Invasive species are plants, animals, or organisms that spread so quickly that they harm other wildlife.

They are not native to Washington and were brought here by someone or something. Because they are new to this state, natural predators often don’t exist, allowing them to spread at alarming rates.

Most non-native species are useful, such as farm animals and crops. Just a handful of non-native species cause problems.

Invasive Species Are Everyone’s Problem

Invasive species can take over your garden, favorite swimming lake, or hiking trail. They out-compete native plants and animals for scarce resources, changing the landscape. Invasive species damage farms and forests as well as lakes, rivers, and marine waters. They cause hundreds of billions of dollars worth of damage. Farmers, foresters, and homeowners also spend hundreds of thousands of dollars to control invasive species. Invasive species are not just a danger in Washington. They are one of the leading threats to the world’s diversity of plants, animals, and the places they live. For example, invasive species impact nearly half of the plants and animals listed as threatened or endangered under the U.S. Endangered Species Act.

Some Examples


Washington has been fighting to control invasive plants since settlers first arrived. For many years, the agricultural community led the fight against invasive plants. Today, we recognize that invasive plants also harm lakes, streams, wetlands, and ecosystems. Invasive plants displace native species that wildlife depend on for food. See the top management priorities.

To combat invasive plants, Washington has a system of county weed boards and local weed districts, and laws that require landowners to control invasive plants on their properties. The traditional, legal term for invasive plants is noxious weeds. The Washington State Noxious Weed Control Board maintains a list of plants that landowners are required to control, helps coordinate local weed boards, and provides public education materials. The Department of Agriculture maintains a list of all plants and seeds whose sales are prohibited in Washington.


Insects, snakes, birds, lizards, fish, amphibians, and mammals can dramatically alter native habitats and out-compete native species. To see a list of all potentially invasive aquatic species prohibited from the state please, visit the Washington Department of Fish and Wildlife’s Aquatic Invasive Species page.


Exotic pests are estimated to cost the United States $137 billion in crop damage each year. Pests, such as the apple maggot, have the ability to attack not only apples, Washington’s top cash crop, but also cherries, pears, plums, and apricots. To find out more about exotic pests, visit the Washington Department of Agriculture’s Web site.