Weed of the Month

Leafy spurge

April 2020

Leafy Spurge Euphorbia escula

Leafy spurge is a perennial member of the spurge family.  This List B noxious weed reproduces by seed and spreading roots.  Seeds are expelled up to 15 feet from ripened seed pods and have a sticky gel-like substance on their surface that allows seeds to stick onto wildlife, pets, humans, and equipment.  Roots grow horizontally to 15 feet and vertically to 30 feet.  Plants can grow from root fragments as small as 1/8-1/4 inch long.  Roots have growth buds along their length that give rise to new plants.

Leafy spurge flowers from May through July.  The flower parts are inconspicuous and are found in the middle of modified bracts that are bright yellowish green.  These form clusters at the ends of stems.

Leaves are narrow, about 1-4 inches long, with smooth surfaces and edges.

Plants grow to about 3 feet tall.  Stems are thin.  Plants have a milky latex sap that can be toxic.  It can cause blistering on the lips of livestock.  Plants may appear reddish in the fall.

In some areas of Colorado Leafy spurge populations have declined significantly, in part due to biological control beetles. Visit CDA’s Insectary website for more info.

Leafy spurge is a problem in rangeland, pastures, parklands and riparian corridors.

Control includes good land management, biological control, and chemical.  Mowing or grazing with goats combined with other methods has shown results in some areas.

What You Can Do

  • Choose weed-free hay when feeding hay to livestock
  • Survey your property in early spring to identify patches of leafy spurge so you can control it before it seeds
  • Do not walk or drive through patches of leafy spurge

Resources

Team Leafy Spurge

USFS FEIS

CSU Extension Fact Sheet

CDA Factsheet  

hoary cress flower

March 2020

Hoary Cress Cardaria draba

Other Names: Whitetop, Heart-podded whitetop

Hoary cress is a List B perennial. This member of the mustard family reproduces by seed and rhizomes and can quickly form a monoculture.

Plants can be up to about 18 to 24 inches tall but are generally smaller. The leaves are dark green. Lower leaves have a petiole but leaves higher on the plant clasp the stem. Dense clusters of four-petaled white flowers grow at the ends of upright branches. Seedpods are slightly inflated and heart-shaped. Each plant produces up to 4800 seeds per year.

Large patches can be seen along roadsides and in parks in early spring. Hoary cress is also an agricultural pest in rangeland, pastures and in crops such as wheat.

Hoary cress has been known in Colorado since 1898. There are also two other weedy whitetops known in the state. Lens-podded whitetop (Cardaria chalapensis) and Hairy whitetop (Cardaria pubescens).

What You Can Do

Talk to your local park manager and see if they would like help locating patches of noxious weeds.

If you have Hoary cress on your property, treat it before it blooms.

Tell your neighbors. We will all benefit when more people become aware of the problem and take action.

Prevention

Clean your gear and equipment when moving between different sites. Whether you are a hiker, biker or work outdoors, weeds can easily be moved unintentionally by clinging to your clothing and equipment. Learn more at PlayCleanGo

Resources

Field Guide for Managing Whitetop in the Southwest

Weed Control in Natural Areas in the Western United States

CWMA Factsheet

CDA Factsheet

Myrtle spurge

February 2020

Myrtle Spurge

Myrtle spurge is a List A noxious weed commonly found in the urban and foothill areas of Colorado.  Initially sold as a xeriscape plant, this perennial of the spurge family, has escaped and naturalized in many areas including some remote and rugged areas.

Myrtle spurge shows up in early spring at lower elevations and begins to flower in March-April.

Grey-green leaves are fleshy, egg-shaped, and attach directly to the stem at their base.  Stems are stout and trail along the ground.  Leaves and stems contain a sticky, caustic sap that can cause severe rashes and blistering.

The inconspicuous flowers are surrounded by chartreuse bracts and develop at the ends of the stems.  When the seeds ripen, they are expelled from their capsule and are covered in a sticky gel that adheres the seeds to surfaces and passing animals.

Landowners are encouraged to start looking for this plant in mid-February.  It can be pulled as long as you remove the top few inches of the taproot.  Herbicides also work well.  The Colorado Department of Agriculture’s website has factsheets detailing control methods. 

More info:

USDA 

January 2020

Cheatgrass

Bromus tectorum

Cheatgrass is a winter annual grass that emerges in the fall and/or early spring. It has shallow fibrous roots and reproduces solely by seed. Seedlings are dark green and may be seen growing through previous years’ thatch. Mature plants can reach 20+ inches high but most plants are about 12 inches tall. Older plants are straw to red colored.

It can be found on all continents except Antarctica. It was introduced to North America in the mid-1800’s from Eurasia and was first noted in Colorado in 1892.

Cheatgrass matures earlier than native perennial grasses and its shallow roots utilize soil moisture and nutrients before deeper rooted plants can access them.

Cheatgrass burns hotter, quicker and more frequently than our native grasslands. The change in regime makes it harder for native grasslands to recover, making them even more susceptible to cheatgrass invasion.

Removal, grazing, or chemical treatment prior to any seed development are recommended controls. See the Cheatgrass Management Handbook: Managing an invasive annual grass in the Rocky Mountain Region for more information.


Fact Sheet