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Invasive Species

Invasive non-native plants are one of the biggest threats to native ecosystems, second only to habitat conversion. Washington’s forested communities, prairies, shrub-steppe, grasslands, riparian and wetland habitats are all vulnerable.

Invasive non-native plants compete with native plants in many ways including: occupying space, changing the structure of the plant community, causing physical and chemical alterations of the soil, and covering and shading native plants. Invasive plants interfere with animal life, too, by altering the structure of their habitat and by eliminating favored food plants through competition. Invasive plants are spread both by human activity and by animals that eat them and carry their seeds. Each of the plant communities identified by WNPS for special focus is threatened by invasive plants.

Garry Oak and its associated prairies are particularly threatened by Scot’s broom which invades and thoroughly dominates an area. Knapweeds and cheat grass have done extensive damage to eastern Washington’s native shrub-steppe. While purple loosestrife, spartina and knotweeds continue to threaten Washington’s wetlands and riparian habitats.

Links to other sites:

Washington State Noxious Weed Control Board

Washington Invasive Species Coalition

Invasive and Exotic Insects, Diseases, and Weeds: Information and Images