Plants perennial; rhizomatous, not cespitose. Culms 40-120 cm tall, less than 2 mm thick, erect; internodes mostly pubescent, retrorsely hirsute to strigose below the nodes. Sheaths mostly glabrous, usually pubescent near the base, scabridulous distally; ligules 0.4-1.2 mm, membranous, truncate, ciliolate; blades 6-20 cm long, 4-10(15) mm wide, flat, glabrous and smooth abaxially, occasionally scabridulous adaxially. Panicles usually terminal, 10-33 cm long, 0.2-0.8 cm wide, exserted; branches 1-10 cm, ascending to appressed; pedicels 1-6 mm, strigose. Spikelets 2.6-4.5 mm, overlapping the next spikelet on the branch by 1/4 of its length. Glumes subequal, 1.3-3 mm, shorter than the lemmas, 1-veined (lower glumes rarely 2- or 3-veined), tapering from near the base, bases overlapping, apices scabridulous, acute, unawned or awned, awns to 1 mm; lemmas 2.6-4.5 mm, lanceolate to narrowly lanceolate, usually pubescent on the calluses, lower 1/3 of the midveins, and margins (hairs sometimes restricted to the callus), hairs shorter than 1.2 mm, apices acute or acuminate, usually awned, awns to 12 mm; paleas 2.6-4.5 mm, lanceolate to narrowly lanceolate, shortly pilose on the lower portion, apices acuminate; anthers 1.1-2.2 mm, yellowish. Caryopses 2-2.3 mm, fusiform, brown. 2n = 40.
Conn., N.J., N.Y., W.Va., Del., D.C., Wis., Ont., Que., Nebr., Okla., N.H., Tenn., N.C., S.C., Pa., R.I., Va., Ala., Mass., Vt., Ark., Ill., Ga., Ind., Iowa, Md., Ohio, Mo., Mich., Miss., Ky.
Muhlenbergia tenuiflora grows only in the Flora region, usually being found on sandy or rocky slopes derived from sandstone, chert, or limestone formations, in mixed hardwood and oak-hickory forests, at elevations of 40-1500 m. It resembles the Asiatic species M. curviaristata (Ohwi) Ohwi.