Noxious Weed Species

The lists of Colorado's Noxious Weeds are located in the below table. To view more about a specific weed click on the name in blue text. If a plant name does not have a link this is because a plant plan or assessment has not been completed. Noxious Weed List.

List A Species in Colorado that are designated by the Commissioner for eradication.

List B Species are species for which the Commissioner, in consultation with the state noxious weed advisory committee, local governments, and other interested parties, develops and implements state noxious weed management plans designed to stop the continued spread of these species.

List C Species are species for which the Commissioner, in consultation with the state noxious weed advisory committee, local governments, and other interested parties, will develop and implement state noxious weed management plans designed to support the efforts of local governing bodies to facilitate more effective integrated weed management on private and public lands. The goal of such plans will not be to stop the continued spread of these species but to provide additional education, research, and biological control resources to jurisdictions that choose to require management of List C species.

Watch List Species that have been determined to pose a potential threat to the agricultural productivity and environmental values of the lands of the state. The Watch List is intended to serve advisory and educational purposes only. Its purpose is to encourage the identification and reporting of these species to the Commissioner in order to facilitate the collection of information to assist the Commissioner in determining which species should be designated as noxious weeds. Printable Colorado Watch List.
 Download the noxious weed identification mobile app for IOS and Android

List A Species

Not Known In Colorado  |  Less Than 10 Known Populations  | More Than 10 Populations in Colorado

Not Known In Colorado


Alhagi pseudalhagi

Common crupina

Crupina vulgaris


Giant salvinia

Salvinia molesta


Hydrilla verticillata


Taeniatherum caput-medusae


Myriophyllum aquaticum

Squarrose knapweed

Centaurea virgata

Less Than 10 Known Populations

African rue

Peganum harmala

Dyer's woad
Isatis tinctoria

Elongated mustard

Brassica elongata

Flowering rush

Butomus umbellatus

Meadow knapweed

Centaurea x moncktonii

Rush skeletonweed

Chondrilla juncea

Tansy ragwort

Senecio jacobaea

Yellow starthistle

Centaurea solstitialis

More Than 10 Populations in Colorado

Cypress spurge

Euphorbia cyparissias

Giant reed

Arundo donax
Hairy willow-herb
Hairy willow-herb

Epilobium hirsutum


Japanese, Giant, and Bohemian

Mediterranean sage

Salvia aethiopis

Myrtle spurge

Euphorbia myrsinites

Orange hawkweed

Hieracium aurantiacum

Purple loosestrife

Lythrum salicaria

List B Species

Absinth wormwood

Artemisia absinthium

Black henbane

Hyoscyamus niger


Saponaria officinalis

Bull thistle

Cirsium vulgare

Canada thistle

Cirsium arvense

Chinese clematis

Clematis orientalis

Common tansy

Tanacetum vulgare

Common teasel

Dipsacus fullonum

Cutleaf teasel

Dipsacus laciniatus

Dalmatian toadflax

Linaria dalmatica & genistifolia

Dame's rocket

Hesperis matronalis

Diffuse knapweed

Centaurea diffusa

Eurasian watermilfoil

Myriophyllum spicatum

Hoary cress

Lepidium draba


Cynoglossum officinale

Hybrid knapweed

Centaurea x psammogena = C. stoebe x C. diffusa

Hybrid toadflax

Linaria vulgaris x L. dalmatica

Jointed goatgrass

Aegilops cylindrica

Leafy spurge

Euphorbia esula

Mayweed chamomile

Anthemis cotula

Moth mullein

Verbascum blattaria

Musk thistle

Carduus nutans

Oxeye daisy

Leucanthemum vulgare

Perennial pepperweed

Lepidium latifolium

Plumeless thistle

Carduus acanthoides

Russian knapweed

Acroptilon repens


Elaeagnus angustifolia

Salt cedar

Tamarix chinensis, T. parviflora, and  T. ramosissima

Scentless chamomile

Tripleurospermum inodorum

Scotch thistle

Onopordum acanthium

Spotted knapweed

Centaurea stoebe

Sulfur cinquefoil

Potentilla recta

Wild caraway

Carum carvi

Yellow nutsedge

Cyperus esculentus

Yellow toadflax

Linaria vulgaris

List C Species


Cichorium intybus

Common burdock

Arctium minus

Common mullein

Verbascum thapsus
Common St. Johnswort
Common St. Johnswort

Hypericum perforatum

Downy brome

Bromus tectorum

Field bindweed

Convolvulus arvensis


Halogeton glomeratus


Sorghum halepense

Perennial sowthistle

Sonchus arvensis

Poison hemlock

Conium maculatum


Tribulus terrestris


Elymus repens

Redstem filaree

Erodium cicutarium


Abutilon theophrasti

Wild-proso millet

Panicum miliaceum

Watch List Species

Baby's breath
Baby's breath

Gypsophila paniculata
Caucasian bluestem
Caucasian bluestem

Bothriochloa bladhii
Common bugloss
Common bugloss

Anchusa officinalis
Common reed
Common reed

Phragmites australis
Garlic mustard
Garlic mustard

Alliaria petiolata
Garden loosestrife
Garden loosestrife

Lysimachia vulgaris
Himalayan blackberry
Himalayan blackberry
Rubus armeniacus
Hoary Allysum
Hoary alyssum

Berteroa incana
Meadow hawkweed
Meadow hawkweed

Hieracium caespitosum

Asphodelus fistulosus
Siberian elm
Siberian elm
Ulmus pumila
Scotch broom
Scotch broom

Cytisus scoparius

Sphaerophysa salsula
Syrian beancaper
Syrian beancaper

Zygophyllum fabago

Tree of Heaven
Ailanthus altissima
Ventenata grass
Ventenata grass
Ventenata dubia
White bryony
White bryony

Bryonia alba
Yellow bluestem
Yellow bluestem
Bothriochloa ischaemum
Yellow flag iris
Yellow flag iris

Iris pseudacorus