Whitman County
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Colfax, 99111

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Washington State Noxious Weed List
Class C Weeds

Each species is already widely established in Washington or is of special interest to the state's agricultural industry. Placement on the state noxious weed list allows counties to enforce control if locally desired. Other counties may choose simply to provide education or technical consultation to county residents. Canada thistle, a Class C noxious weed, illustrated the desirability of a law that provides local flexibility. This species is widely established in Washington, and most counties prefer to provide technical consultation to landowners on methods of suppression and control. Enforcement of control is the preferred policy, however, in those counties which have crops grown for certified seed.

Scientific Name

Common Name

Washington State Noxious Weed List - Class C Weeds

Common Name

Scientific Name

Common Name

Scientific Name


Gypsophila paniculata

old man's beard

Clematis vitalba

bindweed, field

Convolvulus arvensis


Conium maculatum

canarygrass, reed

Phalaris arundinacea

Common Reed (non native genotypes) 

Phragmites australis

cockle, white

Silene latifolia ssp. alba

rye, cereal

Secale cereale

cocklebur, spiny

Xanthium spinosum


Hemizonia pungens

cress, hoary

Cardaria draba

St. Johnswort, common

Hypericum perforatum


Cuscuta approximata

tansy, common

Tanacetum vulgare

goatgrass, jointed

Aegilops cylindrica

thistle, bull

Cirsium vulgare

Groundsel, common

Senecio vulgaris

thistle, Canada

Cirsium arvense

hawkweed, spp*

Non-Native hieracium

species except those listed as class A or B

toadflax, Yellow

Linaria vulgaris

henbane, black

Hyoscyamus niger

Willowherb, hairy

Epilobium hirsutum

iris, yellow flag

Iris pseudocorus

wormwood, absinth

Artemisia absinthium

ivy, English

*4 Cultivars only

Hedera hibernica 'Hibernica'

Hedera helix 'Baltica'

Hedera helix 'Pittsburgh'

Hedera helix  'Star'

Mayweed, scentless

Matricaria perforata

Knotweed bohemian

Polygonum Bohemicum

Butterfly Bush
Buddleia davidii

Curly-leaf pondweed


Potamogeton crispus



Pictures for many of these weeds may be found at Washington State Noxious Weed Board's website.
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