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; sheaths mostly 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. Panicles usually 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. Spikelets pectinate, 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 segments 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.
Wis., Fla., Wyo., N.Mex., Tex., La., Md., Miss., N.Y., Nev., Colo., Kans., N.Dak., Nebr., Okla., S.Dak., Ark., Ga., Ill., Maine, Minn., Mont., S.C., Utah, Iowa, Ariz., Ohio, Mo.
Bouteloua hirsuta is a widespread species, with two subspecies that frequently hybridize in areas of sympatry (Wipff and Jones 1996).
|1||Rachilla segments subtending second florets with a distal tuft of hairs; culms erect from the base, usually unbranched||Bouteloua hirsuta subsp. pectinata|
|1||Rachilla segments subtending second florets without a distal tuft of hairs; culms usually decumbent and branched basally||Bouteloua hirsuta subsp. hirsuta|