Kendrick L. Marr Richard, J. Hebda and Craig W. Greene†
Culms (85)90–120 cm. Sheaths smooth; collars glabrous; ligules (2)3–4(6) mm; blades (12)16–28(30) cm long, (2)6–8(12) mm wide, glaucous on both surfaces. Panicles (11)14–18(22) cm long, (1.5)2–3(3.5) cm wide; branches (2.5)5–7(7.5) cm. Spikelets (4)5(6) mm; rachilla prolongations with 1.5–2(3) mm hairs. Callus hairs 2(3) mm, 0.5–0.7 times as long as the lemmas; lemmas 3(4) mm, 1(2) mm shorter than the glumes; awns 3–3.5 mm, attached to the lower 1/10–3/10 of the lemmas; anthers 2–2.5 mm. 2n = 56.
Isolated populations of Calamagrostis porteri subsp. insperata grow from southern Missouri and Arkansas to Ohio and Kentucky. It is listed as possibly extirpated or of conservation concern in several states.