San Mateo County, CA Landscaping Rules: Weed Ordinances (2026)
Key Facts
- Weed/grass max height
- 4 inches (mowed)
- Lots <= 1 acre
- Clear entire lot
- Lots > 1 acre
- 30-foot perimeter fire break
- Wetland buffer
- No mowing within 100 ft of wetland
- Disking
- Prohibited by County & Half Moon Bay
- Authority
- H&S Code 14875 et seq.; Gov Code 25845
Summary
Unincorporated San Mateo County abates hazardous fire vegetation through its fire districts under California Health & Safety Code 14875 et seq. and Government Code 25845. Programs such as Coastside Fire's require mowing weeds and grass to no taller than 4 inches; lots of one acre or less are cleared entirely, and larger lots need a 30-foot perimeter fire break.
5004. “Noxious weed” means any species of plant that is, or is liable to be, troublesome, aggressive, intrusive, detrimental, or destructive to agriculture, silviculture, or important native species, and difficult to control or eradicate, which the director, by regulation, designates to be a noxious weed. In determining whether or not a species shall be designated a noxious weed for the purposes of protecting silviculture or important native plant species, the director shall not make that designation if the designation will be detrimental to agriculture. (Amended by Stats. 1992, Ch. 556, Sec. 1. Effective January 1, 1993.) <input type="hidden" name="javax.faces.ViewState" id="j_id1:javax.fac
Full Breakdown
, Government Code 25845, and Penal Code 370 et seq. ' Combustible grass, weeds, trash and rubbish must be removed from vacant lots, yards, courtyards and parkways. ' To protect sensitive habitat, there is no mowing within a wetland or within a 100-foot buffer around a wetland, and fire breaks must stay at least 50 feet from riparian (streamside) vegetation. ' Defensible space under PRC 4291 (see Grass Height) overlaps these requirements for structures.
Violations & Fines
Owners who fail to abate after notice can have the vegetation cleared by the district/County, with the cost billed to the owner and, if unpaid, placed as a lien or special assessment on the property tax roll. Disking is prohibited as an abatement method.
Frequently Asked Questions
How short must I cut weeds on a vacant lot?
Can I disk my lot to clear weeds?
Sources & Official References
Other rules in San Mateo County
How San Mateo County compares: Cities with the Strictest Weed and Property Maintenance Rules·California rules heatmap·Compare San Mateo County to another location·View the California landscaping rules overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.