Ontario, CA Landscaping Rules: Weed Ordinances (2026)

Ontario's weed-control rules are codified at Ontario Municipal Code Chapter 6-9 (Weeds and Refuse Abatement), sections 6-9.01 through 6-9.15. Section 6-9.01 defines 'Weeds' broadly to include weeds that bear downy or wingy seeds, 'sagebrush, chaparral, and any other brush or weeds that attain such large growth as to become, when dry, a fire menace to adjacent property,' poison oak and poison ivy that menace public health, and 'dry grass, stubble, brush, litter, or other flammable material that endangers the public safety by creating a fire hazard.' Section 6-9.02(a) declares: 'It shall be unlawful, and it is hereby declared to constitute a public nuisance, for any property to be maintained in such a manner as to allow weeds, rubbish, refuse or dirt, or any combination thereof to exist thereon.' On finding a nuisance, the Director (the City Manager or designee) serves a Notice of Violation ordering abatement under Ontario Fire Department regulations, and any abatement of weeds must be done under a City-issued permit. Section 6-9.02(c) allows the Director to declare seasonal and recurrent nuisances, after which repeat occurrences on the same parcel in the same year may be handled by a simple post-card notice, and Section 6-9.03 authorizes preventive chemical control of recurrent weeds. The City's Weed & Refuse Abatement program implements this with a 6-inch brush limit and twice-yearly vacant-lot inspections.