Invasive Plants

Invasive species can have a negative impact on the health and function of our streams, wetlands and lakes in Snohomish County. Invasive species displace native vegetation, impair water quality and contribute to streambank erosion. The removal and control of these species is very important to improving the health of our aquatic areas.

Japanese Knotweed

A large patch of Japanese Knotweed on the bank of a river channel

English Ivy

A patch of English Ivy

Yellow Flag Iris

A patch of Yellow Flag Iris

Yellow Archangel

A patch of Yellow Archangel

Reed Canary Grass

A field of Reed Canary Grass

English Laurel

An English Laurel plant

The resources below can help in identifying and controlling invasive species.

  • Snohomish County Noxious Weeds
    The Snohomish County Noxious Weed Control Board is a great resource to find information on weed infestations in Snohomish County. Additionally, they are a great resource for identifying weeds and for information on control options. The website also includes an option to report noxious weeds and their location.
  • King County Noxious Weeds
    King County Noxious Weeds has several resources for common invasive species that are also present in Snohomish County. The website contains several best management practice factsheets for common weeds in Snohomish County including blackberry, knotweed, yellow flag iris and several other species.
  • WA State Noxious Weed Board
    The Washington State Noxious Weed Board determines which weeds should be listed statewide. The website also includes information on state weed laws and on weed identification and control.
  • Weed Control Videos
    Videos produced by West Multnomah Soil & Water Conservation District outline control methods for several common weeds found in Snohomish County.