This Class A noxious weed has a limited distribution in Washington State and has not been observed in King County. Eradication of this Class A weed is required throughout Washington State. This species is also on the Washington quarantine list (known as the prohibited plants list) (external link) and it is prohibited to transport, buy, sell, offer for sale, or to distribute plants or plant parts, seeds in packets, blends or "wildflower mixes" of this species, into or within the state of Washington. Slenderflower thistle invades pastures, meadows, and fields, displacing native and/or beneficial forage species.
Additional information on annual bugloss
What to do if you find this plant in King County, Washington
Please notify us if you see slenderflower thistle growing in King County. Our program staff can provide the property owner or appropriate public agency with site-specific advice on how best to remove it. Also, because slenderflower thistle is not established in King County, we have an opportunity to stop it from spreading if we act quickly. We map all known locations of regulated noxious weeds such as slenderflower thistle in order to help us and others locate new infestations in time to control them.