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King County noxious weeds list
The King County Noxious Weed Control Board has adopted this Noxious Weed List based on these state laws:
About the noxious weeds list
Find noxious weeds using the tables below. The tables organize weeds by class and lists entries alphabetically. There are tabs for scientific and common names. The superscript numbers refer to additional notes, which are listed at the bottom of each tab.
For the "In King County" column:
Yes: Known to occur in King County.
Historically: Historically present but thought to be eradicated.
No: Not present in King County.Go to any weed class by selecting a designation:
- Class A noxious weeds
- Class B noxious weeds
- Class C noxious weeds
- Non-Regulated noxious weeds
- Weeds of concern
- Footnotes
Tables display noxious weeds alphabetically (A-Z) by Common name by default. To re-order species by any other category click on the appropriate table heading (i.e. Scientific name), click again to reverse the order (Z-A).
Regulated Class A weeds
State law requires property owners to eradicate all Class A species due to potential threat and limited distribution.
| In King County |
Common name |
Scientific name |
Class |
|---|---|---|---|
| No | bean-caper2 | Zygophyllum fabago | A |
| Yes | common crupina | Crupina vulgaris | A |
| Historically | cordgrass, common | Spartina anglica | A |
| No | cordgrass, dense flowered | Spartina densiflora | A |
| No | cordgrass, salt meadow | Spartina patens | A |
| No | cordgrass, smooth | Spartina alterniflora | A |
| No | dyers woad | Isatis tinctoria | A |
| Yes | eggleaf spurge | Euphorbia oblongata | A |
| Yes | false brome | Brachypodium sylvaticum | A |
| Yes | floating primrose-willow | Ludwigia peploides | A |
| No | flowering rush | Butomus umbellatus | A |
| Yes | garlic mustard | Alliaria petiolata | A |
| Yes | giant hogweed | Heracleum mantegazzianum | A |
| Yes | goatsrue | Galega officinalis | A |
| Historically | hydrilla | Hydrilla verticillata | A |
| No | Johnsongrass | Sorghum halepense | A |
| Yes | knapweed, bighead | Centaurea macrocephala | A |
| No | knapweed, short fringed2 | Centaurea nigrescens | A |
| No | kudzu | Pueraria montana var. lobata | A |
| Yes | meadow clary | Salvia pratensis | A |
| No | orange peel clematis2 | Clematis orientalis | A |
| No | purple starthistle | Centaurea calcitrapa | A |
| Yes | reed sweetgrass | Glyceria maxima | A |
| Yes | ricefield bulrush | Schoenoplectus mucronatus | A |
| Yes | roundleaf bittersweet3a | Celastrus orbiculatus | A |
| Yes | rush broom2 | Spartium junceum | A |
| Yes | sage, clary | Salvia sclarea | A |
| No | sage, Mediterranean | Salvia aethiopis | A |
| Yes | silverleaf nightshade | Solanum elaeagnifolium | A |
| Yes | small-flowered jewelweed | Impatiens parviflora | A |
| Yes | smooth frogbit2 | Limnobium laevigatum | A |
| Yes | soft broom2 | Genista monspessulana | A |
| No | Texas blueweed | Helianthus ciliaris | A |
| No | thistle, ashen2 | Carduus cinereus | A |
| No | thistle, marsh3a | Carduus palustre | A |
| Yes | thistle, milk | Silybum marianum | A |
| No | thistle, shore2 | Carduus pycnocephalus | A |
| No | thistle, slenderflower | Carduus tenuiflorus | A |
| No | variable leaf milfoil and hybrids | Myriophyllum heterophyllum and M. heterophyllum x M. hippuroides | A |
| No | wild four o'clock | Mirabilis nyctaginea | A |
Regulated Class B weeds
Regulated in counties where they are limited in distribution or a local priority. The following Class B weeds have been designated by the State Weed Board or selected by the King County Weed Board. Property owners in King County are required to control these species.
| In King County |
Common name |
Scientific name |
Class |
|---|---|---|---|
| Yes | blueweed; viper's bugloss | Echium vulgare | B-Regulated |
| Yes | bugloss, annual | Lycopsis arvensis | B-Regulated |
| Yes | bugloss, common | Anchusa officinalis | B-Regulated |
| No | camelthorn | Alhagi maurorum | B-Regulated |
| Yes | common reed (non-native genotypes) | Phragmites australis | B-Regulated |
| Yes | Dalmatian toadflax | Linaria dalmatica ssp. dalmatica | B-Regulated |
| Yes | Egeria1a | Egeria densa | B-Regulated |
| No | fanwort | Cabomba caroliniana | B-Regulated |
| Yes | gorse | Ulex europaeus | B-Regulated |
| No | grass-leaved arrowhead | Sagittaria graminea | B-Regulated |
| Yes | hairy willowherb | Epilobium hirsutum | B-Regulated |
| No | hardheads2 | Rhaponticum repens | B-Regulated |
| Yes | meadow hawkweeds: all non-native species and hybrids of the meadow subgenus | Hieracium, subgenus Pilosella | B-Regulated |
| Yes | hawkweed, autumn2 | Hieracium sabaudum | B-Regulated |
| Yes | hawkweed, orange | Hieracium aurantiacum | B-Regulated |
| No | hawkweed oxtongue | Picris hieracioides | B-Regulated |
| Yes | hoary alyssum | Berteroa incana | B-Regulated |
| Yes | houndstongue | Cynoglossum officinale | B-Regulated |
| No | indigobush | Amorpha fruticosa | B-Regulated |
| No | knapweed, black | Centaurea nigra | B-Regulated |
| Yes | knapweed, brown | Centaurea jacea | B-Regulated |
| Yes | knapweed, diffuse | Centaurea diffusa | B-Regulated |
| Yes | knapweed, meadow | Centaurea x gerstlaueri | B-Regulated |
| Yes | knapweed, spotted | Centaurea stoebe | B-Regulated |
| Yes | kochia | Bassia scoparia | B-Regulated |
| Yes | loosestrife, garden | Lysimachia vulgaris | B-Regulated |
| Yes | loosestrife, purple | Lythrum salicaria | B-Regulated |
| Yes | parrotfeather | Myriophyllum aquaticum | B-Regulated |
| Yes | perennial pepperweed | Lepidium latifolium | B-Regulated |
| Yes | policeman's helmet | Impatiens glandulifera | B-Regulated |
| Yes | rush skeletonweed | Chondrilla juncea | B-Regulated |
| Yes | saltcedar | Tamarix ramosissima | B-Regulated |
| Yes | spurge, leafy | Euphorbia virgata | B-Regulated |
| Yes | starthistle, yellow | Centaurea solstitialis | B-Regulated |
| Yes | sulfur cinquefoil | Potentilla recta | B-Regulated |
| Yes | tansy ragwort | Jacobaea vulgaris | B-Regulated |
| Yes | thistle, cotton2 | Onopordum acanthium | B-Regulated |
| Yes | thistle, musk | Carduus nutans | B-Regulated |
| Yes | thistle, plumeless | Carduus acanthoides | B-Regulated |
| No | tocalote2 | Centaurea melitensis | B-Regulated |
| Yes | tussilago2 | Tussilago farfara | B-Regulated |
| Yes | velvetleaf | Abutilon theophrasti | B-Regulated |
| Historically | water primrose | Ludwigia hexapetala | B-Regulated |
| Yes | white bryony | Bryonia alba | B-Regulated |
| Yes | wild basil | Clinopodium vulgare | B-Regulated |
| Yes | wild chervil | Anthriscus sylvestris | B-Regulated |
| Yes | yellow floating heart | Nymphoides peltata | B-Regulated |
| Yes | yellow nutsedge | Cyperus esculentus | B-Regulated |
Regulated Class C weeds
The following Class C weeds have been selected by the King County Weed Board based on potential threat and feasibility of control. Property owners in King County are required to control these species.
| In King County |
Common name |
Scientific name |
Class |
|---|---|---|---|
| Yes | absinth wormwood |
Artemisia absinthium |
C-Regulated |
| Yes | beachgrasses (marram) & their hybrid | Ammophila arenaria, A. breviligulata, and A. arenaria x breviligulata | C-Regulated |
Non-regulated noxious weeds
Property owners in King County are not required to control the following Class B and C weeds, but control is recommended where feasible due to their impacts. Species that are classified with "selective" require control within specific geographical parameters. See footnotes for details.
| In King County |
Common name |
Scientific name |
Class |
|---|---|---|---|
| Yes | blackberry, cutleaf2 | Rubus laciniatus | C-Non-Regulated |
| Yes | blackberry, Himalayan | Rubus bifrons | C-Non-Regulated |
| Yes | buffalobur |
Solanum rostratum |
C-Non-Regulated |
| Yes | butterfly bush | Buddleja davidii | B-Non-Regulated |
| Yes | cattail, nonnative species and hybrids | Typha angustifolia, T. domingensis, and T. x glauca (and any other nonnative Typha spp.) | C-Non-Regulated |
| No | common barberry | Berberis vulgaris | C-Non-Regulated |
| Yes | common catsear | Hypochaeris radicata | C-Non-Regulated |
| Yes | common fennel | Foeniculum vulgare (excluding F. vulgare var. azoricum) | B-Non-Regulated |
| Yes | common groundsel | Senecio vulgaris | C-Non-Regulated |
| Yes | common hawthorn | Crataegus monogyna | C-Non-Regulated |
| Yes | common St. Johnswort1b | Hypericum perforatum | C-Non-Regulated |
| Yes | common tansy | Tanacetum vulgare | B-Non-Regulated |
| Yes | common teasel | Dipsacus fullonum | C-Non-Regulated |
| Yes | curly leaf pondweed | Potamogeton crispus | C-Non-Regulated |
| Yes | field bindweed | Convolvulus arvensis | C-Non-Regulated |
| Yes | fragrant water lily | Nymphaea odorata | C-Non-Regulated |
| Yes | green alkanet | Pentaglottis sempervirens | C-Non-Regulated |
| Yes | hairy whitetop | Lepidium appelianum | C-Non-Regulated |
| Yes | hanging sedge1d | Carex pendula (ssp. pendula and ssp. agastachys) | B-Selective |
| Yes | hawkweeds, wall; all non-native species and hybrids of the wall subgenus except autumn hawkweed | Hieracium, subgenus Hieracium (except Hieracium sabaudum) | B-Non-Regulated |
| Yes | herb Robert | Geranium robertianum | B-Non-Regulated |
| Yes | hoary cress | Lepidium draba | C-Non-Regulated |
| Yes | ivy, Atlantic | Hedera hibernica | C-Non-Regulated |
| Yes | ivy, common2 | Hedera helix 'Baltica', Hedera helix 'Pittsburgh', Hedera helix 'Star' | C-Non-Regulated |
| Yes | jubata grass | Cortaderia jubata | C-Non-Regulated |
| Yes | knotweed, garden1d, 2 | Persicaria wallichii |
B-Selective |
| Yes | knotweed, giant1d | Fallopia sachalinensis | B-Selective |
| Yes | knotweed, hybrid1d |
Fallopia x bohemica |
B-Selective |
| Yes | knotweed, itadori1d | Fallopia japonica | B-Selective |
| Yes | lesser celandine | Ficaria verna | B-Non-Regulated |
| Yes | myrtle spurge | Euphorbia myrsinites | B-Non-Regulated |
| Yes | old man's beard | Clematis vitalba | C-Non-Regulated |
| Yes | orange candleflower2 | Arum italicum | C-Non-Regulated |
| Yes | oxeye daisy | Leucanthemum vulgare | C-Non-Regulated |
| Yes | Pampas grass | Cortaderia selloana | C-Non-Regulated |
| Yes | poison hemlock1c | Conium maculatum | B-Selective |
| No | Ravenna grass | Tripidium ravennae | B-Non-Regulated |
| Yes | reed canarygrass | Phalaris arundinacea | C-Non-Regulated |
| Yes | rough chervil1d | Chaerophyllum temulum | B-Selective |
| Yes | scentless mayweed | Tripleurospermum inodorum | C-Non-Regulated |
| Yes | Scotch broom1e | Cytisus scoparius | B-Selective |
| Yes | shiny geranium1f | Geranium lucidum | B-Selective |
| Yes | spiny cocklebur | Xanthium spinosum |
C-Non-Regulated |
| Yes | spiked watermilfoil | Myriophyllum spicatum | B-Non-Regulated |
| No | spiked watermilfoil hybrid | Myriophyllum spicatum x M. sibiricum | C-Non-Regulated |
| Yes | spotted jewelweed | Impatiens capensis | C-Non-Regulated |
| Yes | spurge laurel | Daphne laureola | B-Non-Regulated |
| Yes | thistle, bull | Cirsium vulgare | C-Non-Regulated |
| Yes | thistle, creeping | Cirsium arvense | C-Non-Regulated |
| Yes | tree-of-heaven | Ailanthus altissima | C-Non-Regulated |
| Yes | ventenata | Ventenata dubia | C-Non-Regulated |
| Yes | white cockle | Silene latifolia | C-Non-Regulated |
| Yes | wild carrot | Daucus carota (excluding ssp. sativus) | C-Non-Regulated |
| Yes | yellow archangel | Lamium galeobdolon | B-Non-Regulated |
| Yes | yellow flag iris | Iris pseudacorus | C-Non-Regulated |
| Yes | yellow toadflax | Linaria vulgaris | C-Non-Regulated |
Weeds of concern
The King County Weed Board also encourages control of non-native, invasive plants that are not on the state noxious weed list but have impacts in King County. Plants on this list are considered Invasive Vegetation in King County’s Critical Areas Ordinance (KCC 21A.06.641C). Property owners are not required to control these plants. Education is being provided as authorized by RCW 17.10.090.
| In King County |
Common name |
Scientific name |
Category |
|---|---|---|---|
| Yes | bindweed, large/hybrid | Calystegia x lucana | Weed of Concern |
| Yes | bird cherry | Prunus avium | Weed of Concern |
| Yes | bird's-foot trefoil | Lotus corniculatus | Weed of Concern |
| Yes | bishop's weed | Aegopodium podagraria | Weed of Concern |
| Yes | bittersweet nightshade | Solanum dulcamara | Weed of Concern |
| Yes | black locust | Robinia pseudoacacia | Weed of Concern |
| Yes | bur chervil | Anthriscus caucalis | Weed of Concern |
| Yes | buttercup, creeping | Ranunculus repens | Weed of Concern |
| Yes | buttercup, tall | Ranunculus acris | Weed of Concern |
| Yes | cherry laurel | Prunus laurocerasus | Weed of Concern |
| Yes | common holly2 | Ilex aquifolium | Weed of Concern |
| Yes | European mountain-ash | Sorbus aucuparia | Weed of Concern |
| Yes | harlequin maple; Norway maple | Acer platanoides | Weed of Concern |
| Yes | horse chestnut | Aesculus hippocastanum | Weed of Concern |
| Yes | introduced peavines | Lathyrus sylvestris, L. latifolius | Weed of Concern |
| Yes | multiflora rose | Rosa multiflora | Weed of Concern |
| Yes | silver lace vine | Fallopia baldschuanica (syn. Polygonum aubertii) | Weed of Concern |
| Yes | vested blackberry | Rubus vestitus | Weed of Concern |
Footnotes
1. County level specifications (not statewide - regulations specific to King County)
a. Egeria: control required throughout King County except in Green Lake, Lake Washington, Lake Sammamish, Lake Union, Lake Fenwick, Lake Doloff and the Sammamish River.
b. Common St. Johnswort: permit from KC Weed Board required to grow as a crop in King County.
c. Poison hemlock: control required on all public lands and public and railroad rights-of-way within King County.
d. Rough chervil; hanging sedge; hybrid, itadori, giant, and garden knotweeds: control required up to the ordinary high-water mark 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. 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.
e. Scotch broom: control 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.
f. Shiny geranium: control required at any elevation equal to or greater than 1000 feet within King County.
2. Listed common names changed within the last 4 years
| NEW Common Name (A-Z) | OLD Common Name | Scientific Name |
|---|---|---|
| ashen thistle | Turkish thistle | Carduus cinereus |
| autumn hawkweed | European hawkweed | Hieracium sabaudum |
| bean-caper | Syrian bean-caper | Zygophyllum fabago |
| common holly | English holly | Ilex aquifolium |
| common ivy | English ivy | Hedera helix ssp. |
| cotton thistle | Scotch thistle | Onopordum acanthium |
| cutleaf blackberry | evergreen blackberry | Rubus lacinatus |
| garden knotweed | Himalayan knotweed | Persicaria wallichii |
| hardheads | Russian knapweed | Rhaponticum repens |
| orange candleflower | Italian arum | Arum italicum |
| orange peel clematis | Oriental clematis | Clematis orientalis |
| rush broom | Spanish broom | Spartium junceum |
| shore thistle | Italian thistle | Carduus pycnocephalus |
| short-fringed knapweed | vochin knapweed | Centaurea nigrescens |
| smooth frogbit | South American spongeplant | Limnobium laevigatum |
| soft broom | French broom | Genista monspessulana |
| spiked watermilfoil | Eurasian watermilfoil | Myriophyllum spicatum |
| tocalote | Malta starthistle | Centaurea melitensis |
| tussilago |
European coltsfoot |
Tussilago farfara |
3. Change for 2025 list
a. Required additions from state list: roundleaf bittersweet & marsh thistle