Saturday March 2, Red Flag Warning. No Open Burning in Boulder County

Noxious Weeds Identification
Cypress spurge (Euphorbia cyparissias), a noxious weed in Colorado.

The Boulder County Community Planning & Permitting office at 2045 13th St., Boulder is open to the public on Monday, Wednesday, and Thursday from 8 a.m. to 3 p.m., and on Tuesday from 10 a.m. to 3 p.m. Appointments are available on Tuesday but are not required. Schedule an appointment.

Identification of Noxious Weeds

Noxious weeds are plants that are not native to the county. Most have come from Europe or Asia either accidentally or as ornamentals that have escaped. These plants have an advantage because the insects, diseases, and animals that would normally control them are not found here. Because these plants have developed specialized mechanisms to survive, they are able to spread at an alarming rate.

List A weeds are rare weed species that are subject to eradication wherever detected in order to protect neighboring lands and the state as a whole.

Less Than 10 Known Species in Boulder County

Cypress spurge
Cypress spurge
Euphorbia cyparissias

Dyer's woad
Dyer’s woad
Isatis tinctoria

Giant reed
Giant reed
Arundo donax

Rush skeletonweed
Rush skeletonweed
Chondrilla juncea

More Than 10 Known Populations in Boulder County

Hairy willow-herb
Hairy willow-herb
Epilobium hirsutum

Knotweeds
Knotweeds
Japanese, Giant, and Bohemian

Myrtle spurge
Myrtle spurge
Euphorbia myrsinites

Mediterranean sage
Mediterranean sage
Salvia aethiopis

Orange hawkweed
Orange hawkweed
Hieracium aurantiacum

Purple loosestrife
Purple loosestrife
Lythrum salicaria

Not Known in Boulder County

African rue
African rue
Peganum harmala

Camelthorn
Camelthorn
Alhagi pseudalhagi

Hydrilla
Hydrilla
Hydrilla verticillata

Common crupina
Common crupina
Crupina vulgaris

Giant salvinia
Elongated mustard
Brassica elongata

Flowering rush
Flowering rush
Butomus umbellatus

Giant salvinia
Giant salvinia
Salvinia molesta

Meadow knapweed
Meadow knapweed
Centaurea pratensis

Medusahead
Medusahead
Taeniatherum caput-medusae

Parrotfeather
Parrotfeather
Myriophyllum aquaticum

Squarrose knapweed
Squarrose knapweed
Centaurea virgata

Tansy ragwort
Tansy ragwort
Senecio jacobaea

Yellow starthistle
Yellow starthistle
Centaurea solstitialis

Eradicated from Boulder County 2012. Watch for re-emergence.

List B Species Designated by the Board of County Commissioners for Required Management & Control

Bull thistle
Bull thistle
Cirsium vulgare

Canada thistle
Canada thistle
Cirsium arvense

Common teasel
Common teasel
Dipsacus fullonum

Dalmatian toadflax
Dalmatian toadflax
Linaria dalmatica & genistifolia

Diffuse knapweed
Diffuse knapweed
Centaurea diffusa

Houndstongue
Houndstongue
Cynoglossum officinale

Leafy spurge
Leafy spurge
Euphorbia esula

Musk thistle
Musk thistle
Carduus nutans

Russian knapweed
Russian knapweed
Acroptilon repens​

Salt cedar
Salt cedar
Tamarix chinensis, T. parviflora, and
T. ramosissima

Scotch thistle
Scotch thistle
Onopordum acanthium

Spotted knapweed
Spotted knapweed
Centaurea stoebe

Treated as a List A Species in Boulder County

Yellow toadflax
Yellow toadflax
Linaria vulgaris

Other List B Species

Absinth wormwood
Absinth wormwood
Artemisia absinthium

Black henbane
Black henbane
Hyoscyamus niger

Bouncingbet
Bouncingbet
Saponaria officinalis

Chinese clematis
Chinese clematis
Clematis orientalis

Common tansy

Common tansy
Tanacetum vulgare

Cutleaf teasel
Cutleaf teasel
Dipsacus laciniatus

Dame's rocket
Dame’s rocket
Hesperis matronalis

Eurasian watermilfoil
Eurasian watermilfoil
Myriophyllum spicatum

Hoary cress
Hoary cress
Cardaria draba

Hybrid knapweed
Hybrid knapweed
Centaurea x psammogena = C. stoebe x C. diffusa

Hybrid toadflax
Hybrid toadflax
Linaria vulgaris x L. dalmatica

Jointed goatgrass
Jointed goatgrass
Aegilops cylindrica

Mayweed chamomile
Mayweed chamomile
Anthemis cotula

Moth mullein
Moth mullein
Verbascum blattaria

Oxeye daisy
Oxeye daisy
Chrysanthemum leucanthemum

Perennial pepperweed
Perennial pepperweed
Lepidium latifolium

Plumeless thistle
Plumeless thistle
Carduus acanthoides

Russian-olive
Russian-olive
Elaeagnus angustifolia

Scentless chamomile
Scentless chamomile
Matricaria perforata

Sulfur cinquefoil
Sulfur cinquefoil
Potentilla recta

Wild caraway
Wild caraway
Carum carvi

Yellow nutsedge
Yellow nutsedge
Cyperus esculentus

Management is recommended, but not required, for List C Species.

Bulbous bluegrass
Bulbous bluegrass
Poa bulbosa


Chicory
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
Halogeton glomeratus


Johnsongrass
Sorghum halepense


Perennial sowthistle
Sonchus arvensis


Poison hemlock
Conium maculatum


Puncturevine
Tribulus terrestris


Quackgrass
Elymus repens


Redstem filaree
Erodium cicutarium


Velvetleaf
Abutilon theophrasti


Wild-proso millet
Panicum miliaceum

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 in order to facilitate the collection of information to assist in determining which species should be designated as noxious weeds.

Baby's breath
Baby’s breath
Gypsophila paniculata

Baby's breath
Caucasian bluestem
Bothriochloa bladhii


Common bugloss
Anchusa officinalis


Common reed
Phragmites australis


Garlic mustard
Alliaria petiolata

Garden loosestrife
Garden loosestrife
Lysimachia vulgaris

Himalayan blackberry
Himalayan blackberry
Rubus armeniacus

Himalayan blackberry
Hoary alyssum
Berteroa incana


Meadow hawkweed
Hieracium caespitosum


Onionweed
Asphodelus fistulosus


Siberian elm
Ulmus pumila


Scotch broom
Cytisus scoparius


Swainsonpea
Sphaerophysa salsula


Syrian beancaper
Zygophyllum fabago


Tree of Heaven
Ailanthus altissima


Ventenata grass
Ventenata dubia


White bryony
Bryonia alba


Yellow bluestem
Bothriochloa ischaemum


Yellow flag iris
Iris pseudacorus

Photos are provided courtesy of the Colorado Department of Agriculture.

Contact Us

Community Planning & Permitting (formerly the Land Use Dept.)

Email: Ask a Planner Form
Main: 303-441-3930

Courthouse Annex Building

2045 13th St.
Boulder, CO 80302

Hours

8 a.m. to 3 p.m. Monday, Wednesday, Thursday
10 a.m. to 3 p.m. Tuesday
Map and Directions

Mailing Address

Community Planning & Permitting
PO Box 471
Boulder, CO 80306
Community Planning & Permitting website