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Lakes

Lakes in King County, Washington

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King County, Washington lakes

Brazilian elodea
(Egeria densa)

Class B Noxious Weed

Brazilian elodeaSee a color photo comparing Brazilian elodea to native elodea.

History

As its name indicates, Brazilian elodea is from South America and was originally introduced to North America for aquarium use. Up until 1996 it was commonly sold in Washington pet stores and plant nurseries.

Method of spread

Brazilian elodea reproduces by the spread of plant fragments. Branches sprout from "double nodes" located at intervals along the stems. The plant is probably spread most often when aquariums are dumped in our lakes or when boaters carry it from an infested lake into an uninfested waterbody.

Brazilian elodea grows very well in Washington lakes once introduced and soon forms dense mats that choke out our native aquatic plants. These mats are unsightly, interfere with swimming, boating and fishing, and provide poor habitat for fish.

Methods of control

Brazilian elodea is difficult to control because it has few natural predators. Some aquatic herbicides are effective in controlling its growth. Grass carp have shown promise as a control technique, but are not an option in lakes with anadromous fish runs (salmon). Harvesting allows small plant fragments to spread to new areas, limiting its success as a control method.

Identification

  • commonly confused with hydrilla and American waterweed (Elodea canadensis)
  • leaves arranged in whorls of four
  • stems are dense with bright green leaves
  • flowers are small, white, and have three petals
  • leaf structure looks similar to hydrilla but Brazilian elodea does not produce tubers


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For questions about aquatic weeds and lakes in King County, please contact Sally Abella, senior engineer, Lake Stewardship Program.