Plants perennial; cespitose, not rhizomatous. Culms (50)80-150 cm, stout, erect, not conspicuously branched; internodes smooth for most of their length, smooth or scabridulous below the nodes. Sheaths shorter or longer than the internodes, glabrous or puberulent, basal sheaths laterally compressed, usually keeled; ligules 10-25 mm, membranous throughout, acuminate, lacerate; blades 20-50 cm long, 2-6 mm wide, flat or folded, scabrous abaxially, smooth or scabridulous adaxially. Panicles 20-45 cm long, 3-15 cm wide, loosely contracted to open, light purplish to light brownish; primary branches 1-17 cm, lax, loosely appressed or diverging up to 70° from the rachises, naked basally; pedicels 0.5-3 mm, smooth or scabridulous. Spikelets 2.2-3.2 mm. Glumes subequal, 2.2-3.2 mm, exceeding the florets, scabridulous to scabrous, faintly 1-veined, acute to obtuse, usually unawned, occasionally awned, awns to 0.2 mm; lemmas 2-3 mm, oblong-elliptic, shortly pubescent on the lower 1/2-3/4, apices acute, usually awned, sometimes unawned, awns to 15 mm, flexuous, purplish; paleas 1.8-2.9 mm, oblong-elliptic, acute; anthers 1.2-1.6 mm, yellowish to purplish. Caryopses 1.3-1.6 mm, fusiform, reddish-brown. 2n = 24, 26, 28, 40, 42, 46, 60, 64.
Muhlenbergia emersleyi grows on rocky slopes, gravelly washes, canyons, cliffs, and arroyos, often in soils derived from limestone, at elevations of 1200-2500 m, and is also grown as an ornamental. Its range extends from the southwestern United States through Mexico to Panama.
Muhlenbergia emersleyi differs from the closely related M. longiligula in its compressed-keeled sheaths, pubescent florets, and membranous ligules.
FNA 2003, Gould 1980
Common Name: bullgrass Duration: Perennial Nativity: Native Lifeform: Graminoid General: Showy perennial bunchgrass with stout, erect, mostly unbranched stems 80-150 cm tall; internodes generally smooth. Vegetative: Leaves mostly basal; blades firm, long, slender, usually folded, 2-6 mm wide, 20-50 cm long, rough-textured on the lower surface and margins, midrib visible on underside of blade; ligule 10-25 mm long, thin and translucent, thin and often rayed/broken at Inflorescence: Large dense panicle, loosely contracted and never widely spreading, 10-40 cm long, light purple to light brown, many flowered, bare of spikelets near the base; primary branches 1-17 cm, lax to loosely appressed; glumes subequal 2-3 mm, membranous, awnless to short-awned, the awns to 0.2 mm; lemma purplish, 2-3 mm long, usually pubescent below, oblong elliptic, with awn 1-2 cm long, from between minutely notched apex. Ecology: Rocky slopes, ledges, forest openings, in dry soil; 3,500-6,500 ft (1065-1980m); flowers June-November. Distribution: AZ, s NM, sw TX; south to n MEX. Notes: Muhlenbergia is a large and diverse genus primarily distinguished by having single-flowered spikelets with unequal glumes. M. emerslyi is common and quite visible on slopes in the desert grasslands, with its basal bunch of long leaf blades, and large dense purple panicle topping an erect culm up to 1.5 m tall. The stems are flattened, the leaf bases folded, and the spikelets are awned. Distinguished from the similar M. longiligula by the flattened stem base, shorter ligule, and awns up to 2 cm long. Ethnobotany: Unknown Etymology: Muhlenbergia is named for Gotthilf Heinrich Ernst Muhlenberg (1753-1815) a clergyman and botanist from Pennsylvania; emersleyi is named for John D. Emersley an American botanist who collected in the Southwest in the 1880s-1890s. Synonyms: None Editor: SBuckley 2010, FSCoburn 2014, AHazelton 2015