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Eurasian watermilfoil identification and control: Myriophyllum spicatum

Eurasian watermilfoil identification and control

Myriophyllum spicatum

milfoil plantThis Class B noxious weed is widespread throughout Washington State. Control is not required but recommended in King County. 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 of this species, into or within the state of Washington. It is further prohibited to intentionally transplant wild plants and/or plant parts of this species within the state of Washington. For more information see Noxious weed lists and laws or visit the website of the Washington State Noxious Weed Control Board.

Eurasian watermilfoil is a submerged aquatic plant that is present in many lakes in King County, especially lakes with public boat launches. In order to prevent further spread of this and other aquatic weeds, boaters should clean all vegetation from boats and trailers before moving between lakes. If Eurasian watermilfoil is detected early enough, it may be possible to control it.

Additional information on Eurasian watermilfoil

What to do if you find this plant in King County, Washington

Because Eurasian watermilfoil is so widespread, property owners in King County are not required to control it and we are not generally tracking infestations. We can provide advice on how to control Eurasian watermilfoil, but there is generally no legal requirement to do so.

Eurasian watermilfoil photos

milfoil on boat motor
milfoil in Lake 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).