Controlling noxious weeds helps ecosystems, agriculture, and people. To use the most effective methods while also minimizing any unintended negative impacts to people and the environment, the King County Noxious Weed Control Board directs the noxious weed control program to practice Integrated Pest Management and to choose methods that prevent harm to other organisms such as bees, fish, wildlife, and people.

Before controlling noxious weeds, learn about federal, state, county, and city regulations that might apply to your situation. In King County, read the King County Noxious Weed Control Regulatory Guidelines. This resource provides guidelines on regulations that relate to noxious and invasive weed control in King County including the State Noxious Weed Law (RCW 17.10), regulations relating to clearing and grading and critical areas, and regulations that protect clean water as they relate to control of noxious weeds.

The way you control noxious weeds also depends on the plant and the site. Controlling a handful of new tansy ragwort plants by your mailbox will require a different technique than removing ten acres of tansy ragwort spread throughout a pasture.

To help landowners choose the best control method for their weeds on their sites while minimizing impacts, the noxious weed program has developed Best Management Practices (BMP's). The BMP’s provide specific control recommendations and guidelines for different types of areas, as well as plant identification tips and impacts.

Best Management Practices (BMP's) for noxious weed control

Bittersweet Nightshade Control
Bittersweet nightshade (Solanum dulcamara)

Blackberry Control
Evergreen blackberry (Rubus laciniatus) and Himalayan blackberry (Rubus discolor, syn. Rubus armeniacus).

Brazilian Elodea/Egeria Control
Egeria/Brazilian elodea (Egeria densa)

Bull Thistle Control
Bull thistle (Cirsium vulgare)

Common Reed (Phragmites) Control
Common reed (Phragmites australis)

Common Tansy Control
Common tansy (Tanacetum vulgare)

Dalmatian Toadflax Control
Dalmatian toadflax (Linaria dalmatica ssp. dalmatica)

Diffuse Knapweed Control
Diffuse knapweed (Centaurea diffusa)

English Holly Control
English holly (Ilex aquifolium)

English Ivy Control
English ivy (Hedera helix) and Irish or Atlantic ivy (Hedera hibernica)

Fragrant Water Lily Control
Fragrant water lily (Nymphaea odorata)

Garden Loosestrife Control
Garden loosestrife (Lysimachia vulgaris)

Garlic Mustard Control
Garlic mustard (Alliaria petiolata)

Giant Hogweed Control
Giant hogweed (Heracleum mantegazzianum)

Gorse Control
Gorse (Ulex europaeus)

Hawkweed Control
Hawkweed species (Hieracium sp.) including orange hawkweed, yellow hawkweed, and other non-native invasive hawkweed species

Herb Robert Control
Herb Robert (Geranium robertianum)

Knotweed Control
Hybrid knotweed (Fallopia x bohemicum), itadori knotweed (Fallopia japonica), giant knotweed (Fallopia sachalinensis), and Himalayan knotweed (Persicaria wallichii)

Meadow Knapweed Control
Meadow knapweed (Centaurea × moncktonii)

Milfoil Control
Eurasian watermilfoil (Myriophyllum spicatum) and variable-leaf milfoil (Myriophyllum heterophyllum)

Milk Thistle Control
Milk thistle (Silybum marianum)

Old Man's Beard (Clematis) Control
Old man's beard (Clematis vitalba)

Parrotfeather Control
Parrotfeather (Myriophyllum aquaticum)

Policeman's Helmet Control
Policeman's helmet (Impatiens glandulifera)

Purple Loosestrife Control
Purple loosestrife (Lythrum salicaria)

Reed Canarygrass Control
Reed canarygrass (Phalaris arundinacea)

Scotch Broom Control
Scotch broom (Scot's broom) (Cytisus scoparius)

Spanish Broom Control
Spanish broom (Spartium junceum)

Spotted Knapweed Control
Spotted knapweed (Centaurea stoebe)

Sulfur Cinquefoil Control
Sulfur cinquefoil (Potentilla recta)

Tansy Ragwort Control
Tansy ragwort (Jacobaea vulgaris)

Wild Chervil Control
Wild chervil (Anthriscus sylvestris)

Yellow Archangel Control
Yellow archangel (Lamiastrum galeobdolon)

Yellow Flag Iris Control
Yellow flag iris (Iris pseudacorus)

More information on IPM and related topics

• Biological control
• Integrated pest management
• Bees and noxious weed control
• Aquatic plant management (Lake Stewardship Program)
• Information on identifying and controlling specific weeds

For site-specific weed control recommendations, please contact the noxious weed program at 206-477-WEED (206-477-9333) or by email.

Related information

• Agriculture in King County, Washington
• Northwest yard and garden
• Animals, plants and habitat
• Lake services and information
• Permitting and environmental review 

Related agencies

• Dept. of Natural Resources and Parks
• Water and Land Resources Division

Languages

Find information on noxious weed identification and control in multiple languages:

• Español (Spanish)
• Tiếng Việt (Vietnamese)
• 中文: 简体版 (Simplified Chinese)
• Af-Soomaali (Somali)
• русский язык (Russian)

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Program offices are located at 201 S. Jackson St., Suite 600, Seattle, WA 98104. To contact staff, see the Noxious Weed Control Program Directory, send an email, or call 206-477-WEED (206-477-9333).