Other Names: cheatgrass, downy chess, early chess, drooping brome, downy cheat, slender chess, downy bromegrass, military grass, broncograss, Mormon oats

USDA Code: BRTE, ANTE6

Legal Status: Colorado List C

Growth form: Annual or winter annual grass

Flower: Downy brome panicles (loose, irregularly compound flowering part of plant with flowers borne on individual stalks) change color from green to purple to brown as the plant matures and eventually dries out. Branches are slender, drooping, hairy, flexuous, with up to eight spikelets.

Seeds/Fruit: Spikelets including awns are 0.8-2 inches long, nodding, with 2-8 florets.

Leaves: Leaves are light-green and hairy. Sheaths are fused except near the node at the bottom of each sheath. The lower sheaths are conspicuously hairy, while the upper sheaths are sometimes smooth.

Roots: Finely divided fibrous root system that can reach a depth of about 12 inches.

Seedling: Downy brome seedlings can usually be distinguished by their hairy leaf blades and sheaths.

Similar Species

Exotics: Similar to Japanese brome (Bromus japonicus).

Natives: None known.

Ecological: Downy Brome can greatly alter the species composition of dry native rangeland vegetation by competitive exclusion of reproduction of native plant species and by facilitation of wildfires (Mosky et al. 1999). Invasion of downy brome is greatest in drier environments, particularly in sagebrush-steppe communities. The process in which a pristine Great Basin shrub-steppe ecosystem deteriorates into one that is dominated by downy brome takes several years and has several distinct cycles. First, some sort of disturbance, such as heavy grazing, allows downy brome and other annuals to invade and proliferate. The dry stands of downy brome in the summer increase the occurrence of frequent fires. Initially, this creates an environment dominated by annual grasses, matchweed (Gutierrezia sarothrae), and rabbitbrush (Chrysothamnus spp.). As fires become even more frequent, the area will be dominated by annual grasses alone, with the loss of surface soil, nutrients, and near permanent deterioration of the site. Species that are commonly displaced by downy brome include big sagebrush (Artemisia tridentata), antelope bitterbrush (Purshia tridentata), bluebunch wheatgrass (Agropyron spicatum = Pseudoroegneria spicata ), crested wheatgrass (Agropyron cristatum), western wheatgrass (Agropyron smithii = Pascopyrum smithii), Sandberg bluegrass (Poa sandbergii = Poa secunda), needle-and-thread grass (Stipa comata = Hesperostipa comata), and Thurber’s needlegrass (Stipa thurberiana)

Habitat and Distribution

General requirements: Downy brome is common in recently burned rangeland and wildlands, winter crops, waste areas, abandoned fields, eroded areas, and overgrazed grasslands (Upadhyaya et al. 1986). It can invade rangelands that have never been grazed by livestock (Svejcar and Tausch 1991).

Distribution: Common throughout Colorado from 4,000 to 9,000 feet. Widely distributed throughout North America. Although downy brome occurs in a variety of habitats, it is most prominent on the Columbia-Snake River Plateau, Wyoming Basin, and the northern edge of the Great Basin in disturbed sagebrush steppe communities (Rice and Mack 1991, West 1983).

Biology/Ecology

Life cycle: Vast numbers of downy brome seedlings usually germinate after the first fall rain in infested areas (West 1983). The leaves typically grow little in the fall, and plants are normally 1-2 inches in height when covered by snow in December. The young, fall-germinated seedlings often over-winter in a semi-dormant state and complete their lifecycle the following spring (Upadhyaya et al. 1986). However, downy brome roots can grow in soil temperatures approaching freezing (West 1983), and roots will continue to grow throughout the winter until soil temperatures drop below about 37 degrees F. Plants head in late April to early May followed by flowering within a week (Upadhyaya et al. 1986). The seeds reach the soft dough-stage in mid to late May, and mature in mid to late June (Upadhyaya et al. 1986).

During ripening downy flowers turn purple and then brown as they mature. Once the seeds have matured, downy brome plants dry and become flammable. There is a correlation between plant color and moisture status during the drying process (FEIS 1998). Downy brome passes from green (>100% moisture content), to a purple hue (30-100% moisture content), to a straw color (<30% moisture content) as it dries (FEIS 1998). The onset of purple coloring should be taken as a warning that hazardous fire conditions will develop within two weeks (FEIS 1998).

Downy brome greens up earlier in the spring than most other species. Depletion of soil moisture is a mechanism by which downy brome suppresses seedlings of desirable, perennial grasses (Melgoza et al. 1990). In addition, thick mulch in dense cheatgrass stands favors cheatgrass seedling germination and establishment while inhibiting that of perennial bunchgrasses (Svejar and Tausch 1991).

Mode of reproduction: Reproduces by seeds.

Seeds production: Downy brome can be a prolific seed producer and is capable of producing up to 400 lbs. of seeds acre (Upadhyaya et al. 1986). Seed production per culm, per plant, and per unit area is dependent on plant density and environmental factors (Upadhyaya et al. 1986). Average seed production per plant is generally lowest where plant density is highest (Rice and Mack 1991). If precipitation is adequate, the majority of downy brome seeds will germinate in the fall, or within a year of maturation (Upadhyaya et al. 1986). However, dry conditions can cause environmentally induced dormancy, which may last several years and break down at erratic intervals (Young and Evans 1985).

Seed bank: Low survival rates in the soil, but seeds may last in the seed bank for a few years.

Dispersal: Seeds are dispersed short distances by wind, and the long awns can attach to the fur or feathers of an animal, as well as clothing.

Downy brome is characterized by its early maturation, high seed production, and vigorous growth under favorable environmental conditions. Although, downy brome readily invades perennial forage crops and rangeland under poor management, it also invades communities in the absence of disturbance (Douglas et al. 1990). In undisturbed sites, downy brome will most commonly spread along soil cracks and work its way outward into the natural community (Rice and Mack 1991). Downy brome has a dual role as a serious weed and important early season forage for cattle and sheep (Upadhyaya et al. 1986). Downy brome provides the bulk of early spring forage for all classes of stock on grazing lands in the Intermountain and Pacific Northwest regions (Upadhyaya et al. 1986). Lasting control of downy brome will require a combination of chemical control, physical control, vegetative suppression, and proper livestock management where land is grazed. This "cumulative stress" method will keep the plants constantly under stress, reducing their ability to flourish and spread. Also, a cumulative stress approach provides a level of redundancy in case one type of treatment is not implemented or proves to be ineffective (Carpenter and Murray 1998).

Carpenter, A.T. and T.A. Murray. 1998. Element Stewardship Abstract for Bromus tectorum. The Nature Conservancy, Wildland Weed Program. Internet: http://tncweeds.ucdavis.edu

Douglas, B.J., A.G. Thomas, and D.A. Derksen. 1990. Downy brome (Bromus tectorum) invasion into southwestern Saskatchewan. Canadian Journal of Plant Science 70:1143-1151.

FEIS - Fire Effects Information System [Online] (1996, September). Prescribed Fire and Fire Effects Research Work Unit, Rocky Mountain Research Station (producer), US Forest Service. Available: www.fs.fed.us/database/feis/ [1998,March 12]

Melgoza, G., R.S. Nowak and R.J. Tausch. 1990. Soilwater exploration after fire: competition between Bromus tectorum and two native species. Oceologia 83:7-13.

Mosely, J.C., S.C. Bunting, and M.E. Monoukian. 1999. Cheatgrass. In: R.L. Sheley and J.K. Petroff (eds.) Biology and management of noxious rangeland weeds. Oregon State University Press, Corvallis. pg. 175-188.

Mosely, J.C. 1996. Prescribed sheep grazing to suppress cheatgrass: A review. Sheep and Goat Research Journal 12:74-81.

Ponzetti, J.M. 1997. Assessment of medusahead and cheatgrass control techniques at Lawrence Memorial Grassland Preserve 1996 Annual Report. The Nature Conservancy of Oregon. January 14, 1997.

Rice, K.J., and R.N. Mack. 1991. Ecological genetics of Bromus tectorum: intraspecific variation in phenotypic plasticity. Oecologia 88:84-90.

Svejcar, T. and R. Tausch. 1991. Anako Island, Nevada: A relict area dominated by annual invader species. Rangelands 13: 233-236.

Upadhaya, M.K., R. Turkington, and D. McIlvride. 1986. The biology of Canadian weeds. 75. Bromus tectorum L. Canadian Journal of Plant Science 66:689-709.

West, N.E. 1983. Western intermountain sagebrush steppe. Temperate Deserts and Semi-Deserts. Elsevier Scientific Publishing Company, Amsterdam. pp. 351-373.

Whitson, T.D. and D.W. Koch. 1998. Control of downy brome (Bromus tectorum) with herbicides and perennial grass competition. Weed Technology 12:391-396.

Wiese, A.F., C.D. Salisbury, and B.W. Bean. 1995. Downy brome (Bromus tectorum), jointed goatgrass (Aegilops cylindrica) and horseweed (Conyza canadensis) control in fallow. Weed Technology 9:249-254.

Young, J.A. and R.A. Evans. 1985. Demography of Bromus tectorum in Artemisia communities. J. White (ed.), The Population Structure of Vegetation. Dr. W. Junk Publishers, Dordrecht, Netherlands.