Plants perennial. Culms 45-120(180) cm tall, to 3 mm thick. Sheaths usually sparsely retrorsely pilose throughout, ranging from densely pilose to glabrous, except at the throat, throats always pilose; auricles sometimes present on the lower leaves; ligules 1-3.5 mm, sparsely hairy, acute to obtuse, erose or lacerate; blades 8-25 cm long, 1-12 mm wide, flat or involute, glabrous or sparsely pilose to pubescent on 1 or both surfaces. Panicles 5-20(30) cm, erect; lower branches shorter than 10 cm, 1-4 per node, erect or ascending. Spikelets with 4-9 florets. Glumes sometimes pubescent; lower glumes 7-11 mm, 3-7(9)-veined; upper glumes 9-13 mm, 5-9(11)-veined; lemmas 10-14(17) mm, coriaceous, strongly keeled at least distally, pubescent on the backs and margins, on the margins only, or glabrous, 7-9-veined; awns 4-7 mm; anthers 1-6 mm. 2n = 42.

Plants perennial; loosely cespitose. Culms 60-120 cm tall, to 3 mm thick, erect, glabrous or puberulent. Sheaths usually smooth or scabrous, sometimes hairy except at the throat; auricles absent; ligules (1)2-2.5 mm, glabrous, obtuse, erose; blades 10-31 cm long, 2-9 mm wide, flat, sometimes scabrous, usually glabrous, rarely puberulent to pubescent near the collar. Panicles 10-20 cm, open to somewhat contracted; lower branches shorter than 10 cm, (1)2-3 per node, erect, ascending or spreading, with 1-2 spikelets variously distributed. Spikelets 20-35 mm, shorter than at least some pedicels and branches, elliptic to lanceolate, strongly laterally compressed, not crowded or overlapping, with 6-11 florets. Glumes smooth or scabrous; lower glumes (5.5)7-10(11.5) mm, 3-veined; upper glumes (7.5)9-11(12.5) mm, 5-7-veined, shorter than the lowest lemma; lemmas 12-15 mm, lanceolate, laterally compressed, strongly keeled at least distally, glabrous, sometimes scabrous, 7-9-veined, veins usually not raised or riblike, apices entire or with acute teeth, teeth shorter than 1 mm; awns 4-7 mm; anthers 1-5 mm. 2n = 56.

Bromus carinatus var. marginatus is primarily an inland species and grows on open slopes, grass balds, shrublands, meadows, and open forests, in montane and subalpine zones. It grows from British Columbia to Saskatchewan, south throughout the western United States, and also extends into northern Mexico. Its elevational range is 350-2200 m in the northern part of its distribution, and 1500-3300 m in the south.

Bromus carinatus var. marginatus is variable, and intergrades with B. carinatus var. carinatus-to the west, B. aleutensis-to the north, and B. polyanthus-to the southeast. As treated here, B. carinatus var. marginatus includes B. luzonensis J. Presl, which has been recognized mainly on the basis of its canescent sheaths and blades; this trait seems highly variable and may be environmentally determined. Although the name Bromus carinatus var. marginatus was attributed to Hitchcock by Scoggan, there is no evidence that either A.S. or C.L. Hitchcock actually made the combination.

Bromus polyanthus grows on open slopes and in meadows. It is found primarily in the central Rocky Mountains, but the limits of its range include British Columbia in the north, California in the west, and Arizona, New Mexico, and western Texas in the south. It is sometimes treated as var. polyanthus-with an erect, contracted panicle and awns 4-6 mm long; and as var. paniculatus-with an open, nodding panicle and awns up to 8 mm long. Because the variation in both characters is continuous, the varieties are not recognized here.

FNA 2007, Field Guide to Forest & Mtn. Plants of N AZ 2009, Utah Flora 1983; Ann. Checklist GCNP 1987

Common Name: mountain brome Duration: Perennial Nativity: Native Lifeform: Graminoid General: Short-lived perennial bunchgrass usually about 1 m tall,with a large, shallow, non-rhizomatous root system; stems erect, 45-150 cm, 3 mm thick, glabrous or minutely hairy. Vegetative: Sheaths often sparsely retrorsely pilose throughout; throats always pilose; auricles sometimes present on the lower leaves; ligules 1-4 mm long, sparsely hairy, irregularly toothed; blades 8-25 cm long, 1-12 mm wide, glabrous to pubescent. Inflorescence: Panicles 5-20 cm long; branches erect to ascending, less than 10 cm long, 1-4 per node; spikelets strongly compressed and keeled, 2-4 cm long, with 4-9 florets; glumes unequal, strongly keeled, lower glumes 7-11 mm, 3-7 veined, upper glumes 9-13 mm, 5-9 veined; lemmas strongly keeled, 10-14 mm long, 7-9 veined, pubescent on the back and margins, on the margins only, or glabrous; awns 4-7 mm long Ecology: Found in moister areas in shrublands, montane meadows, and open forests; elevation range in the southwest is 5,000-11,000 ft (1500-3353 m); flowers May-Sept. Distribution: British Columbia to Saskatchewan, south throughout the western United States, into northern Mexico. Notes: Considered a variety of B. carinatus in some treatments, including FNA; distinguished from B. carinatus var. carinatus by its shorter awns, higher elevation mountainous habitat, and perennial growth form (B. carinatus is considered annual to biennial). Also similar to B. arizonicus, but that species is always annual and occurs at lower elevations. According to FNA, B. marginatus is morphologically variable, and intergrades with B. carinatus var. carinatus to the west, B. aleutensis to the north, and B. polyanthus to the southeast. Important forage for deer, elk, and livestock, and its seeds are eaten by rodents and birds. Ethnobotany: Seeds were eaten; also, bunches of plants were tied together and used for hair brushes and brooms. Etymology: Bromus is from Greek bromo, for stinking, while marginata means margined with another color. Synonyms: Many, see Tropicos Editor: LKearsley 2012, AHazelton 2015