Culms 48-131 cm, glabrous. Sheaths, collars, and auricles glabrous or pubescent; ligules 0.2-1 mm; blades 24-72 cm long, 6-18 mm wide, abaxial surfaces glabrous or scabridulous, adaxial surfaces similar or pubescent, margins usually scabridulous, rarely smooth. Panicles 5-30 cm, with 4-33 spikelets. Spikelets 7-17 mm, oblong to ovate, with (2)3-5(7) florets. Glumes green to stramineous; lower glumes 1.7-3.7 mm long, 0.3-0.6 mm wide in profile, 1-3-veined; upper glumes 2.2-5.2 mm long, 0.75-1.5 mm wide in profile, (3)5-veined; calluses glabrous; lemmas 3.7-7.5 mm, widest near or above the middle, obovate or elliptic in profile, abruptly tapering, apices sharply cuspidate; paleas glabrous, keeled, apices usually bifid, rarely truncate, sinuses 0.05-0.3(0.5) mm deep; anthers 1.4-2 mm. Caryopses 4.1-6 mm long, 1.8-2.5 mm wide, broadly elliptic to obovate in outline, narrowing abruptly to a bottlenose-shaped beak, usually smooth, occasionally wrinkled, shiny, usually straw-colored, with occasional brown areas basally. 2n = 60.
Kans., Nebr., Okla., W.Va., Pa., Tex., Md., Ind., S.Dak., Minn., Ky., Mich., Ohio, Wis., Tenn., N.Y., Va., Ark., Ill., Ont., Iowa, Mo.
Diarrhena obovata is restricted to the Flora region, growing in rich woodlands from South Dakota to Ontario and New York and south to Texas, Tennessee, and Virginia. It is most common in the prairie states.