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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.

Regulated Class B noxious weeds, 2014 list
(control is required for these species in King County)

Common name

Scientific name
blueweed, viper's bugloss (external link)  Echium vulgare
Brazilian elodea (see note 1 below) Egeria densa
bugloss, annual Anchusa arvensis
bugloss, common Anchusa officinalis
camelthorn (external link)  Alhagi maurorum
common reed (non-native genotypes) Phragmites australis
Dalmatian toadflax Linaria dalmatica ssp. dalmatica
fanwort Cabomba caroliniana
gorse Ulex europaeus
grass-leaved arrowhead (external link) Sagittaria graminea
hairy willowherb Epilobium hirsutum
hawkweeds: all non-native species and hybrids of the meadow subgenus (see note 2 below) Hieracium, subgenus Pilosella
hawkweeds: all non-native species and hybrids of the wall subgenus (see note 2 below) Hieracium, subgenus Hieracium
hawkweed, orange Hieracium aurantiacum
hawkweed oxtongue (external link) Picris hieracioides
hoary alyssum (external link) Berteroa incana
houndstongue Cynoglossum officinale
indigobush Amorpha fruticosa
knapweed, black Centaurea nigra
knapweed, brown Centaurea jacea
knapweed, diffuse Centaurea diffusa
knapweed, meadow Centaurea jacea x nigra
knapweed, Russian Acroptilon repens
knapweed, spotted Centaurea stoebe
kochia Kochia scoparia
loosestrife, garden Lysimachia vulgaris
loosestrife, purple Lythrum salicaria
parrotfeather Myriophyllum aquaticum
perennial pepperweed Lepidium latifolium
policeman's helmet Impatiens glandulifera
rush skeletonweed Chondrilla juncea
saltcedar Tamarix ramosissima
spurge, leafy Euphorbia esula
sulfur cinquefoil Potentilla recta
tansy ragwort (see note 3 below) Senecio jacobaea
thistle, musk Carduus nutans
thistle, plumeless (external link) Carduus acanthoides
thistle, Scotch Onopordum acanthium
velvetleaf Abutilon theophrasti 
water primrose Ludwigia hexapetala
white bryony (external link) Bryonia alba
wild chervil (external link) Anthriscus sylvestris
yellow floating heart Nymphoides peltata
yellow nutsedge Cyperus esculentus
yellow starthistle Centaurea solstitialis
1. Brazilian elodea is designated for control throughout King County except in Lake Washington, Lake Sammamish, Lake Union, Lake Fenwick, Lake Doloff and the Sammamish River.
2. Non-native yellow-flowered hawkweeds (Hieracium species): the 11 separate listings of yellow-flowered hawkweeds that were previously on the noxious weed list are now consolidated into two Class B listings by subgenus - meadow (Pilosella) and wall (Hieracium). In general, the meadow subgenus species have stolons present, have no or few leaves on the stems, and have leaf edges that are smooth or minutely toothed. The wall subgenus species in contrast generally lack stolons, have stem leaves, and have leaf edges that are conspicuously toothed or lobed.
3. Tansy ragwort is not designated by the State Weed Board for control in King County, but has been selected by the King County Weed Board for required control in all areas of King County.

King County Noxious Weed List

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Related information

Related agencies


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).