BoCo Alert System

Boulder County non-emergency offices will be closed on Monday, May 29 for Memorial Day.

Identification

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.

Mobile App

Download the noxious weed identification mobile app for iOS and Android.

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.

African rue
African rue

Peganum harmala

Camelthorn
Camelthorn

Alhagi pseudalhagi

Cypress spurge
Cypress spurge

Euphorbia cyparissias

Common crupina
Common crupina

Crupina vulgaris

Dyer's woad
Dyer’s woad

Isatis tinctoria

Giant salvinia
Giant salvinia

Salvinia molesta

Hydrilla
Hydrilla
Hydrilla verticillata

Meadow knapweed
Meadow knapweed
Centaurea pratensis

Mediterranean sage
Mediterranean sage
Salvia aethiopis

Camelthorn
Camelthorn

Alhagi pseudalhagi

Medusahead
Medusahead
Taeniatherum caput-medusae

Myrtle spurge
Myrtle spurge
Euphorbia myrsinites

Orange hawkweed
Orange hawkweed
Hieracium aurantiacum

Purple loosestrife
Purple loosestrife
Lythrum salicaria

Rush skeletonweed
Rush skeletonweed
Chondrilla juncea

Squarrose knapweed
Squarrose knapweed
Centaurea virgata

Tansy ragwort
Tansy ragwort
Senecio jacobaea

Yellow starthistle
Yellow starthistle
Centaurea solstitialis

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.

Absinth wormwood
Absinth wormwood

Artemisia absinthium

Black henbane
Black henbane

Hyoscyamus niger

Bouncingbet
Bouncingbet

Saponaria officinalis

Bull thistle
Bull thistle

Cirsium vulgare

Canada thistle
Canada thistle

Cirsium arvense

Chinese clematis
Chinese clematis

Clematis orientalis

Common tansy
Common tansy

Tanacetum vulgare

Common teasel
Common teasel

Dipsacus fullonum

Corn chamomile
Corn chamomile

Anthemis arvensis

Cutleaf teasel
Cutleaf teasel

Dipsacus laciniatus

Dalmatian toadflax
Dalmatian toadflax

Linaria dalmatica & genistifolia

Dame's rocket
Dame’s rocket

Hesperis matronalis

Diffuse knapweed
Diffuse knapweed

Centaurea diffusa

Eurasian watermilfoil
Eurasian watermilfoil

Myriophyllum spicatum

Hoary cress
Hoary cress

Cardaria draba

Houndstongue
Houndstongue

Cynoglossum officinale

Leafy spurge
Leafy spurge
Euphorbia esula

Mayweed chamomile
Mayweed chamomile
Anthemis cotula

Moth mullein
Moth mullein
Verbascum blattaria

Musk thistle
Musk thistle
Carduus nutans

Oxeye daisy
Oxeye daisy
Chrysanthemum leucanthemum

Perennial pepperweed
Perennial pepperweed
Lepidium latifolium

Plumeless thistle
Plumeless thistle
Carduus acanthoides

Russian knapweed
Russian knapweed
Acroptilon repens​

Russian-olive
Russian-olive
Elaeagnus angustifolia

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

Scentless chamomile
Scentless chamomile
Matricaria perforata

Scotch thistle
Scotch thistle
Onopordum acanthium

Spotted knapweed
Spotted knapweed
Centaurea stoebe

Sulfur cinquefoil
Sulfur cinquefoil
Potentilla recta

Wild caraway
Wild caraway
Carum carvi

Yellow nutsedge
Yellow nutsedge
Cyperus esculentus

Yellow toadflax
Yellow toadflax
Linaria vulgaris

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.

Asian mustard
Asian mustard
Brassica tournefortii

Baby's breath
Baby’s breath
Gypsophila paniculata

Brazilian elodea
Brazilian elodea
Egeria densa

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 alyssum
Hoary alyssum
Berteroa incana

Japanese blood grass
Japanese blood grass/
Cogongrass

Imperata cylindrical

Meadow hawkweed
Meadow hawkweed
Hieracium caespitosum

Onionweed
Onionweed
Asphodelus fistulosus

Purple pampasgrass
Purple pampasgrass
Cortideria jubata

Scotch broom
Scotch broom
Cytisus scoparius

Sericea lespedeza
Sericea lespedeza
Lespedeza cuneata

Swainsonpea
Swainsonpea
Sphaerophysa salsula

Syrian beancaper
Syrian beancaper
Zygophyllum fabago

Water hyacinth
Water hyacinth
Eichhornia crassipes

Water lettuce
Water lettuce
Pistia stratiotes

White bryony
White bryony
Bryonia alba

Woolly distaff thistle
Woolly distaff thistle
Carthamus lanatus

Yellow flag iris
Yellow flag iris
Iris pseudacorus

Yellow floatingheart
Yellow floatingheart
Nymphoides peltata

Photos are provided courtesy of the Colorado Department of Agriculture.

Contact Us

Land Use

Email: Ask a Planner Form
Main: 303-441-3930
Fax: 303-441-4856

Courthouse Annex Building

2045 13th Street
Boulder, CO 80302
Hours:
8 a.m. - 4:30 p.m. M, W, Th, F
10 a.m. - 4:30 p.m. Tuesday
Plan review services for building permits are not available on Tuesdays. Building permits can be applied for and issued until 4 p.m.
Map & Directions

Mailing Address

PO Box 471
Boulder, CO 80306
www.BoulderCounty.org/lu