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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:

RCW 17.10

WAC 16-750

Learn more about how the noxious weed classification system and listing process works in this blog written by Program specialists

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.

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 M. hippuroides A
No wild four o'clock Mirabilis nyctaginea A
View footnotes

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
View footnotes

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
View footnotes

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
View footnotes
Weeds of Concern

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

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 2022 list:

a. Additions to list: harlequin or Norway maple; introduced peavines

b. Additions to rules: shiny geranium selection defined in note 10

c. Common names to be changed to uniquely descriptive name or away from nationalist and/or exclusionary language: common or English holly


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;

g. Syrian bean-caper;

h. Vochin knapweed;

i. Oriental clematis;

j. Spanish broom;

k. South American spongeplant;

l. Turkish thistle;

m. Italian thistle;

n. Malta starthistle;

o. Italian arum


10. Control of shiny geranium is required is required at any elevation equal to or greater than 1000 feet within King County.


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