TO: TREE COMMITTEE
FROM: JEREMY SWAN, COMMUNITY SERVICES DIRECTOR
DATE: APRIL 16, 2026
SUBJECT:
Title
URBAN FOREST UPDATE
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SUMMARY
The Community Services Department is charged with the maintenance and care of the urban forest, including all planting, trimming, removal, and, when necessary, treatment of all City trees. Currently, the City’s urban forest is comprised of over 24,230 trees of over 300 unique species, with an estimated value of over $96.8 million. Each year Community Services staff outlines a maintenance plan for the urban forest based on the Tree Policies and Guidelines Manual and best practices of the industry. As staff works through the annual work plan, any changes to the local and regional urban forest are noted, and adjustments to the annual work plan are made as needed. This report serves as an update on the urban forest condition and activities over the past year.
RECOMMENDATION
Recommended Action
Staff recommends the Tree Committee recommend that the Community and Human Services Commission receive and file this report.
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ALTERNATIVE TO RECOMMENDATION
In addition to the recommendation, there is the following alternative:
• Refer the matter back to staff for additional information.
FINANCIAL REVIEW
The staff cost to prepare this report is estimated at $950 and is included in the operating budget of the Community Services Department.
ANALYSIS
The Community Services Department is charged with the maintenance and care of the urban forest. Under the direction of the Community Services Director, the Community Services Manager oversees the day-to-day operations of urban forest maintenance. Staffing for urban forest maintenance consists of one full-time Arborist and one full-time Maintenance Craftsworker I. The City Arborist oversees maintenance activities, performs inspections, and plans for the future of the urban forest. Due to the magnitude of the urban forest, the City outsources urban forest maintenance activities, and the City Arborist works closely with the contractor to ensure that the urban forest is maintained to City standards. West Coast Arborists, Inc. (WCA) has been the City’s urban forest maintenance contractor for over 15 years.
CURRENT STATUS OF THE URBAN FOREST
As of April 2026, the urban forest consists of approximately 24,230 trees, with a total value of approximately $96.8 million. Tree value is based on size, location, and species rating.
Tree Count over Time
About ten years ago, the urban forest was home to approximately 27,000 trees. Tree removals were primarily determined by the budget, and trees were removed as funding allowed. This meant that many dead, diseased, or hazardous trees were left in the ground until removal funding was available. Tree planting was not mandatory, and funding was limited to 200 trees per year. Additionally, during this time, little outreach was conducted to encourage reforestation.
In 2014, the Liquidambar mitigation plan was approved to begin removing liquidambars that showed signs of Xylella. During this time, the trees faced several years of drought and water restrictions, which greatly affected the rate of removal. Mandatory replanting began in 2014. Although trees were planted at the rate they were removed, water restrictions led to property owners not watering newly planted trees. This in turn led to a higher failure rate of young trees.
During 2018-2021, the reforestation program was funded through grant funds, which increased the number of tree plantings and leveled removals versus plantings. In 2019, Invasive Shot Hole Borer was identified in the City, which led to increased removals of affected species. In 2020, during COVID restrictions, there was limited interest in tree plantings.
The significant decline in tree count since 2022 is due to windstorms in January 2022 and January 2025. In 2023 the number of tree plantings was greater than the number of trees removed, which helped to offset a portion of the decline.
Below is a chart showing the number of trees in the urban forest over the past 13 years:
As the urban forest becomes healthier and potentially high-risk trees are slowly removed, staff will increase reforestation outreach with a focus on planting “the right tree in the right place.” Outreach will continue on the proper watering of trees to educate residents on proper watering during the different weather conditions. Healthier trees lead to a healthier, more sustainable urban forest.
Tree Diversity
The types of trees in the urban forest greatly affect the benefits produced, maintenance activities, and the urban forest budget. Based on tree inventory data, Claremont’s urban forest contains over 300 unique species, the top ten species being:
Top 10 Species
Size and Age Distribution
An urban forest with a wide age range offers a continuous flow of benefits and allows for better planning of urban forest activities. A tree’s age is determined by its diameter at breast height (DBH), or 4.5’ from the base of the tree. Below is the City’s current DBH distribution compared to the ideal distribution according to the U.S. Forest Service:
Because the City’s urban forest age distribution is inconsistent with the ideal, the City should continue replacing trees annually to reach ideal age distribution.
Geographical Distribution
Utilizing a geographic grid system allows staff to plan and budget for routine tree maintenance activities, including trimming and removals. Additionally, grids show where reforestation efforts should be focused. There are five geographical grids. Below is an overview of the number of City trees in each grid:
The City strives to replant all trees that were removed during the prior year, provided they are viable planting sites; however, reforestation is a partnership between property owners and the City. The Claremont Municipal Code requires property owners to water City trees; therefore, if a property owner does not want a new tree, a tree will not be planted because it will likely not be cared for.
Avian Activity
During this reporting cycle, no nesting birds were reported. WCA staff will continue to inspect for nesting activity during maintenance practices. Should the crews come across signs of nesting, a notice will be posted, and no work will be done until there is no evidence of nesting.
Urban Forest Highlights
Liquidambar Mitigation Program
Approximately 12 years ago, liquidambars began showing signs of Xylella dieback. Xylella fastidiosa is a non-curable disease that affects a tree’s vascular system. The only cure and prevention of further infection is removal of infected trees. When the program began, there were approximately 2,500 liquidambars in the City; currently, there are approximately 890. In years past, reported liquidambar numbers only included Liquidambar styraciflua (American sweetgums), as they seemed to be the most impacted variety. However, in recent years we have noted that other varieties are showing signs of Xylella dieback. The approximately 890 liquidambars remaining in the City include Liquidambar formosana and Liquidambar styraciflua ‘Rotundiloba.’
Each year, the City conducts an assessment of all liquidambars in the City. From this assessment, staff determines which trees require removal. Trees that present 75 percent or greater dieback and trees with dieback in branches greater than 6” in diameter are recommended for removal. Depending on available funding, the threshold for removal is adjusted. Last year, 21 liquidambars were removed, compared to 18 liquidambars in 2024, 33 in 2023, and 45 in 2022. Although Xylella is still present in the City, it is not as prevalent as in years past. This is most likely due to increased watering and routine trimming. The healthier a tree is, the better its ability to fight off disease. Over the next few years, staff anticipates the impact of Xylella on liquidambars will continue to decrease, leading to fewer removals.
Invasive Shot Hole Borer
Invasive Shot Hole Borer (ISHB), once known as the Polyphagous Shot Hole Borer, posed a large threat to the City’s sycamore and oak tree population. ISHB is an aggressive beetle that bores into trees and introduces a fungus that causes fusarium dieback, much like Xylella, and presents as pinholes in the trunk of the tree. In 2019, the City treated a large population of sycamore and oak trees with an experimental treatment. This treatment did slow the spread of the insect and infection in the City, but some mature sycamores were still lost. Due to cost, the City did not continue with widespread treatment. ISHB activity is less prevalent than in previous years, likely due to increased watering and awareness; however, the City continues to monitor and treat as necessary. Fewer than five trees each year were removed due to ISHB in 2023 and 2022. There were no sycamores removed due to ISHB in 2024 or 2025.
Pine Bark Beetle
A new threat to the City’s urban forest is the Pine Bark Beetle, an aggressive and fast-moving insect that feeds on the cambium layer of a pine tree, causing the tree to die back rapidly. Pine Bark Beetle activity increases during warmer months. Treatment is available, but usually by the time symptoms appear, the tree is too far in decline. The best mitigation practice is to remove an infected tree immediately to prevent further spread. In 2023, the City removed seven pine trees due to the Pine Bark Beetle, one more than in the previous year. There were no pines removed due to the Pine Bark Beetle in 2024 or 2025.
Tree Policies and Guidelines Manual Update
In January 2025, the City Council approved an update to the Tree Policies and Guidelines Manual. Revisions focused on six goals and objectives. Over the past year, staff worked to implement the six goals and objectives included in the Manual update. Below are the goals and objectives, and progress in each goal area:
• Best Management Practices
o Staff now inspects all nursery stock prior to planting.
o Staff works with WCA on pruning expectations for mature trees.
o Staff spot-checks trees following trimming to be sure trimming meets City standards.
• Tree Maintenance and Wildlife Protections
o Goal is to complete tree trimming prior to nesting season.
o If nesting activity is evident, tree trimming is suspended until no activity is present.
• Maintaining the Tree Canopy
o Reforestation numbers are still slow to increase.
o Staff will work on community outreach, including increased advertising and contact with residents with vacant planting locations.
o Focus on “Right Tree, Right Place” planting.
• Removal Parameters
o To date, no non-emergency tree removals have occurred.
• Infrastructure Conflict Resolutions
o To date, no removals have met established criteria.
• Communication, Transparency, and Procedure
o Non-emergency tree removals have been posted bi-monthly.
Looking Ahead
The 2024-26 budget includes funding for a five-year grid trimming cycle. A five-year cycle is more in line with industry standards, will lead to a healthier urban forest, and will reduce City liability. More frequent trimming helps trees adjust to urban conditions, supports healthy growth, reduces damage during storms, and reduces risk of failure and decay. The fourth year of the new five-year grid trimming cycle is complete, and the benefits of the more frequent trimming cycle can be seen throughout the City. There are lower frequencies of downed trees and branches, and fewer visibility/line-of-sight issues.
As a means to ensure high-quality new trees, City staff will continue to inspect all nursery stock prior to planting. WCA brings nursery stock to the City Yard for inspection, and any stock that is not in accordance with City standards is rejected. WCA will return with new stock as needed until all nursery stock meets City standards.
In January 2025, the City Council approved the updated Tree Policies and Guidelines Manual. Revisions included a new notification procedure for non-emergency removals. Per the revised Manual, all non-emergency removals will be posted on the City’s website for a 15-day public objection period. Postings occur on the 1st and 16th of each month, given there are recommended non-emergency removals. The new procedures include an automatic notification process, open to anyone that opts in by signing up via the City website or email. Anyone who has opted in receives by email a notice that information has been posted on the website.
In March 2026, the City Council approved the 2026-28 City Council Priorities and Objectives. One of the objectives in support of the priority to “Preserve Our Natural, Cultural, and Historic Resources” states:
Ensure that the City’s Sustainable City Plan, Urban Forest Management Plan, General Plan, Municipal Code, Tree Policies and Guidelines Manual; internal policies/procedures; and staff/contractor qualifications and instructions are all consistent with best urban forest practices and with one another, and are effective in preserving and expanding our City’s Urban Forest, both public and private.
To that end, staff will begin reviewing the aforementioned documents with an eye toward consistency. This review and analysis will begin in summer 2026.
Take-Aways
This year, the City is on track to reach average rain fall totals; however, we are seeing a slight increase in young trees suffering from a lack of water. To help prevent development of drought stress symptoms, WCA is now adding mulch around the base of all newly planted trees to help retain water. Staff will continue to work with property owners on the importance of tree watering and to educate the community on the many benefits trees provide.
Healthy, well-maintained trees are better equipped than stressed and declining trees to fight off disease and infections. In addition, a healthy, well-maintained urban forest leads to fewer liability claims for property damaged by downed trees and branches. It is imperative that the City maintain a healthy urban forest, and as the City moves forward with urban forest maintenance, staff strives to maintain a quality urban forest with a greater focus on responsible planting, proper young tree care, and sensible preservation of the aging forest.
CEQA REVIEW
This item is not subject to environmental review under the California Environmental Quality Act (CEQA).
PUBLIC NOTICE PROCESS
The agenda and staff report for this item have been posted on the City website and distributed to interested parties. If you desire a copy, please contact the Community Services Department.
Submitted by: Prepared by:
Jeremy Swan Cari Dillman
Community Services Director Community Services Manager