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Noxious weeds

King County, Washington

To offer a suggestion or report an error on the King County Noxious Weeds website, please contact Sasha Shaw, education specialist.

Brazilian elodea
Egeria densa

Brazilian elodea in handThis noxious weed is a submersed, freshwater perennial plant found in both still and flowing waters including lakes, ponds and quiet streams. Brazilian elodea tends to form dense monospecific stands that can cover hundreds of acres.

Brazilan elodea in Lake DoloffNative to Brazil and Argentina, Brazilian elodea is a popular aquarium plant often sold in pet stores and available in school science kits under the name Anacharis. When it is introduced into freshwater, it forms dense beds that reduce water quality and impede recreational activities. It is illegal to sell this plant in Washington State.

Brazilian elodea in Lake Fenwick - click for larger imageThis aggressive aquatic plant has spread into many western Washington lakes including Lakes Washington, Union, Sammamish, Fenwick, and Doloff in King County. State officials in Oregon consider Brazilian elodea to be their worst aquatic plant problem but in Washington there is still a chance to contain it. In King County, most small lakes and waterways are still free of this weed, so there is still a chance to keep this aquatic pest from impacting most of King County.

Brazilian elodea flowering Brazilian elodea closeupIdentifying Brazilian elodea can be tricky so be sure to get an expert to confirm the species before planning any control measures. The plant grows mostly underwater but can form dense mats along the surface. Leaves grow in whorls around the stem making a cylindrical shape and the stems are very leafy compared to the native elodea, common waterweed (Elodea canadensis). There are usually 4 to 8 leaves in a whorl and the leaf edges appear smooth to the naked eye (native elodea has 3 leaves in a whorl). Small white flowers appear from spring to late summer. They have three petals and float on or rise above the water's surface on thread-like stems.

Legal status in King County, Washington

Public and private landowners are required to control infestations of Brazilian elodea that occur on their property in King County, Washington except in lakes Dolloff, Fenwick, Union, Washington, and Sammamish, and the Sammamish River. Brazilian elodea is a Class B Noxious Weed in Washington, first listed in 1993. It is designated by the Washington State Noxious Weed Control Board for required control in King County except in areas as described above. It is on the list of Regulated Class B Noxious Weeds in King County. For more information, see Noxious Weed Lists and Laws or visit the website of the Washington State Noxious Weed Control Board.

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 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.

Additional information on Brazilian elodea

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

Please notify us if you see brazilian elodea 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.  We map all known locations of regulated noxious weeds such as brazilian elodea in order to help us and others locate new infestations in time to control them.

Brazilian elodea photos - click thumbnail to see larger image

Brazilian_elodea_flower_closeup Diver with Brazilian elodea in Lake Union Handful of Brazilian elodea in Thurston County Brazilian elodea on boat motor Dense patch of Brazilian elodea in Thurston County Dense infestation of Brazilian elodea in Thurston County

Report brazilian elodea in King County, Washington

Locate brazilian elodea in King County, Washington

Related information

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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).