We all share responsibility for protecting Washington State from noxious weeds. This site can help you learn how to do your part.

Learn More

Noxious weeds are invasive, non-native plants that threaten agricultural crops, local ecosystems, or fish & wildlife habitats.

The term ‘noxious weeds’ includes non-native grasses, flowering plants, shrubs and trees. It also includes aquatic plants that invade wetlands, rivers, lakes and shorelines.

About half of all invasive, noxious weeds are escapees from gardens; the rest are plants accidentally introduced to Washington through human travel and trade.

Learn More about WA's Noxious Weeds Laws

Get Involved in the Noxious Weed Listing Process

Noxious Weeds Affect Us All

Dangerous to Livestock

Noxious weeds crowd out desirable forage for cattle, sheep, goats, horses, or other livestock. Some noxious weeds, such as yellow starthistle, also have spines that can injure livestock. Several are also toxic to livestock if eaten, many even retaining their toxicity when dried and baled in hay.

Cows in field

Reduced Fishing Opportunities

Noxious weeds can reduce fishing opportunities for anglers as they can make habitats less hospitable for fish and can reduce the oxygen level in the water, which can suffocate fish.

Dead Fish

Can Be Toxic to Humans

Some Noxious Weeds are toxic to humans! Contact with giant hogweed's sap, which is on top of the quarantine list this year, can leave painful, third-degree burns.

If you think you have ingested toxic plants, call 911, please go to the emergency room, or contact the Washington Poison Center at 1-800-222-1222.

Giant Hogweed Scars

Limit Wildlife Habitat and Reduce Wildlife Viewing and Hunting

Noxious weeds take over native plant communities and change the habitat upon which wildlife depend for food and shelter. The lack of forage forces them to search elsewhere for food and affects hunting and wildlife viewing opportunities. 

Rocky Mountain Elk  Na Merm

Destructive to our Trails and Roads

Noxious weeds negatively impact trail riding opportunities. Himalayan blackberry both blocks trails and can cause injury due to its sharp thorns. Puncturevine's sharp-spined seeds can rip right through tires, stick to shoes, pierce the paws of dogs, and really hurt when touched, making it a serious nuisance for bicyclists, hikers, dogs, and other park visitors.

Puncturevine on Tire

Degrade Wetland Habitat

Many aquatic and wetland noxious weeds degrade aquatic habitat. For example, parrotfeather forms dense mats that choke streams and ponds, reduce water flow and oxygen levels in the water, and displace native aquatic plant communities, which had provided valuable habitat for fish, amphibians, invertebrates, and other wildlife.


Displace Native Species and Reduce Biodiversity

Many noxious weeds such as knapweeds,leafy spurge, and Scotch thistle can convert rangeland and grassland, which contain a rich array of native grasses and wildflowers, into monocultures that are less palatable for grazing animals.

Rush Skeletonweed Infestation

Injure Trees and Forests

Shade-tolerant species such as garlic mustard can rapidly outcompete native plants and reduce the forest understory biodiversity. Woody vines like white bryony scramble up trees and make them weak and vulnerable. Fast-growing shrubs like English hawthorn can form dense stands that displace native woodland shrubs and regenerating trees.

Invaders In The Park

Increase Fire Hazards

Many noxious weeds and other invasive plants such as cheatgrass produce more dry biomass than the native plants they displace, creating a serious fire hazard. Noxious weeds like Scotch broom and Dalmatian toadflax are often among the first species to emerge following these devastating wildfires.

Burned plants

Reduce Property Values

Many noxious weeds can significantly reduce property values. Once noxious weeds monopolize rangeland and farmland, it can be very expensive to control the plants and restore the land back to a functional condition. 

Img 1029

Harm Important Riparian Habitat That Salmon Depend On

Fast-growing invasive plants can transform riverbanks by restricting access to water, increasing soil erosion, displacing native vegetation, reducing available sunlight, and altering the nutrient cycle. The degradation of habitat caused by noxious weeds pose a serious threat to our native plants as well as salmon and other wildlife.

River Bank Infestation 2

Damage Infrastructure and Harbor Rats in Urban Areas

Noxious weeds are also costly in suburban and urban areas. Invasive knotweeds can damage infrastructure by growing through pavement, pipes, and septic systems. Scrambling vines such as English ivy and white bryony can down trees and powerlines and cause structural damage to fences. They also harbor rats and other vermin.

Img 0992

Raise Food Prices and Cost Farmers Millions

Noxious weeds cost farmers, ranchers, and orchardists millions of dollars in control efforts and lost crop production, which can contribute to higher prices of food for all of us. 

Lincon County Fields

Reduce Visibility and Access on Roads

Noxious weeds on roadsides are more than just an eyesore! They also reduce visibility and utility right-of-way access. Additionally, noxious weeds on roadways aid to facilitate the movement of noxious weeds to other parts of our state and even to other states. 

Bad Roadside 2

Interfere with Commercial Timberland Reforestation

The majority of forested land in Washington is commercial timberland and some noxious weeds interfere with the reforestation process. For example, it was estimated in 2014 that Scotch broom alone cost Oregon $44.8 million in reduced timber production per year.

Img 7733

A Burden to Boaters and Swimmers

Submerged and floating-leaved aquatic noxious weeds can form dense mats that limit swimming areas and can even pose a drowning hazard. They also block waterways for boaters and paddlers, clog boat propellers, and plant fragments infest new water bodies by clinging to boats, trailers, and equipment.