San Mateo County, CA Landscaping Rules: Tree Trimming (2026)

Under the County's Protected Tree Ordinance (Ordinance No. 4895, Chapter 8.400, adopted October 22, 2024), routine pruning is more lightly regulated than removal. A Protected Tree Pruning Permit is required for pruning of Protected Indigenous Trees 'where the cut would result in the removal of a branch or cutting of the trunk which is 6 inches in diameter (19 inches in circumference) or greater at the point of the cut' (Section 8.400.070). 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.