Douglas County

Conservation District

 Noxious Weeds offer little food value for wildlife and livestock.  They out compete and crowd out native and more desirable plants.  Some are toxic to animals and humans.  They reduce crop production and reduce land values.  They increase soil erosion and the loss of precious topsoil.   This site is to educate landowners about these weeds to first identify them then work on preventing them from spreading.  The following are some species that are currently on either the A, B, or C List of the Colorado Noxious Weed Act

 

Noxious Weeds List C Species

Common Burdock Arctium minus   (C)

Mullein along roadsides in the US is very common.  Everyone knows Mullein’s long, fuzzy, rabbit-ear leaves.  Many clumps of these leaves often surround old, dried, contorted mullein flower stalks. 

 

Mullein flowers are quite small, bright yellow, with only a few blooming at a time, dying, and then being overshadowed by a few new flowers blooming higher up the ever-elongating flower stalk.

 

Each stalk contains hundreds of seeds which disperse, germinate, and eventually spread.

 

 

 

Common Mullein Verbascum  thapsus  (C)

Helping People Help the Land ~ Colorado

Downy Brome Bromus tectorum  (C)

 List C Species (14  species-list at bottom of page)

 

 

 

 

The above is a small segment from the Colorado Noxious Weed Act.   To view the complete Colorado Noxious Weed Act, go to www.ag.state.co.us/CSD/weeds/statutes/weedrules.pdf                A few species below on List C.

 

 

Puncturevine Tribulus terrestris (C)

Field Bindweed Concolculus arvensis  (C)

Common burdock is a member of the Aster or Sunflower family.  It is an introduced biennial which reproduces by seeds. In the first year of growth the plant forms a rosette. The second year the plant is erect. The stem is stout, grooved, rough, has multiple branches, and grows to 2-6 feet tall. The leaves are alternate, dark green, smooth above, whitish green, and woolly-hairy beneath. The flowers are purple or white in numerous heads. The head is enclosed in a prickly bur, composed of numerous smooth or woolly bracts tipped with hooked spines.

Burdock grows along roadsides, ditch banks, and neglected areas. This plant is a very serious threat to sheep as the burs can significantly damage the quality of the wool. Burdock is very common in central and north central Colorado.

Field bindweed is a problem throughout Colorado. It is one of the most competitive perennial weeds. A two or three-year food supply is stored in the extensive underground root system. This makes it hard to kill by cultivation because roots will live as long as their food reserve lasts. Seeds can also stay viable in the soil for up to 40 years. It is widespread in cultivated areas, pastures, lawns, gardens, roadsides, and waste areas throughout Colorado from 4,000 to 8,000 feet.

Puncturevine is a member of the Caltrop family and is an introduced annual which reproduces by seeds. It is a prostrate, matforming plant with trailing stems, each 1 to 6 feet long and hairy. The leaves are opposite, pinnate, one to two inches long with four to eight pairs of leaflets. The yellow flowers are 1/4 to 1/2 inches wide with five petals. The fruit is a hard, spiny bud which at maturity breaks into five tack-like sections.

Puncturevine, also known as goathead, is most common in eastern Colorado up to 6,500 feet. It grows in pastures, cultivated fields, and waste places. The burs may injure livestock and are the bane of bicyclists.

Downy brome, a member of the Grass family, is an annual or winter annual introduced from Europe. It usually germinates in the fall, lies over winter, and produces seed early in the spring. It has smooth, slender, erect stems. The plant grows 6 inches to 2 feet high from a much-branched base. The sheathes and leaves are covered with fine, soft hair. The leaves are 1/8 to 1/4 inch wide and flat. The head is much-branched and somewhat drooping. Seeds are long and flat with an awn about as long as the seed. It matures and sets seed early spring, before most other grass species or crops.

Downy brome is a strong invader and creates a serious fire hazard when the mature plant dries. Mature plants turn purple or brown. It grows in fields, waste places, roadsides, and is widely distributed in Colorado from 4,000 to 9,000 feet. It is a serious small grain problem.