Washington State Noxious Weed Control Board

10/23/2026

Italian thistle, Carduus pycnocephalus, grows dense thickets of very spiny rosettes in winter, preventing establishment of desired plants like livestock forage and native plants. It looks very similar to slenderflower thistle, but both are Class A Noxious W**ds in Washington State and should be eradicated when they are found.

10/09/2026

French broom, Genista monspessulana, is a Class A Noxious W**d in Washington State, which looks a lot like Scotch broom. French broom flowers only grow at branch tips, the stems are usually more ridged, and the leaves are lightly hairy all over (instead of just around the edges).

10/01/2026

For spotted lanternflies, a tree of heaven is the perfect hotel to check in to—and never check out. This invasive plant is a favorite host of the spotted lanternfly, partially because they both come from the same place in Asia. A tree of heaven is the ideal place for a spotted lanternfly to eat, lay eggs, and spread its population. It’s like getting a taste of home while traveling! (such a lovely taste)

Spotted lanternflies also eat native plants and crops like fruit trees, threatening agriculture and forest health. Let’s keep these destructive pests from checking in to Washington by controlling tree of heaven, which frequently grows in suburban and urban areas along roads, fences, buildings, and recently disturbed land.

Learn how identify and report this invasive plant at https://agr.wa.gov/departments/insects-pests-and-w**ds/w**ds/tree-of-heaven

Photos courtesy of Lawrence Barringer, Pennsylvania Department of Agriculture, Bugwood.org, and A. Smith, ODNR Division of Forestry

09/11/2026

Grasses are very hard to identify, even for trained botanists! Take a gander at these pictures of False Brome, Brachypodium sylvaticum, to help you recognize the hairy leaf blades and drooping seed heads of this Class A Noxious W**d, for when it starts showing itself in our forest understories next summer!

09/03/2026

Turkish thistle, Carduus cinereus, is a Class A Noxious W**d in Washington State that readily spreads across rangeland and grassland. This negatively impacts native species and livestock forage.

08/28/2026

Purple loosestrife, Lythrum salicaria, is a Class B Noxious W**d in Washington State. That means it is required for control in many places, but not everywhere! As the negative review says, it is particularly harmful in our wetland habitats!

If our Washington wetlands could write reviews, you can bet they’d give zero stars to purple loosestrife.

This noxious w**d outcompetes native plants for resources, alters wetland structure and function, clogs waterways and irrigation systems, affects agricultural production, and reduces the pasture quality for livestock grazing.

It’s a total buzzkill!

This plant is on Washington’s Noxious W**d Seed and Plant Quarantine list, meaning it’s prohibited to transport, buy, sell, offer for sale, or distribute leafy spurge plants, plant parts, or seeds.

You can help prevent the spread by removing any plants from gardens and not planting them to begin with.

Learn more: https://invasivespecies.wa.gov/priorityspecies/purple-loosestrife/

Photo courtesy of Steve Dewey/Utah State University

08/19/2026

In addition to our beautiful native Oregon ash, ash trees are also popular plantings in gardens and along roadsides throughout Washington. The emerald ash borer will put all of these amazing trees at risk!

https://agr.wa.gov/about-wsda/news-and-media-relations/news-releases?article=47256

📢 : Emerald ash borer has been detected in Washington State near Vancouver. This highly invasive and destructive pest kills up to 99% of ash trees. So far, this pest has not been eradicated in any area where it has been discovered.

Washington has prepared for the arrival of this pest by creating resources for government organizations and individuals. Check out our press release to learn more about this pest and get resources on what you can do now to prepare. https://agr.wa.gov/about-wsda/news-and-media-relations/news-releases?article=47256

08/12/2026

Waterthyme, Hydrilla verticillata, is an aquatic Class A Noxious W**d in Washington State. Brought in as an aquarium plant, it makes a dense mat, which shades out all other aquatic life and impeding recreation.

It is a perfect example of why to never dump your aquarium into the wild!

08/03/2026

Garlic mustard, Alliaria petiolata, is a Class A Noxious W**d in Washington, which heavily impacts forest understories.

It can be identified by its kidney/heart shaped leaves with wavy to toothed edges, quarter inch white flowers, and its garlic scent!

07/28/2026

Clary sage, Salvia sclarea, is a Class A noxious w**d in Washington State, which invades rangeland, reducing habitat for native species and livestock. It looks similar, and is closely related to, meadow clary and Mediterranean sage, which are also Class A w**ds here!

https://www.nwcb.wa.gov/w**ds/clary-sage