Napa County, CA Landscaping Rules: Weed Ordinances (2026)

030 of the Napa County Code defines 'weeds' to include weeds that bear seeds of a downy or wingy nature; sagebrush, chaparral, and any other brush or weeds that attain such hard growth as to become, when dry, a fire hazard; weeds and grasses that are otherwise noxious; poison oak when growth conditions constitute a menace to public health; and dry grass, stubble, brush, litter, or other flammable plant material that endangers the public safety by creating a fire hazard. 'Combustible vegetation' is defined as material that in its natural state will readily ignite, burn, and transmit fire to any structure or other vegetation, including but not limited to dry grass, brush, weeds, dead or dying trees, litter, or other flammable vegetation.

060, the presence of such prohibited materials within the 100-foot defensible space around any structure, or on any undeveloped parcel one acre or less in size, is declared a nuisance subject to abatement by the property owner. The Napa County Defensible Space Guidelines (May 2021) further require, within Zone 0 (Ember Resistant Zone, 0-5 feet of the structure), the use of noncombustible landscaping materials and approved high-moisture-content annuals and perennials. 080 places responsibility on adjacent property owners when a structure is less than 100 feet from a property line and prohibited materials on the neighboring parcel present a fire hazard.

State law (California PRC Sec. 4291) applies the same defensible-space obligations within State Responsibility Areas. There is no county code section setting a specific maximum grass height in inches; the operative standard is whether the vegetation is dry, dead, or otherwise constitutes a fire hazard.