Cheatgrass

Cheatgrass is a winter annual grass in the Poaceae family. Seeds may germinate in early spring or late fall. It produces slender, 4 to 30 inch long stems that may be erect or decumbent (lying over near the ground). These stems are covered in soft hairs which are especially prominent early in the season. Leaves are narrow (1 to 6 mm wide) and 2 to 6 inches long. Leaf blades are open and have a slight twist from bottom to top. Leaves may be glabrous or have short, stiff hairs. Sheaths are closed on lower leaves. Ligules are 2 mm long, membranous, and frayed at the margins. Auricles are not present. Cheatgrass flowers from mid-spring to early summer. Inflorescences are branched panicles that may be between 2 and 6 inches long. These panicles are composed of clusters of spikelets containing 5 to 8 flowers. Panicles usually droop to one side. Seeds are formed in awns that are around 2 cm long. Seeds are viable for up to 5 years. Cheatgrass has a shallow, fibrous root system.

Stems, leaves, and inflorescences of cheatgrass begin the season bright green but quickly turn red to purple as seeds mature in late spring. By early summer, cheatgrass plants will have completed their life cycle. Plants die back leaving dense stands of blonde or tawny-colored straw. Cheatgrass plants contain high amounts of silica which slows the decomposition of the dead plant material and creates dense patches of thatch or duff.

Cheatgrass is native to southwestern Asia. It has had several points of introduction to North America with the first introduction likely occurring through ship ballasts near St. Louis, Missouri in the 1800s. It creates dense infestations by completing most of its life cycle before many native species have started growing, allowing cheatgrass to produce up to 500 seeds per plant. These dense infestations further reduce competition from other species through alteration of fire regimes. The dense thatch layers left behind each growing season feed hotter and more frequent fires that native vegetation, like sagebrush, can withstand.

Cheatgrass is frequently found in sites disturbed by construction and development as well as those disturbed by wildlife including ground squirrels and bison. After establishing in disturbed sites, cheatgrass moves into arid rangeland sites including sagebrush habitat.

Prevention strategies and cultural control strategies should be utilized as much as possible.

There are not currently any biological control agents available for cheatgrass.

Hand pulling of small infestations of cheatgrass, prior to seed maturation, is highly effective. Shallow cultivation including tilling or hoeing is also effective if conducted immediately after germination and prior to flower production. Mowing is not recommended. Grazing is also not frequently effective, and care should be taken as ergot, a poisonous fungus, can be found on cheatgrass.

Large infestations can be controlled with herbicides. With the exception of glyphosate, herbicides should be applied preemergence to prevent germination. Glyphosate is only effective on cheatgrass prior to seed production. Application timing for preemergent herbicides varies based on moisture or rainfall requirements, but most can be applied in August. Read the label before using any herbicide and for application timing details. Contact TCWP if you have any questions about application rates or how to use an herbicide.

• Cheatgrass: Identification, biology and integrated management (2017) Menalled, F., Mangold, J., Orloff, N., and Davis, E. Montana State University Extension.
• Field Guide for Managing Cheatgrass in the Southwest (2014) United States Department of Agriculture Forest Service Southwest Region.
• Weed Report: Ripgut, red, and downy brom (cheatgrass) (2013) DiTomaso, J.M., Kyser, G.B., et al. Weed Control in Natural Areas in the Western United States. University of California Weed Research and Information Center.
• How to Get Rid of Cheatgrass (2022) Mann, J.J., Miller, W., and Buhl, K. Oregon State University Department of Horticulture.