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Regulated Class A noxious weeds
(eradication required throughout Washington State including King County)

Scientific name Common name State class
Alliaria petiolata garlic mustard  A
Brachypodium sylvaticum false brome  A
Butomus umbellatus flowering-rush  A
Carduus pycnocephalus (external link)  Italian thistle  A
Carduus tenuiflorus slenderflower thistle  A
Centaurea calcitrapa purple starthistle  A
Centaurea macrocephala bighead knapweed  A
Centaurea nigrescens Vochin knapweed  A
Clematis orientalis oriental clematis  A
Crupina vulgaris common crupina  A
Euphorbia oblongata (external link)  eggleaf spurge  A
Galega officinalis goatsrue  A
Genista monspessulana French broom   A
Glyceria maxima reed sweetgrass  A
Helianthus ciliaris Texas blueweed  A
Heracleum mantegazzianum giant hogweed  A
Hydrilla verticillata hydrilla  A
Isatis tinctoria dyers woad  A
Ludwigia peploides  floating primrose-willow  A
Mirabilis nyctaginea (external link) wild four o'clock  A 
Myriophyllum heterophyllum variable-leaf milfoil  A
Pueraria montana var. lobata kudzu  A
Salvia pratensis meadow clary  A
Salvia sclarea clary sage  A
Salvia aethiopis Mediterranean sage  A
Schoenoplectus mucronatus ricefield bulrush  A
Silybum marianum milk thistle  A
Solanum elaeagnifolium (external link) silverleaf nightshade  A
Sorghum halepense (external link) Johnsongrass  A
Spartina alterniflora smooth cordgrass  A
Spartina anglica common cordgrass  A
Spartina densiflora (external link)  dense flower cordgrass  A
Spartina patens salt meadow cordgrass  A
Spartium junceum Spanish broom  A
Thymelaea passerina (external link)  spurge flax  A
Zygophyllum fabago Syrian bean-caper  A

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

Scientific name Common name State class
Abutilon theophrasti velvetleaf  B 
Acroptilon repens Russian knapweed  B
Alhagi maurorum (external link)  camelthorn  B
Amorpha fruticosa (external link) indigobush  B 
Anchusa arvensis annual bugloss  B
Anchusa officinalis common bugloss  B
Anthriscus sylvestris
wild chervil  B
Berteroa incana (external link)  hoary alyssum  B
Bryonia alba (external link)  white bryony  B
Cabomba caroliniana fanwort  B
Carduus nutans musk thistle  B
Carduus acanthoides (external link)  plumeless thistle  B
Centaurea solstitialis yellow starthistle  B
Centaurea biebersteinii spotted knapweed  B
Centaurea nigra black knapweed  B
Centaurea jacea brown knapweed  B
Centaurea diffusa diffuse knapweed  B
Centaurea x moncktonii meadow knapweed  B
Chondrilla juncea rush skeletonweed  B
Cynoglossum officinale houndstongue  B
Cyperus esculentus yellow nutsedge  B
Echium vulgare blueweed, viper's bugloss  B
Egeria densa (see note 1 below) Brazilian elodea  B
Epilobium hirsutum hairy willowherb  B
Euphorbia esula leafy spurge  B
Geranium lucidum shiny geranium  B
Hieracium, subgenus Pilosella (see note 2 below) hawkweeds: all non-native species and hybrids of the meadow subgenus  B
Hieracium aurantiacum orange hawkweed  B
Hieracium sabaudum European hawkweed  B
Impatiens glandulifera policeman's helmet  B
Kochia scoparia kochia  B
Lepidium latifolium perennial pepperweed  B
Linaria dalmatica ssp. dalmatica Dalmatian toadflax  B
Ludwigia hexapetala water primrose  B
Lysimachia vulgaris garden loosestrife  B
Lythrum salicaria purple loosestrife  B
Myriophyllum aquaticum parrotfeather  B
Nymphoides peltata yellow floating heart  B
Onopordum acanthium Scotch thistle  B
Phragmites australis common reed (non-native genotypes)  B
Picris hieracioides (external link) hawkweed oxtongue  B
Potentilla recta sulfur cinquefoil  B
Sagittaria graminea (external link)  grass-leaved arrowhead  B
Senecio jacobaea (see note 3 below) tansy ragwort  B
Tamarix ramosissima saltcedar  B
Ulex europaeus gorse  B
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.  The wall subgenus species of hawkweed are not designated by the State Weed Board for control in King County. However, the species European hawkweed (Hieracium sabaudum) in the wall subgenus has been selected by the King County Weed Board for required control in all areas of King County.  All species of the meadow subgenus are designated by the State Weed Board for required control in King County.
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.

Regulated Class C noxious weeds
(control is required for these species in King County)

Scientific name Common name State class
Artemisia absinthium absinth wormwood  C
Solanum rostratum buffalobur  C

Non-regulated Class B and C noxious weeds
(Class B and C noxious weeds that are not designated for control in King County, control recommended but not required in King County)

Scientific name Common name State class
Ailanthus altissima (external link) tree-of-heaven  C
Arum italicum (external link) Italian arum  C
Berberis vulgaris (external link) common barberry   C
Buddleia davidii butterfly bush  B
Cirsium arvense Canada thistle  C
Cirsium vulgare bull thistle  C
Clematis vitalba old man's beard  C
Conium maculatum poison-hemlock  B
Convolvulus arvensis field bindweed  C
Cortaderia jubata (external link) jubata grass  C
Cortaderia selloana (external link) Pampas grass  C
Crataegus monogyna English hawthorn  C 
Cytisus scoparius (see note 3 below) Scotch broom  B
Daphne laureola spurge laurel  B
Daucus carota wild carrot  C
Dipsacus fullonum common teasel   C
Ficaria verna (external link) lesser celandine  B 
Foeniculum vulgare (external link)  common fennel (except bulbing variety azoricum)  B
Geranium robertianum herb Robert  B
Hedera helix Baltica English ivy  C
Hedera helix Pittsburgh English ivy  C
Hedera helix Star English ivy  C
Hedera hibernica Atlantic ivy  C
Hieracium, subgenus Hieracium (see note 4 below) hawkweeds: all non-native species and hybrids of the wall subgenus  B
Hypericum perforatum (see note 1 below) common St. Johnswort  C
Hypochaeris radicata (external link) common catsear   C
Iris pseudacorus yellow flag iris  C
Lamiastrum galeobdolon yellow archangel  B
Lepidium draba (external link) hoary cress  C
Lepidium appelianum (external link) hairy whitetop  C 
Leucanthemum vulgare oxeye daisy  C
Linaria vulgaris yellow toadflax  C
Myriophyllum spicatum Eurasian watermilfoil  B
Nymphaea odorata fragrant water lily  C
Phalaris arundinacea reed canarygrass  C
Polygonum x bohemicum (see note 2 below) Bohemian knotweed  B
Polygonum sachalinense (see note 2 below) giant knotweed  B
Polygonum polystachyum (see note 2 below) Himalayan knotweed  B
Polygonum cuspidatum (see note 2 below) Japanese knotweed  B
Potamogeton crispus (external link) curly-leaf pondweed  C
Rubus armeniacus Himalayan blackberry  C
Rubus laciniatus evergreen blackberry  C
Saccharum ravennae (external link) Ravenna grass   B
Senecio vulgaris (external link)  common groundsel  C
Soliva sessilis lawnweed  C
Sonchus arvensis ssp. arvensis perennial sowthistle  C
Tanacetum vulgare common tansy  C
1. Permit from KC Weed Board required to grow common St. Johnswort as a crop in King County.

2. Control of Bohemian, Japanese, giant and Himalayan knotweed is required on the Green River and its tributaries upstream of the Auburn City Limits and on the Cedar River and its tributaries upstream of the Renton City Limits (tributaries included are those defined as Type S, F or N aquatic areas in KCC 21A.24.355). Control of these invasive knotweed species is required up to the ordinary high water mark (or up to the top of the bank if the ordinary high water mark cannot be identified) and in the adjacent buffer area as specified in KCC 21A.24.358. This requirement to control knotweed is contingent upon the noxious weed program or program partners providing knotweed control services in the selected area for affected private landowners who request assistance.

3. Control of Scotch broom is required on the right-of-way of King County's section of SR-2 and on the I-90 right-of-way between mile marker 34 and the King/Kittitas county line.
4. 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.  The wall subgenus species of hawkweed are not designated by the State Weed Board for control in King County. However, the species European hawkweed (Hieracium sabaudum) in the wall subgenus has been selected by the King County Weed Board for required control in all areas of King County.  All species of the meadow subgenus are designated by the State Weed Board for required control in King County.

King County weeds of concern
(This list is for educational purposes only; these species are not classified as noxious weeds in Washington State. These species often impact and degrade native plant and animal habitat. Control is recommended where possible and new plantings are discouraged.)

Scientific name Common name State class
Aegopodium podagraria (external link) bishop's weed  NONE
Convolvulus sepium (external link)  hedge bindweed, morning glory  NONE
Ilex aquifolium English holly  NONE
Impatiens capensis (external link) spotted jewelweed  NONE
Prunus avium (external link) bird cherry  NONE
Prunus laurocerasus English laurel  NONE
Ranunculus acris tall buttercup  NONE
Ranunculus repens creeping buttercup  NONE
Robinia pseudoacacia (external link) black locust  NONE
Rosa multiflora multiflora rose  NONE
Solanum dulcamara bittersweet nightshade  NONE
Sorbus aucuparia (external link) European mountain-ash  NONE
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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).