OLYMPIA – First found growing in Thurston County in the Chehalis River in 1998, populations of the noxious weed Brazilian elodea have exploded over the past two seasons.
More than 7,000 lbs of Brazilian elodea was removed from the Chehalis River July 19-July 29, by a contractor working for Thurston County Noxious Weed Control.
Brazilian elodea is native to South America . It has been imported to North America , as well as many countries around the world, as an aquarium plant (often sold under the name of Anacharis). Brazilian elodea is a submersed, freshwater perennial. It roots in water up to 20 feet deep, with the stems growing up to the surface of the water, where they form dense mats. Roots grow from the stem nodes; leaves and stems are bright green. The plant is spread by fragmentation. Brazilian elodea has four (sometimes eight) leaves, while the native elodea, has three.
Dense stands affect water movement, water quality, recreational uses, and navigation. The plant can also trap sediment thereby impacting native plants and fish. Brazilian elodea grows rapidly in the spring, shading out slower growing native plants. It is illegal to sell this plant in the state of Washington .
Diver dredging (suction dredging) was used on a one-mile stretch of the Chehalis River in Thurston County at mile 60. Diver dredging is a method where divers use hoses attached to small dredges to vacuum plant material out of the river. This is primarily a removal process following dislodging of the roots by divers.
The purpose of diver dredging is to effectively remove all of the plant biomass including the roots. The divers use the suction device for Egeria disposal only. The water is returned back to the river and the plant material is then disposed of.
This project was funded by the Washington Department of Natural Resources and administered through the Thurston County Noxious Weed Control Department.