Ada County, ID Invasive Plant Rules: Prohibited Species (2026)

Chapter 8 of Title 5, adopted by Ordinance 741 on January 19, 2010, is built on Article 12, Section 2 of the Idaho Constitution and Idaho Code sections 31-714, 31-801, 22-2405, and 22-2409. Section 5-8-3 flatly declares it unlawful for any landowner to knowingly maintain noxious weeds on their land within the county. Section 5-8-5 defines a "noxious weed" as any plant with the potential to injure public health, crops, livestock, land, or other property, and which is designated as noxious by the director of the Idaho Department of Agriculture, meaning the operative species list is set at the state level rather than by county ordinance.

The County Weed Superintendent, employed by the Board of Ada County Commissioners, is charged with detecting and treating designated species. Enforcement under section 5-8-6 begins each year with a general public notice published between March 1 and April 30 in a local newspaper, listing known noxious species and reminding landowners of their control duty. Where general notice isn't enough, the Weed Superintendent can serve an individual notice on a specific landowner with instructions on how and when to control a named species, and that notice must disclose the possibility of a civil penalty and a two-working-day window to appeal it under Idaho Code sections 22-2408 and 22-2409.