Plants perennial; loosely matted. Culms 5-45 cm, arising from the bases of old depressed culms, compressed-keeled, developing branches below the lower leaf nodes; internodes mostly glabrous, sometimes minutely puberulent below the nodes. Sheaths longer than the internodes, keeled, keels scabridulous, not becoming papery or spirally coiled when old; ligules 0.5-1.5 mm, membranous, truncate to obtuse, erose, without lateral lobes; blades 1-15 cm long, 0.8-2 mm wide, flat to conduplicate, smooth or scabridulous abaxially, hirtellous adaxially, midveins thickened and whitish proximally. Panicles 2-20 cm long, (0.2)2.5-6 cm wide, diffuse; primary branches 0.4-6 cm long, about 0.1 mm thick, ascending, diverging 10-60° from the rachises, naked basally; pedicels 0.2-7 mm, glabrous. Spikelets 1.3-2.1 mm, dark purplish to plumbeous, occasionally with 2 florets. Glumes equal, 0.4-1.3 mm, glabrous, 1-veined, apices scabrous, acute to obtuse, sometimes erose or notched, unawned; lemmas 1.2-2 mm, oblong-elliptic, dark purplish to plumbeous, glabrous, faintly 3-veined, apices acute to obtuse, unawned; paleas 1.3-2.1 mm, oblong-elliptic, glabrous, acute to obtuse; anthers 0.6-0.9 mm, dark purple. Caryopses 0.6-0.8 mm, ovoid, brownish. 2n = 42.
Muhlenbergia uniflora grows in bogs, wet meadows, and lake shores in sandy or peaty, often acidic, soils, at elevations of 0-650 m. It is native to eastern North America, but was collected once in British Columbia, probably having been introduced from ship ballast, and was recently collected from a commercial cranberry bog in Oregon. The collection from Texas may also be an introduction.
Culms tufted, 2-4 dm, very slender, often decumbent and rooting at the base; sheaths and blades glabrous or nearly so, the latter flat or concave, rarely over 1 mm wide; ligule membranous, usually erose, 0.5-1.5 mm; infl slender but open, a fourth to half as long as the entire shoot; spikelets drab, ellipsoid, occasionally 2-fld, on pedicels mostly more than twice as long; glumes ovate, acute or obtuse, the second barely longer than the first and ca half as long as the spikelet; lemma acute, 1.2-2 mm, awnless; 2n=ca 42. Moist or wet, sandy or peaty soil, open meadows, and bogs; Nf. to w. Ont. and n. Mich., s. to N.J. (Sporobolus u.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.