King County Noxious Weed List
- Class A noxious weeds
- Class B noxious weeds
- Class C noxious weeds
- Non-regulated noxious weeds
- Weeds of concern
Regulated Class A noxious weeds
(eradication required throughout Washington State including King County)
| Common name | Scientific name | State class |
|---|---|---|
| common crupina | Crupina vulgaris | A |
| cordgrass, common | Spartina anglica | A |
| cordgrass, dense flower (external link) | Spartina densiflora | A |
| cordgrass, salt meadow | Spartina patens | A |
| cordgrass, smooth | Spartina alterniflora | A |
| dyers woad | Isatis tinctoria | A |
| eggleaf spurge (external link) | Euphorbia oblongata | A |
| false brome | Brachypodium sylvaticum | A |
| floating primrose-willow | Ludwigia peploides | A |
| flowering-rush | Butomus umbellatus | A |
| French broom | Genista monspessulana | A |
| garlic mustard | Alliaria petiolata | A |
| giant hogweed | Heracleum mantegazzianum | A |
| goatsrue | Galega officinalis | A |
| hydrilla | Hydrilla verticillata | A |
| Johnsongrass (external link) | Sorghum halepense | A |
| knapweed, bighead | Centaurea macrocephala | A |
| knapweed, Vochin | Centaurea nigrescens | A |
| kudzu | Pueraria montana var. lobata | A |
| meadow clary | Salvia pratensis | A |
| oriental clematis | Clematis orientalis | A |
| purple starthistle | Centaurea calcitrapa | A |
| reed sweetgrass | Glyceria maxima | A |
| ricefield bulrush (external link) | Schoenoplectus mucronatus | A |
| sage, clary | Salvia sclarea | A |
| sage, Mediterranean | Salvia aethiopis | A |
| silverleaf nightshade (external link) | Solanum elaeagnifolium | A |
| small-flowered jewelweed | Impatiens parviflora | A |
| South American spongeplant (external link) | Limnobium laevigatum | A |
| Spanish broom | Spartium junceum | A |
| Syrian bean-caper | Zygophyllum fabago | A |
| Texas blueweed | Helianthus ciliaris | A |
| thistle, Italian (external link) | Carduus pycnocephalus | A |
| thistle, milk | Silybum marianum | A |
| thistle, slenderflower | Carduus tenuiflorus | A |
| thistle, Turkish (external link) | Carduus cinereus | A |
| variable-leaf milfoil | Myriophyllum heterophyllum | A |
| wild four o'clock (external link) | Mirabilis nyctaginea | A |
Regulated Class B noxious weeds
(control is required for these species in King County)
| Common name | Scientific name | State class |
|---|---|---|
| blueweed; viper's bugloss (external link) | Echium vulgare | B |
| bugloss, annual | Lycopus arvensis | B |
| bugloss, common | Anchusa officinalis | B |
| camelthorn (external link) | Alhagi maurorum | B |
| common reed (non-native genotypes) | Phragmites australis | B |
| Dalmatian toadflax | Linaria dalmatica ssp. dalmatica | B |
| Egeria; Brazilian elodea (see note 1 below) |
Egeria densa | B |
| Tussilago farfara | B | |
| fanwort | Cabomba caroliniana | B |
| gorse | Ulex europaeus | B |
| grass-leaved arrowhead (external link) | Sagittaria graminea | B |
| hairy willowherb | Epilobium hirsutum | B |
| hawkweeds: all non-native species and hybrids of the meadow subgenus (see note 2 below) | Hieracium, subgenus Pilosella | B |
| hawkweed, European | Hieracium sabaudum | B |
| hawkweed, orange | Hieracium aurantiacum | B |
| hawkweed oxtongue (external link) | Picris hieracioides | B |
| hoary alyssum (external link) | Berteroa incana | B |
| houndstongue | Cynoglossum officinale | B |
| indigobush (external link) | Amorpha fruticosa | B |
| knapweed, black | Centaurea nigra | B |
| knapweed, brown | Centaurea jacea | B |
| knapweed, diffuse | Centaurea diffusa | B |
| knapweed, meadow | Centaurea x gerstlaueri | B |
| knapweed, Russian | Rhaponticum repens | B |
| knapweed, spotted | Centaurea stoebe | B |
| kochia | Bassia scoparia | B |
| loosestrife, garden | Lysimachia vulgaris | B |
| loosestrife, purple | Lythrum salicaria | B |
| parrotfeather | Myriophyllum aquaticum | B |
| perennial pepperweed | Lepidium latifolium | B |
| poison-hemlock (on public lands and public rights-of-way) | Conium maculatum | B |
| policeman's helmet | Impatiens glandulifera | B |
| rush skeletonweed | Chondrilla juncea | B |
| saltcedar | Tamarix ramosissima | B |
| shiny geranium | Geranium lucidum | B |
| spurge, leafy | Euphorbia virgata | B |
| starthistle, Malta | Centaurea melitensis | B |
| starthistle, yellow | Centaurea solstitialis |
B |
| sulfur cinquefoil | Potentilla recta | B |
| tansy ragwort (see note 3 below) | Jacobaea vulgaris | B |
| thistle, musk | Carduus nutans | B |
| thistle, plumeless (external link) | Carduus acanthoides | B |
| thistle, Scotch | Onopordum acanthium | B |
| velvetleaf | Abutilon theophrasti | B |
| water primrose | Ludwigia hexapetala | B |
| white bryony (external link) | Bryonia alba | B |
| wild chervil |
Anthriscus sylvestris | B |
| yellow floating heart | Nymphoides peltata | B |
| yellow nutsedge | Cyperus esculentus | B |
| 1. Egeria 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)
| Common name | Scientific name | State class |
|---|---|---|
| absinth wormwood | Artemisia absinthium | C |
| buffalobur | Solanum rostratum | 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)
| Common name | Scientific name | State class |
|---|---|---|
| blackberry, evergreen |
Rubus laciniatus | C |
| blackberry, Himalayan | Rubus bifrons or Rubus armeniacus | C |
| butterfly bush | Buddleia davidii | B |
| common barberry (external link) | Berberis vulgaris | C |
| common catsear (external link) | Hypochaeris radicata | C |
| common fennel (except bulbing variety azoricum) (external link) | Foeniculum vulgare | B |
| common groundsel (external link) | Senecio vulgaris | C |
| common hawthorn |
Crataegus monogyna | C |
| common St. Johnswort (see note 1 below) | Hypericum perforatum | C |
| common tansy | Tanacetum vulgare | C |
| common teasel | Dipsacus fullonum | C |
| curly-leaf pondweed (external link) | Potamogeton crispus | C |
| Eurasian watermilfoil | Myriophyllum spicatum | B |
| Eurasian watermilfoil hybrid (external link) | Myriophyllum spicatum x. M. sibiricum | C |
| field bindweed | Convolvulus arvensis | C |
| fragrant water lily | Nymphaea odorata | C |
| hairy whitetop (external link) | Lepidium appelianum | C |
| hawkweeds; all non-native species and hybrids of the wall subgenus except European hawkweed (see note 4 below) | Hieracium, subgenus Hieracium (except Hieracium sabaudum) | B |
| herb Robert | Geranium robertianum | B |
| hoary cress (external link) | Lepidium draba | C |
| Italian arum (external link) | Arum italicum | C |
| ivy, Atlantic | Hedera hibernica | C |
| ivy, English | Hedera helix 'Baltica', Hedera helix 'Pittsburgh', Hedera helix 'Star' | C |
| jubata grass (external link) | Cortaderia jubata | C |
|
knotweed, hybrid; Bohemian (see note 2 below) |
Fallopia x bohemica | B |
| knotweed, giant (see note 2 below) | Fallopia sachalinensis | B |
| knotweed, Himalayan (see note 2 below) | Persicaria wallichii | B |
| knotweed, itadori; Japanese (see note 2 below) | Fallopia japonica | B |
| lesser celandine (external link) | Ficaria verna | B |
| old man's beard | Clematis vitalba | C |
| oxeye daisy | Leucanthemum vulgare | C |
| nonnative cattail species and hybrids (does not include native species common cattail) (external link) |
Typha angustifolia, T. domingensis, and T. x glauca (and any other nonnative Typha spp.) (does not include native cattail T. latifolia) |
C |
| Pampas grass (external link) | Cortaderia selloana | C |
| perennial sowthistle | Sonchus arvensis ssp. arvensis | C |
| Ravenna grass (external link) | Tripidium ravennae | B |
| reed canarygrass | Phalaris arundinacea | C |
| scentless mayweed (external link) | Tripleurospermum inodorum |
C |
| Scotch broom (see note 3 below) | Cytisus scoparius | B |
| spiny cocklebur (external link) | Xanthium spinosum | C |
| spotted jewelweed (external link) | Impatiens capensis | C |
| spurge laurel | Daphne laureola | B |
| thistle, bull | Cirsium vulgare | C |
| thistle, creeping; Canada | Cirsium arvense | C |
| tree-of-heaven (external link) | Ailanthus altissima | C |
| ventenata (external link) | Ventenata dubia | C |
| white cockle (external link) | Silene latifolia | C |
| wild carrot | Daucus carota | C |
| yellow archangel | Lamiastrum galeobdolon | B |
| yellow flag iris | Iris pseudacorus | C |
| yellow toadflax | Linaria vulgaris | C |
| 1. Permit from KC Weed Board required to grow common St. Johnswort as a crop in King County. | ||
| 2. Control of hybrid, itadori, 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.)
| Common name | Scientific name | State class |
|---|---|---|
| bird cherry | Prunus avium | NONE |
| bird's-foot trefoil | Lotus corniculatus | NONE |
| bishop's weed | Aegopodium podagraria | NONE |
| bittersweet nightshade | Solanum dulcamara | NONE |
| black locust | Robinia pseudoacacia | NONE |
| buttercup, creeping | Ranunculus repens | NONE |
| buttercup, tall | Ranunculus acris | NONE |
| cherry laurel |
Prunus laurocerasus | NONE |
| English holly | Ilex aquifolium | NONE |
| European mountain-ash | Sorbus aucuparia | NONE |
| hanging sedge | Carex pendula | NONE |
| hedge bindweed, morning glory | Convolvulus sepium | NONE |
| horse-chestnut | Aesculus hippocastanum | NONE |
| multiflora rose | Rosa multiflora | NONE |
| rough chervil |
Chaerophyllum temulum | NONE |
| silver lace vine |
Fallopia baldschuanica (syn. Polygonum aubertii) | NONE |
Download Brochure
- 2021 King County Noxious Weed List Brochure (pdf)
- 2021 King County Noxious Weed List Simple Format (pdf)
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).