Cheatgrass (Bromus tectorum)

Synonyms: Anisantha tectorum, Zerna tectorum, Bromus tectorum var. glabratus

Common Names: Downy brome, downy chess, bronco grass, drooping brome

Description:

Cheatgrass (Bromus tectorum) is an annual grass from Europe, North Africa, and southwestern Asia that reached North America in the 1800s as a contaminant in crop seed and ship ballast [1][2][3]. It now grows across most of the United States and is the dominant plant on more than 100 million acres of the western Great Basin [2][3]. MISIN tracks it because it produces huge numbers of seeds, dries into a continuous fuel, and feeds a fire cycle that wipes out native shrubs and grasses [2][4].

Habit:

Cheatgrass is a soft, fine-textured annual grass that usually grows 6 inches to 2 feet tall, though stressed plants can be tiny and crowded ones can reach 30 inches [2]. The leaves and leaf sheaths are covered in soft, downy hairs, which gives the plant its other common name, downy brome [2]. The flower head is a loose, drooping cluster (panicle) 2 to 8 inches long, with slender, nodding spikelets that each carry long, straight bristles called awns [2]. As the plant matures it often turns purplish, then dries to a pale tan or golden color [2].

It is easiest to spot in late spring and early summer. Cheatgrass greens up before most other plants, then flowers, sets seed, and dries out by early summer ? much earlier than native grasses ? leaving conspicuous reddish-purple to golden patches while everything around it is still green [2][3]. The dried, awned seeds cling to socks, shoelaces, and pet fur, which is often how people first notice it [2].

At-a-glance cues:

1. Soft, downy hairs cover the leaves and leaf sheaths [2]
2. Drooping, nodding flower head with long slender awns (bristles) on each spikelet [2]
3. Turns reddish-purple, then dries to pale tan, much earlier than nearby plants ? by early summer [2][3]
4. Sharp, dried seeds catch on socks, shoelaces, and pet fur [2]

Leaves:

1. Arrangement: blades spread along the stem, with sheaths wrapping the lower stem [2]
2. Shape: flat, narrow blades [2]
3. Surface: covered in soft, downy hairs, on both the blades and the sheaths [2]
4. Color: green when young, often turning purplish then drying to pale tan [2]

Stems:

1. Habit: herbaceous (non-woody) annual; a single plant may have one stem or many, from 2 to 30 inches (5 to 75 cm) tall depending on conditions [2]
2. Roots: fine, fibrous roots that can reach deep into the soil and use up moisture before native plants wake from dormancy [2]
3. Color: green, aging to purplish and then tan [2]

Flowers:

1. Color: green to purplish, drying to pale tan [2]
2. Shape: slender, drooping spikelets, each floret tipped with a long, straight awn (bristle) ? no showy petals, as is typical of grasses [2]
3. Arrangement: a loose, open, nodding flower head (panicle) 2 to 8 inches long [2]
4. Bloom time: spring to early summer, then the plant dries and dies [2][3]

Fruit and seeds:

1. Fruit type: a narrow dry grain held in an awned spikelet (the grass seed) [2]
2. Output: enormous ? a healthy plant can make from about 25 to several thousand seeds, and dense stands seed at very high rates per acre [2]
3. Seed bank: seeds stay alive in the soil for about 2 to 3 years, providing a reserve that refills after disturbance [2]
4. Dispersal: the sharp, awned seeds catch on fur, clothing, and shoes, and ride along on vehicles, equipment, and in hay [2]

Habitat:

Cheatgrass is native to Europe, North Africa, and southwestern Asia, eastward to Mongolia and China [1]. It was introduced to North America in the 1800s and now occurs across most of the United States and Canada [2][3].

It grows on a wide range of sites, almost always following disturbance ? rangelands, pastures, fields, roadsides, eroded ground, and waste areas [2]. It does best on deep, loamy, or coarse soils and in places that get about 12 to 22 inches of rain a year, with most of it in winter and spring [2]. In the western United States it dominates sagebrush steppe and bunchgrass country, and it is most aggressive in the Intermountain West [2].

Reproduction:

Cheatgrass spreads entirely by seed, and it makes a staggering amount [2]. The sharp, awned seeds hitch rides on clothing, shoes, and pet or livestock fur, and travel on vehicles, mowers, and in hay ? which is how it jumps to new ground [2]. Seeds left in the soil stay alive for about 2 to 3 years, so a patch can come back even after the visible plants are gone [2].

It is a winter annual: seeds sprout in fall when moisture returns, the seedlings live through winter, and the plants flower and set seed in spring or early summer before drying out [2]. Because it grows so early, its roots use up soil moisture before native plants break dormancy, giving it a head start [2]. For control timing, the key is to remove plants in spring before the seeds ripen ? once the seed heads dry, pulling them only scatters seed [2].

Impact and Damage:

For homeowners and landowners, cheatgrass is both a nuisance and a hazard. Its sharp, barbed seeds work into socks and shoelaces and into the mouths, ears, and paws of dogs and livestock, where they can cause painful sores [2]. Stands dry out early into a continuous mat of fine, golden tinder, raising the wildfire risk around homes and pastures [3]. It also lowers pasture quality, because it is only useful forage for a short window in spring [2].

For natural area stewards, cheatgrass is one of the most damaging invasive plants in the West because it changes how fire works. The dried plants form a continuous, highly flammable fuel that carries fire farther and more often [2][4]. A study across the arid western United States found that land dominated by cheatgrass burned far more frequently than other vegetation, and that cheatgrass was tied to many of the region's largest fires [4]. Native shrubs like sagebrush and native bunchgrasses cannot survive these frequent fires, while cheatgrass comes back fast and even thicker afterward ? one site went from about 10 plants per square meter a year after a fire to 10,000 plants per square meter three years later [2]. Each fire pushes the land further toward a cheatgrass monoculture, lowering plant diversity and degrading wildlife habitat, often permanently [2][4].

Similar species:

Several brome grasses are mistaken for cheatgrass. The surest checks are its soft, downy hairs on the leaves and sheaths and its drooping flower head with long, slender awns [2].

Japanese brome (Bromus japonicus) is the closest match ? another weedy annual brome of the same size and habitats. Its flower head is more stiffly spreading and its awns tend to twist or bend outward, while cheatgrass has a softer, one-sided, nodding head [2].

Ripgut brome (Bromus diandrus) is another nonnative annual brome with sharp, awned seeds. It is a coarser, taller plant with much larger spikelets and longer, stiffer awns than the fine-textured, smaller-seeded cheatgrass [2].

Smooth brome (Bromus inermis) is a common nonnative pasture grass sometimes confused with it. It is a tall perennial that spreads by underground stems and forms sod, and its seed heads have little or no awns, unlike the soft, long-awned, annual cheatgrass [2].

Monitoring and rapid response:

Signs to watch for:

1. Soft, downy-haired annual grass that greens up very early in spring [2]
2. Drooping, nodding flower heads with long slender awns, turning reddish-purple then golden tan by early summer [2][3]
3. Patches that dry out and die well before surrounding plants, leaving fine golden tinder, with sharp seeds that stick to clothing and fur [2][3]

What you can do:

1. Hand-pull or hoe young plants in spring, while they are still green and before the seed heads ripen ? cheatgrass is shallow-rooted and pulls easily [2]
2. Bag and remove any plants that already have seed heads, since the dried seeds scatter and cling readily [2]
3. Mow or cut just as the flower heads form but before seeds harden, to cut down seed production; repeat, because seedlings keep emerging [2]
4. Reseed or plant cleared ground with vigorous native or desirable plants, since bare, disturbed soil is exactly what cheatgrass colonizes [2]
5. For natural areas, volunteer crews should map and treat small outlying patches first, work to deplete the 2-to-3-year seed bank with repeated spring visits, and clean seeds off boots, gear, and vehicles to avoid spreading it [2]

When to call a professional:

1. Large rangeland, pasture, or natural-area infestations, especially where the dried grass has raised the wildfire risk [3][4]
2. Sites where repeated removal has not drawn down the seed bank and a coordinated, multi-year plan is needed [2]
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Plants of the World Online (POWO), Royal Botanic Gardens, Kew. Bromus tectorum L. powo.science.kew.org
2. Zouhar K (2003). Bromus tectorum. In: Fire Effects Information System (FEIS). U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. research.fs.usda.gov
3. USDA National Invasive Species Information Center. "Downy Brome (Bromus tectorum)." invasivespeciesinfo.gov
4. Balch JK, Bradley BA, D'Antonio CM, Gomez-Dans J (2013). "Introduced annual grass increases regional fire activity across the arid western USA (1980?2009)." Global Change Biology 19(1):173?183. semanticscholar.org

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