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Slenderflower thistle identification and control: Carduus tenuiflorus

Slenderflower thistle identification and control

Carduus tenuiflorus

Slenderflower thistle plant
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)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. For more information on noxious weed regulations and definitions, see Noxious weed lists and laws

Slenderflower thistle invades pastures, meadows, and fields, displacing native and/or beneficial forage species.

Additional information on slenderflower thistle

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.

Report slenderflower thistle in King County, Washington

Locate slenderflower thistle in King County, Washington

Related information

Related agencies

Program offices are located at 201 S. Jackson St., Suite 600, Seattle, WA 98104. To contact staff, see the Noxious Weed Control Program Directory, send an email, or call 206-477-WEED (206-477-9333).