San Mateo County, CA Landscaping Rules: Tree Trimming (2026)
Key Facts
- Pruning permit trigger
- Cut >= 6 in diameter on Protected Indigenous Tree
- Circumference equivalent
- 19 inches
- Ordinance
- Chapter 8.400, Section 8.400.070
- Right-of-way trimming
- Public Works, safety only (no aesthetics)
- Pruning standard
- ANSI A300
Summary
In unincorporated San Mateo County, pruning a Protected Tree generally does not need a permit, but a Protected Tree Pruning Permit is required to prune a Protected Indigenous Tree where the cut removes a branch or trunk 6 inches in diameter (19 inches circumference) or larger. Trees in the County right-of-way are trimmed by Public Works for safety only.
4291. (a) A person who owns, leases, controls, operates, or maintains a building or structure in the state responsibility area shall at all times do all of the following: (1) (A) Maintain defensible space of 100 feet from each side and from the front and rear of the structure, but not beyond the property line, except as provided in subparagraph (B). The amount of fuel modification necessary shall consider the flammability of the structure as affected by building material, building standards, location, and type of vegetation. Fuels shall be maintained and spaced in a condition so that a wildfire would be unlikely to ignite the structure. This subparagraph does not apply to single specimens of
Full Breakdown
Under the County's Protected Tree Ordinance (Ordinance No. 400, adopted October 22, 2024), routine pruning is more lightly regulated than removal. 070). The same 6-inch pruning trigger applies in the specified Bayside Design Review Districts (Emerald Lake Hills, Oak Knoll Manor, Palomar Park, Devonshire). Topping is discouraged as a harmful practice. For trees within the public road right-of-way of the unincorporated districts, the Department of Public Works performs trimming for safety purposes only - site clearance near intersections, vehicle/pedestrian height clearance, and removal of hazards like broken or diseased limbs - and explicitly states it cannot trim trees for aesthetic reasons or with property-tax funds.
Private trees that overhang the right-of-way must meet the same clearance standards; the County will notify the owner and, if they decline, perform the trimming. Pruning should follow ANSI A300 standards.
Violations & Fines
Pruning a Protected Indigenous Tree beyond the 6-inch threshold without a Pruning Permit, or excessive pruning/topping that damages a Protected Tree, can be treated as a code violation. Unauthorized work in the County right-of-way may also require corrective action through Public Works.
Frequently Asked Questions
Do I need a permit to prune a protected tree on my property?
Will the County trim a street tree for me?
Sources & Official References
Other rules in San Mateo County
California rules heatmap·Compare San Mateo County to another location·View the California landscaping rules overview
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