Plants perennial; densely or loosely cespitose, occasionally stoloniferous. Culms 15-75 cm, erect or decumbent, sometimes branched basally, sometimes branched aerially; nodes 3-6; internodes glabrous or sparsely to densely pubescent with papillose-based hairs. Leaves basal or mainly cauline; sheathsmostly glabrous, finely scabrous, or pubescent, pilose near the ligules; ligules 0.2-0.5 mm, of hairs; blades 1-30 cm long, 1-2.5 mm wide, flat to involute, papillose-based hairs often present on both surfaces, usually present on the bases of the margins. Paniclesusually with 0.7-18 cm rachises bearing 1-6 branches, the branches sometimes digitate; branches 10-40 mm, persistent, straight, with 20-50 spikelets, axes extending 5-10 mm beyond base of the terminal spikelets; disarticulation above the glumes. Spikeletspectinate, green to dark purple, with 1 bisexual floret and 1-2 rudimentary florets. Glumes acuminate or awn-tipped; lower glumes 1.4-3.5 mm; upper glumes 3-6 mm, midveins with papillose-based hairs; lowest lemmas 2-4.5 mm, pubescent, 1-3-awned, central (or only) awns 0.2-2.5 mm, not flanked by membranous lobes, lateral lobes acuminate, unawned or with awns no longer than the central awn; lower paleas ovate, unawned;anthers 2-3.4 mm, cream or yellow; rachilla internodes subtending second florets glabrous or pubescent, sometimes with a distal tuft of hairs; second lemmas 0.5-2 mm, bilobed, 3-awned, awns 2-4(6) mm; third lemmas, if present, minute, membranous scales, glabrous. Caryopses 1.5-2.6 mm. 2n = 20, 40, 50, 60; numerous dysploid numbers also reported.

Bouteloua hirsuta is a widespread species, with two subspecies that frequently hybridize in areas of sympatry (Wipff and Jones 1996).