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 |
|---|---|---|
| bean-caper8e(1) | Zygophyllum fabago | A |
| 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, short fringed8e(2) | Centaurea nigrescens | A |
| kudzu | Pueraria montana var. lobata | A |
| meadow clary | Salvia pratensis | A |
| orange peel clematis8e(3) | 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 |
| smooth frogbit8e(5) (external link) | Limnobium laevigatum | A |
| Spanish broom | Spartium junceum | A |
| Syrian bean-caper | Zygophyllum fabago | A |
| Texas blueweed | Helianthus ciliaris | A |
| thistle, ashen8e(6) (external link) | Carduus pycnocephalus | A |
| thistle, milk | Silybum marianum | A |
| thistle, shore8e(7) (external link) | Carduus cinereus | A |
| thistle, slenderflower |
Carduus tenuiflorus | 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 |
| Egeria1,9a |
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 subgenus2 | 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-hemlock7 (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, yellow | Centaurea solstitialis |
B |
| sulfur cinquefoil | Potentilla recta | B |
| tansy ragwort3 | Jacobaea vulgaris | B |
| thistle, musk | Carduus nutans | B |
| thistle, plumeless (external link) | Carduus acanthoides | B |
| thistle, Scotch | Onopordum acanthium | B |
| tocalote8e(8) (external link) |
Centaurea melitensis | B |
| velvetleaf | Abutilon theophrasti | B |
| water primrose | Ludwigia hexapetala | B |
| white bryony (external link) | Bryonia alba | B |
| wild basil8a (external link) | Clinopodium vulgare | B |
| wild chervil |
Anthriscus sylvestris | B |
| yellow floating heart | Nymphoides peltata | B |
| yellow nutsedge | Cyperus esculentus | B |
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 davidii7c | 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 hawthorn9b |
Crataegus monogyna | C |
| common St. Johnswort1 | Hypericum perforatum | C |
| common tansy8b | Tanacetum vulgare | B |
| 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 |
| green alkanet8a (external link) | Pentaglottis sempervirens | C |
| hairy whitetop (external link) | Lepidium appelianum | C |
| hanging sedge5,8a,d (external link) | Carex pendula (ssp. pendula and ssp. agastachys) | B |
| hawkweeds; all non-native species and hybrids of the wall subgenus except European hawkweed4 | Hieracium, subgenus Hieracium (except Hieracium sabaudum) | B |
| herb Robert | Geranium robertianum | B |
| hoary cress (external link) | Lepidium draba | 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, hybrid5,9c |
Fallopia x bohemica | B |
| knotweed, giant5 | Fallopia sachalinensis | B |
| knotweed, Himalayan5 | Persicaria wallichii | B |
| knotweed, itadori5,9d | Fallopia japonica | B |
| lesser celandine (external link) | Ficaria verna | B |
| old man's beard | Clematis vitalba | C |
| orange candleflower8e(9) (external link) |
Arum italicum | 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 |
| rough chervil5,8a,8d | Chaerophyllum temulum | B |
| scentless mayweed (external link) | Tripleurospermum inodorum |
C |
| Scotch broom6 | 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, creeping9e | 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 (excluding ssp. sativus)8c | C |
| yellow archangel | Lamiastrum galeobdolon8c | B |
| yellow flag iris | Iris pseudacorus | C |
| yellow toadflax | Linaria vulgaris | C |
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 |
|---|---|---|
| bindweed, nonnative species and hybrids (does not include native hedge bindweed)8c | Calystegia silvatica ssp. disjuncta C. xlucana | NONE |
| 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 |
| bur chervil8a (external link) | Anthriscus caucalis | 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 |
| horse-chestnut | Aesculus hippocastanum | NONE |
| multiflora rose | Rosa multiflora | NONE |
| rough chervil |
Chaerophyllum temulum | NONE |
| silver lace vine |
Fallopia baldschuanica (syn. Polygonum aubertii) | NONE |
| vested blackberry8a (external link) | Rubus vestitus | NONE |
|
Notes: |
||
| 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) are consolidated into two Class B listings by subgenus - meadow (Pilosella) and wall (Hieracium). All species of the meadow subgenus are designated by the State Weed Board for required control in King County. The species European hawkweed (Hieracium sabaudum) in the wall hawkweed subgenus has been selected by the King County Weed Board for required control throughout King County. Control of all other species in the wall hawkweed subgenus is not required 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. | ||
| 4. Permit from KC Weed Board required to grow common St. Johnswort as a crop in King County. | ||
| 5. Control of rough chervil; hanging sedge; 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. | ||
| 6. 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. | ||
| 7. Control of poison hemlock is required on all public lands and public rights-of-way within King County. | ||
| 8. Change indicated from 2021 list:
a. Additions to list: wild basil; hanging sedge; rough chervil; green alkanet; bur chervil; vested blackberry b. Updated weed class: common tansy c. Taxonomic update or clarifying definition: Buddleja davidii botanical name update; Daucus carota (exluding ssp. sativus) culinary variety exclusion; Lamisastrum galeabdolon is outdated name but still in use (Lamium galeobdolon is correct name); Hedge bindweed species were recently differentiated between native and nonnative varieties in local herbaria d. Additions to rules: rough chervil and hanging sedge added to note 5 above e. Common names to be changed to uniquely descriptive name or away from nationalist and/or exclusionary language: Syrian bean-caper1; Vochin knapweed2; Oriental clematis3; Spanish broom4; South American spongeplant5; Turkish thistle6; Italian thistle7; Malta starthistle8; Italian arum9 |
||
| 9. Previous common name changes (within the last 3 years): a. Brazilian elodea; b. English hawthorn; c. Bohemian knotweed; d. Japanese knotweed; e. Canada thistle; f. English laurel | ||
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).