. Trees are generally spaced between 17’ to 20’ apart. Trees measured between7’to 8’to HOA wall, and 30” to 45” to sidewalk (with 1 excepƟon).
CompeƟƟon with Private Trees:
Many trees were observed to be in current conflict with private property tree canopies, and other trees are anƟcipated to have future conflicts with private trees, as the trees mature. On Serrano Ave:
22 trees were observed to have canopies within 10’ of private trees. 11 trees were observed to be in contact with private trees. 23 tree trunks were observed to have less than 30’ proximity to private tree trunks.
On Cannon St:
8 trees were observed to have canopies within 10’ of private trees. 4 trees were observed to be in contact with private trees. 11 tree trunks were observed to have less than 30’ proximity to private tree trunks.
Tree CondiƟons:
On Serrano Ave:
Current tree size is generally small for the species, with DBH measurements between 5” and 20”. The majority of trees are approximately 8”-12” DBH. The 61 trees have the capacity to grow far larger than their current size. Defects in the main stem or branch structure were observed in many (15) trees. Of 15 trees with observed structural defects, 5 consƟtuted severe defects that currently warrant tree removal.
Of the 9 trees to the east and outside of the 4’ planters:
3 trees are sƟll staked, and staked improperly with a splint, which weakens trunk development. 2 addiƟonal trees were observed with poor structure.
4 trees have observable adjacent infrastructure damage. 1 tree trunk measured 9’ to light pole.
3 trees have insufficient distance to 1 or more adjacent Crape Myrtle trees. On Cannon St:
DBH measurements range from 10”-27”. The majority of trees are approximately 17”-20”. The 22 trees are anƟcipated to grow larger than their current size. 5 trees were improperly pruned to remove the majority of branches on the East facing side. 1 tree was impacted by an embedded 3”metal pole. No other substanƟal defects were observed.
2 Current Infrastructure Damage:
On Serrano Ave:
41/61 tree locaƟons observed to have current adjacent infrastructure damage. 27 locaƟons observed to have damage to public infrastructure. 28 locaƟons observed to have damage to adjacent private wall.
On Cannon St:
13/22 tree locaƟons observed to have current adjacent infrastructure damage. 8 locaƟons observed to have damage to public infrastructure. 7 locaƟons observed to have damage to adjacent private wall.
PotenƟal for Future Damage and Liability:
Proper planning for tree planƟng is essenƟal to have healthy, long lived trees that provide many benefits, while limiƟng liability over the lifeƟme of trees.
When determining suitable tree placement for a site, an important factor is the space available for canopy, trunk, and root growth. Considering soil volume is a necessary component of site suitability.
Trees require adequate oxygen-rich soil space for their roots, to anchor and provide the tree water and nutrients. When trees are surrounded by hardscape, their available root space isgreatly diminished and made more inhospitable due to soil compacƟon, and other factors. When trees are placed close together, this also reduces soil volume available per tree, and the trees compete for this space. These condiƟons can create adverse effects, such as: stunted growth, poor health, poor anchorage, abnormal or raised root crown (mounding of the soil around trees), suscepƟbility to spread of pests and disease, increased likelihood of root conflicts with infrastructure, and increased likelihood of tree failure.
Generally, a “good”soil volume for a large tree is 1000 cu. Ō. For reference, the County of San Diego requires 600 cu. Ō. for small trees, 1000 cu. Ō. for medium size trees, and 1500 cu. Ō. for large trees (County of San Diego BMP Design Manual, SecƟon K, pg 32). The City of Orange Master Street Tree Plan (1999) establishes 8’ x 8’ as a minimum planƟng area for the species. If the root zone is limited to an 8’ x 8’ square, the soil volume is esƟmated as 192 cu. Ō. On Serrano Ave:
52 trees within the 4’ planters do not meet the minimum requirement of an 8’ x 8’ square, and also do not have adequate soil volume. Trees within the 4’ planter are very likely to cause both public and private infrastructure damage. It is very likely that the future replacement of surrounding infrastructure would require the removal of trees.
On Cannon St:
22 trees have comparaƟvely far more soil volume, and root space. Trees are located further from the private wall, as well as sidewalk. Trees are inadequately spaced, and in too close proximity to private trees. Due to the current proximity of the privatewall and sidewalk, there is opportunity to follow the City standard operaƟng procedure for root miƟgaƟons. There is potenƟal for selecƟve root removal to allow for retenƟon of trees, at the Ɵme of potenƟal future sidewalk replacement.
Conclusion:
The Canary Island Pine trees of concern are generally not observed to be diseased, though there are a range of minor to major defects on some trees. Many trees have adjacent infrastructure damage present. Many trees have canopy conflicts with private trees. On Serrano Ave:
The mature size of the species is highly non-compaƟble with the proximity to the HOA wall, as well as the undersized planter where they reside. The current size of the pines is considered small/ immature for the species, and it is anƟcipated that they would grow much larger . A mature Canary Island Pine 3 has the potenƟal trunk size over 4’ in diameter,as wide as the enƟre planter . As trees mature, their trunk flare and root crown (the widening at the base of the tree, where the trunk connects to the roots) oŌen become more pronounced, which has a very high likelihood of damage to adjacent infrastructure when planted in inadequate space.
Due to the inadequate space, the likelihood of any root miƟgaƟons performed being successful without undermining the stability of the trees is unlikely. When making determinaƟons to the suitability of selecƟve root removal for root miƟgaƟons, proximity of cuts to the trunk is a major consideraƟon. It would be very likely that sidewalk replacement would result in observaƟons of root caused damage, and required root miƟgaƟons would result in the removal of trees.
It is very likely that 52 trees planted within the 4’ planter will present with future liability issues. The likelihood of future issues greatly exceeds the potenƟal liability of typical new City tree locaƟons, due to the combinaƟon of small planter size, proximity to private infrastructure, and species.
The 9 trees not located in 4’ planters are assessed to havecomparaƟvely lower likelihood of damage related to soil volume, and distance to the private wall. The 9 trees were observed to have defects, substanƟally inadequate spacing, and current adjacent infrastructure damage. 61/61 Canary Island Pine Trees located on Serrano Ave are recommended for removal, if adopted as City responsibility.
On Cannon St:
There is a comparaƟvely far greater space between infrastructure and trees, on Cannon St. Due to more available space, there is potenƟal to follow normal root assessment and miƟgaƟon procedures during infrastructure repair .
22/22 Canary Island Pine Trees located on Cannon St are recommended for retenƟon, if adopted as City responsibility.
4 Examples of Current Infrastructure Damage
28 tree locations observed to have current damage to adjacent private wall. 5 Examples of Current Infrastructure Damage
6 7
8 9
10 11
12 13