Plants perennial; cespitose, with knotty bases, not rhizomatous. Culms 20-60 cm tall, 1-2 mm thick, erect, not rooting at the lower nodes; internodes mostly glabrous or sparsely hispidulous, always hispidulous below the nodes. Sheaths shorter than the internodes, laterally compressed, keeled, smooth or scabridulous, not becoming spirally coiled when old; ligules 0.2-0.8 mm, membranous, truncate; blades 2-22 cm long, 0.5-2.7(3.5) mm wide, flat to folded, smooth or scabridulous abaxially, strigose adaxially. Panicles 4-14 cm long, 0.1-0.8 cm wide, spikelike, not dense; primary branches 0.4-3 cm, appressed; pedicels 0.1-1.2(4) mm. Spikelets 2.5-3.6 mm, dark green or plumbeous, occasionally with 2 florets. Glumes subequal, 1.2-3 mm, about 3/4 as long as the spikelets, 1-veined, gradually acute to acuminate, occasionally mucronate, mucros to 0.3 mm; lemmas 2.5-3.6 mm, lanceolate, sometimes mottled with greenish-black areas, with short, appressed hairs on the basal 1/2-3/4 of the midveins and margins, apices acuminate, sometimes mucronate, mucros to 0.6 mm; paleas 2.4-3.6 mm, lanceolate, glabrous, acuminate; anthers 1.2-1.8 mm, greenish. Caryopses 1.6-2.3 mm, fusiform, brownish. 2n = 20.
Muhlenbergia cuspidata grows in dry, gravelly prairies, on gentle rocky slopes, rocky limestone outcrops, and in sandy drainages, at elevations of 300-1400 m, primarily in the central portion of the Flora region. It flowers from June to October.
Muhlenbergia cuspidata is often confused with M. richardsonis, but that species has rhizomes and longer ligules. Morden and Hatch (1984) found cleistogamous panicles in the lower sheaths of a plant from Benton County, Oklahoma.
Culms tufted, 2-7 dm, slender, stiff and strictly erect, somewhat bulbous-thickened at base or with bulb-like offsets; ligule 0.5 mm or less; blades erect or nearly so, flat or involute, 1-2 mm wide; panicle very slender and spike-like, the appressed lateral branches 5-15 mm; glumes lance-subulate, subequal, 1.7-2.8 mm; lemma 2.8-4.1 mm, slender, acuminate, awnless, minutely pubescent on the back, otherwise glabrous. Prairies and open hillsides, in dry or gravelly soil; Alta. to N.M., e. to Mich., O., Ky., and Mo.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.