Leon E. Pavlick and Laurel K. Anderton

Plants annual. Culms 5–90 cm, erect, slender, puberulent below the panicle. Sheaths usually densely and softly retrorsely pubescent to pilose, upper sheaths sometimes glabrous; auricles absent; ligules 2–3 mm, glabrous, obtuse, lacerate; blades to 16 cm long, 1–6 mm wide, both surfaces softly hairy. Panicles 5–20 cm long, 3–8 cm wide, open, lax, drooping distally, usually 1-sided; branches 1–4 cm, drooping, usually 1-sided and longer than the spikelets, usually at least 1 branch with 4–8 spikelets. Spikelets 10–20 mm, usually shorter than the panicle branches, sides parallel or diverging distally, moderately laterally compressed, often purplish-tinged, not densely crowded, with 4–8 florets. Glumes villous, pubescent, or glabrous, margins hyaline; lower glumes 4–9 mm, 1-veined; upper glumes 7–13 mm, 3–5-veined; lemmas 9–12 mm, lanceolate, glabrous or pubescent to pilose, 5–7-veined, rounded over the midvein, margins hyaline, often with some hairs longer than those on the back, apices acuminate, hyaline, bifid, teeth 0.8–2(3) mm; awns 10–18 mm, straight, arising 1.5 mm or more below the lemma apices; anthers 0.5–1 mm. 2n = 14.

Bromus tectorum is a European species that is well established in cool temperate regions throughout the world. It grows in disturbed sites, such as overgrazed rangelands, fields, sand dunes, road verges, and waste places. It is highly competitive but welcomed as early spring forage in areas where native grasses mature later. 

In North America, Bromus tectorum has become dominant in areas where the natural vegetation is sagebrush steppe and has changed the fire regime, the dense, fine fuel provided by Bromus tectorum permanently shortening the fire-return interval, further hindering reestablishment of native species. It now dominates large areas of the sagebrush ecosystem of the western Flora region. Schachnet et al. 2008 discuss the population genetics of this species in the midcontinental United States and cite earlier papers on a similar topic for other parts of the country.

Specimens with glabrous spikelets have been called Bromus tectorum forma nudus (Klett & Richt.) H. St. John. They occur throughout the range of the species, and are not known to have any other distinguishing characteristics. For this reason, they are not given formal recognition in this treatment.