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Noxious weeds

King County, Washington

To offer a suggestion or report an error on the King County Noxious Weeds website, please contact Sasha Shaw, education specialist.

Noxious weed lists and laws

Noxious weeds in King County (click here to go to current King County Weed List)

Garlic mustard, a Class A noxious weed - click for more informationThe King County Noxious Weed Control Board administers the Washington State noxious weed law in King County. Each year, the Board adopts the King County Noxious Weed List, which specifies which noxious weeds property owners are required to control in the county. The county weed list includes all Class A weeds on the state noxious weed list, all Class B weeds designated by the state for control in the county, and any additional Class B or C weeds that are designated by the county weed board for required control in the county. All Class A, B and C weeds on the county weed list need to be controlled by the property owner.

  • Class A Weeds: Non-native species whose distribution in Washington is still limited. Preventing new infestations and eradicating existing infestations are the highest priority. Eradication of all Class A plants is required by law throughout Washington. 
  • Class B Weeds:  Non-native species presently limited to portions of Washington. Species are designated for control in regions where they are not yet widespread. Preventing new infestations in these areas is a high priority. In regions where a Class B species is already abundant, control is decided at the local level, with containment as the primary goal.
  • Class C Weeds:  Noxious weeds that are typically widespread in Washington or are of special interest to the state’s agricultural industry. The Class C status allows counties to require control if locally desired or to choose to provide education or technical consultation.

Controlling weeds means not letting weeds reproduce. Usually, that means not letting them go to seed. Legally, control means to prevent the dispersal of all propagating parts capable of forming a new plant.

In addition to the regulated weeds, the county weed list includes additional species that landowners are not required to control but for which the county provides technical assistance and information:

  • Non-Regulated Noxious Weeds: State-listed Class B and C noxious weeds not designated for mandatory control in King County but that have negative impacts for the people and the environment of the county.  Often these species are already widespread in the county and requiring control countywide would not be feasible.  The county weed board encourages landowners to control these species where possible and to avoid introducing them to the county.
  • King County Weeds of Concern: These are additional non-native, invasive plant species that are not classified as noxious weeds on the state list but are problematic in King County. These species often impact and degrade native plant and animal habitat. The County Weed Board recognizes these plants are invasive and is collecting information and providing education on control. The Board encourages and recommends control and containment of existing populations and discourages new plantings, but control is not required.

Understanding the Washington State Noxious Weed Law

Noxious weeds are non-native plants that, once established, are highly destructive, competitive and difficult to control. They have economic and ecological impacts and are very difficult to manage once they get established. Some are toxic or a public health threat to humans and animals, others destroy native and beneficial plant communities.

To help protect the state's resources and environment, the Washington State Noxious Weed Board adopts a state weed list each year (Chapter 16-750 WAC), in accordance with the state noxious weed law (Chapter 17.10 RCW). Noxious weeds are separated into classes A, B, and C based on distribution, abundance, and level of threat (how dangerous the plants is to humans, animals, private and public lands, and native habitats).english ivy overtaking a stop sign

The goal of the state weed law is to prevent the spread of new and recently introduced weeds while it is still feasible to do so. Class A weeds are the most limited in distribution and therefore the highest priority for control. Class B and C weeds vary in priority based on local distribution and impacts. Not all weeds are classified as noxious weeds in Washington State and only species that are not native to the state are considered for noxious weed listing. Between November and April, any person may request a change to the Washington State Noxious Weed List for the following year. For more information on the state's weed listing process and how you can participate, please contact the Washington State Noxious Weed Board.

Noxious weeds are designated for control in all or parts of the state based on where it is still feasible to eradicate or contain the weeds. Property owners, both public and private, are required to control Class A weeds and any Class B or C weeds that are designated by the state or selected by the county weed board for control in their area. "Control" as defined in WAC 16-750 means to prevent the dispersal of all propagating parts capable of forming a new plant. Class A weeds need to be eradicated or removed entirely and Class B and C weeds designated or selected for an area need to be controlled to prevent their spread. For more information, see Washington's Noxious Weed Laws.

For purposes of designating required control areas for Class B weeds, Washington is divided into six regions. King County is in Region 2.

The state noxious weed law also restricts the sale and transport of certain noxious weeds under its quarantine section. For more information on these quarantines, contact the WSDA Nursery Inspection Program or review the Quarantine List for the state of Washington.