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Frequently asked questions

Frequently asked questions

Noxious weeds are non-native plants that are highly destructive, competitive and difficult to control or eliminate. They have been introduced accidentally or as ornamentals in peoples' gardens. Some are poisonous to humans and livestock and most grow rapidly and overwhelm desirable vegetation. They can reduce crop yields, destroy beneficial native habitat, damage recreational opportunities, clog waterways, and diminish land values.

Beginning in 1998, the King County Noxious Weed Control Board asked the King County Council to put a special assessment on each property tax bill to fund the weed control program, as authorized by state law RCW 17.10. Currently the assessment is $6.20 a year per parcel plus 44 cents per acre on all properties in the county with the exception of property classified as forest land and federal and tribal properties. Property classified as forest land, as defined in RCW 84.33.035, which is used solely for the planting, growing or harvesting of trees and which is typified by canopies so dense as to prohibit the growth of an understory, is assessed at the rate of 62 cents per parcel plus 4 cents per acre. As allowed under the state's noxious weed law, many Washington counties now have noxious weed assessments on their property tax bills so that weed programs can have a dedicated source of funding.

A state law passed in 1969 mandates all counties to have a program to combat noxious weeds. King County was under court order to operate a weed control program as result of a 1995 lawsuit by the State of Washington. The suit was prompted by complaints from neighboring counties that King County was not controlling noxious weeds as required by state law.

The King County Noxious Weed Control Board was established to direct the state mandated program as required by the court order. The board consists of five unpaid citizen volunteers who represent five districts that cover the entire county. The board meets monthly and provides vision and direction to the weed control program. While the program’s staff are technically county employees, they are hired, directed and supervised by the citizen board.

The King County Noxious Weed Control Program focuses on education, prevention, technical assistance and control of noxious weeds through voluntary compliance. Preventing the spread of weeds is more effective and less costly than eradication.

From March through October, when weeds are growing the most rapidly, the program employs field staff to survey public and privately owned lands in King County for noxious weeds and to work with landowners to achieve weed control. Much of the survey work is the result of citizens reporting infestations and asking for information and assistance in getting rid of noxious weeds on their property. Field staff finds additional infestations as they travel the county.

Once an infestation is identified, the landowner is given a variety of options, including hand pulling, mowing or cutting; advice on better pasture management; and using the most effective and least harmful methods of applying herbicides. The King County Noxious Weed Control Board does not require people to use herbicides to control weeds. The majority of weed infestations are controlled voluntarily by landowners. Less than 1% of the known weed infestations are controlled by the weed program and, as authorized by state law, the landowners are billed.

Weeds are everyone's problem. Even landowners who don't currently have weeds can be harmed by weeds that spread from adjacent lands. Seeds are carried by wind and cars and the invasive nature of these plants means that no land is immune to their spread. Prevention of new infestations and introductions is a top priority of the King County Noxious Weed Control Program.

When the state passed the law mandating that counties control noxious weeds, it gave counties only two ways to fund the work. Counties can either use general fund money, for which there is a lot of competition, or they can assess a special dedicated fee on property. It is not a tax, it is a regulatory fee for a service that is available to all landowners and it cannot be imposed selectively. The county has limited authority to fine people who have weeds. Everyone benefits when we control and prevent the spread of noxious weeds.

The State Noxious Weed Board, a group of citizen volunteers representing all areas of the state, annually adopts and publishes a list of weeds to be controlled or eradicated based on public comment and input from county weed boards. The King County Weed Board customizes the state list and puts out a list of King County's priority weeds that are required by law to be controlled by the property owner. The King County Noxious Weed Control Program, which can be reached at (206) 477-9333 or, has staff with scientific knowledge of weeds and can provide color photos and descriptions of noxious weeds to help citizens identify and eliminate noxious weed infestations.

King County agencies and departments (such as Parks, Roads, WLRD Drainage Services, Transit, etc) are notified of and are required to control noxious weed infestations, much the same way private landowners are notified. The perception that King County is not controlling weeds on County property is a frequently heard and inaccurate one. Our records indicate that there are as many noxious weeds on private property as there are on County lands. The public is much more likely to see weeds on public lands, and it is easier to notice where the weeds are, rather than where they are not or where they have been controlled. The noxious weed program staff can provide records of where noxious weeds have been found and controlled on County lands and report annually about the level of control achieved on County owned and managed lands.  The staff also seek out information from the public on where they see noxious weeds on County lands and roadsides so they can notify the appropriate agency and make sure effective weed control is achieved in a timely manner.

Noxious weeds are found everywhere in King County—in urban, suburban and rural areas; on developed and undeveloped land, farmland, forests and other natural open spaces as well as in lakes, rivers, streams and Puget Sound.  Some of the noxious weeds found in King County include:

  • Giant hogweed - predominantly an urban weed and an escaped garden ornamental, its sap can cause skin blistering and scarring.
  • Garlic mustard - one of the worst forest understory weeds in the Great Lakes and Northeastern United States, it is now spreading from urban to rural areas in the Pacific Northwest, threatening woodlands and sensitive habitats.
  • Tansy ragwort - likely to infest pastures and roadsides, it has toxins that can be fatal to cows and horses and it reduces pasture quality.
  • Spotted knapweed - threatens wildlife habitat, pastures, and grasslands by displacing beneficial species.
  • Purple loosestrife - grows in wetlands and along lakes, rivers and streams; it chokes out wildlife habitat and clogs drainage ditches and irrigation canals. Purple loosestrife invades wetlands in 48 states, crowding out native plants and endangering the wildlife that depend on the native plants.
  • Parrotfeather - chokes out prime salmon habitat and reduces availability of refuge, exposing salmon to predators.
  • Invasive knotweeds - aggressive, hard to control perennials that are destroying riparian habitat in the Pacific Northwest.

For more information on what noxious weeds are found in King County, see the noxious weed map for the county and read the Annual Report of the King County Noxious Weed Control Board.

  • Non-native invasive weeds across the US cost an estimated $26.4 billion per year in agricultural economic losses.
  • Approximately 420,000 acres of grassland and national forests in the Pacific Northwest are reported to have been degraded by invasive weeds
  • Noxious weeds are a leading contributing cause of species endangerment.
  • Purple loosestrife, which chokes out wildlife habitat, now invades wetlands in 48 states at an estimated cost of $45 million a year for control and lost land use.
  • Other noxious weeds can significantly reduce the recreational value of public open space and aquatic areas. For example, the aquatic weeds Brazilian elodea and hydrilla can clog waterways, seriously disrupting boating and swimming activities.
  • Detecting and responding quickly to new weed infestations and introductions.
  • Surveying/mapping noxious weed infestations locations countywide.
  • Offering landowners technical expertise to achieve high rates of weed control and voluntary compliance with the state weed law.
  • Providing educational services to the public through informational workshops and publications.
  • Conducting research on the best methods for weed control and eradication in King County.
  • Assisting other agencies and non-profit groups with weed identification, control and eradication.
  • Coordinating weed management efforts by working with volunteer and community groups.