Arvada, CO Invasive Plant Rules: Prohibited Species (2026)

Section 18-484 of the Arvada City Code amends the International Property Maintenance Code's definition of 'noxious weed' to name seven species outright: Leafy Spurge, Canadian Thistle, Musk Thistle, Russian Knapweed, Diffuse Knapweed, Spotted Knapweed, and Purple Loosestrife. A plant also counts as noxious if it aggressively invades native plant communities or crops, poisons livestock, carries destructive insects or disease, or otherwise harms agricultural or natural ecosystem management. 4) makes the rule operative: all premises and exterior property must stay free of weeds or dead plant growth over 12 inches, and noxious weeds are prohibited altogether, with no height threshold.

Ownership does not shield a resident from liability; the ordinance names owners, agents, and any resident 'having charge of a property' as responsible parties. 2 separately bars ornamental grasses outside the A-1 and R-CE agricultural zoning districts, though small cultivated plots used as part of a landscaping plan are exempt. 3 requires the method used to minimize reseeding or reproduction, so mowing that scatters seed heads can itself trigger a follow-up violation. , enforced through the building inspection division's code compliance program rather than a separate weed board.