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Introduction
This is an introduced, self-pollinating (sometimes cross-pollinating) (Thill et al. 1984) winter annual species native to Europe and southwestern Asia: it is now present throughout Europe, western and central Asia, Japan, South Africa, Canada and the United States, and Australia and New Zealand [there are recent reports from South America and India] (Global Invasive Species Database 2005). It was brought to North America circa 1860 as livestock forage (Global Invasive Species Database 2005), with the first collection made from Pennsylvania in 1861 (Stewart and Hull 1949). By 1928 it invaded much of the perennial grasslands of Washington, Idaho, Oregon, Utah, Nevada and British Columbia. It presently carpets areas of occurrence as a dominant species (Humphrey and Schupp 2001), including throughout the Okanagan. It is a fire-prone, ecosystem altering species, and can out-compete native species particularly following fire (Global Invasive Species Database 2005). Increased fire risk is associated with increased cover of cheatgrass (Link et al. 2006). Recruitment occurs in late summer and autumn, but may continue into the next year (Mack and Pyke 1983). This is a seed banking species; seed banks are reduced by fire, but recover quickly (Humphrey and Schupp 2001). Cheatgrass is bright green when young, turning a straw colour when old and dried--its most flammable period (Globa Invasive Species Database 2005). The earliest BC collection for this species in the UBC Herbarium was made by Eli Wilson in 1912, from Summerland in the Okanagan. It was collected from Spence's Bridge by John Davidson in 1913.
Species Information
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expanded illustration for this species.
General: Annual grass from fibrous roots; stems more or less densely hairy, the hairs fine, soft, short to moderately long and straight, (10) 20-50 (70) cm tall.
Leaves: Sheaths soft-hairy; blades 2-3 (4) mm wide, flat, hairy, the hairs fine, soft, short to moderately long, straight; ear-shaped lobes lacking at the leaf-bases; ligules jagged, 1.2-3 mm long.
Flowers: Inflorescence a somewhat compact panicle, erect at first then mostly drooping to one side, (3) 6-15 cm long, the branches slender, the lower and longer ones often drooping, bearing usually (3) 4 or more spikelets; spikelets 3- to 6-flowered, slender, broadest above the midlength, smooth, up to 2 cm long; florets mostly small, closed, self-fertilizing; glumes smooth to long-hairy, the lower ones 1-nerved, 4-6 (9) mm long, the upper ones 3-nerved, 7-13 mm long; lemmas smooth to long-hairy, slightly keeled, 9-12 mm long, narrowly sharp- to long-pointed, often purplish when mature, awned, the awns straight to slightly bent, 10-17 mm long, bidentate, the teeth long pointed, 2-3 mm long; anthers 0.5-0.7 mm long, usually included.
Dry to mesic roadsides, disturbed sites, waste places, meadows, grasslands and shrublands in the lowland, steppe and montane zones; common in S BC, rare elsewhere; introduced from Eurasia and N Africa.
There are several grasses that cheatgrass or downy brome can be mistaken for, mostly species with drooping panicles and conspicuous awns. Care should be taken with species that grow in similar habitat conditions, like dry grasslands and meadows, roadsides and waste places in the lowland, steppe and montane zones.
From among the many brome species present in BC, the poverty brome (Bromus sterilis) has similarly lax inflorescences and panicle branches longer than the spikelets, which result in a drooping inflorescence. However, its spikelets are longer (more than 3 cm), as opposed to those of the cheatgrass, which are shorter than 3 cm. The two species can also be differentiated based on the branching. Poverty brome has simple branching and while cheatgrass always has compound branches. The Japanese brome (Bromus japonicus) is also an undesirable weed, and looks very similar to cheatgrass, but its awns are twisted and bent. Other dry habitat bromes with conspicuous awns are are the rip-gut brome (B. rigidus), the meadow brome (B. commutatus), the bald brome (B. racemosus), the rye brome (B. secalinus), and the corn brome (B. squarrosus). The first species has much longer awns (3.5-6 cm) than those of the cheatgrass (1-1.7 cm), whereas the other four species have generally shorter awns, or no awns, and their inflorescences are usually more slender, not so drooping as cheatgrass.
Oats, such as the common or cultivated oat and the wild oat (Avena sativa and A. fatua), might also be mistaken for cheatgrass from a distance because of their drooping inflorescences. Yet, these species can be easily differentiated from the brome species based on the fewer florets in the spikelet (three), as opposed to the bromes, which have several florets. The awns in oats are long, but strongly bent, not strait as in the cheatgrass.
North Africa grass or ventenata (Ventena dubia), also originating from Eurasia, is still rare in BC, but could be mistaken for cheatgrass. It has spreading or drooping inflorescence, but the spikelets have only three florets and the awns are very tiny, 1-3 mm long.
Note Author: Anna-Mária Csergo, February 2011.
Ecology
Ecological Framework for Bromus tectorum
The table below shows the species-specific information calculated from original data (BEC database) provided by the BC Ministry of Forests and Range. (Updated August, 2013)
Global Invasive Species Database. 2005. Bromus tectorum page. Invasive Species Specialist Group, International Union for the Conservation of Nature.
Humphrey, L. David and Eugene W. Schupp. 2001. Seed banks of Bromus tectorum-dominated communities in the great basin. Western North American Naturalist 61 (1): 85-92.
Link, S.O., Keeler, C.W., Hill, R.W. and Hagen, E. Bromus tectorum cover mapping and fire risk. International Journal of Wildland Fire 15 (1): 113-119.
Mack, Richard N. and David A. Pyke. 1983. The demography of Bromus tectorum: variation in time and space. Journal of Ecology 71: 69-93.
Stewart, George and A. C. Hull. Cheatgrass (Bromus tectorum L.)--An Ecologic Intruder in Southern Idaho. Ecological Society of America.
Thill, Donald C., K. George Beck, and Robert H. Callihan. 1984. The Biology of Downy Brome (Bromus tectorum). Weed Science 32: Supplement 1: 7-12.
