Rhizomes elongate, covered with shiny, coriaceous, scalelike leaves. Culms to 2.5 m. Sheaths entirely glabrous or pubescent at the throat; ligules 0.7-2 mm; blades to 90 cm long, about 12 mm wide. Panicles 20-80 cm long, 20-60 cm wide; branches to 35 cm, ascending to strongly divergent, lowermost branches sometimes reflexed. Spikelets 7-10.8 mm. Glumes straight; lower glumes 4.5-10.5 mm; upper glumes 6.4-10.1 mm; callus hairs 1/4-3/4 as long as the lemma; lemmas 6-10 mm, straight, pubescent, sometimes sparsely so, very rarely glabrous; paleas 6-8.3 mm, pubescent or glabrous; anthers 3-5.5 mm. 2n = 60.

Calamovilfa gigantea grows on sand dunes, prairies, river banks, and flood plains in the Rocky Mountains and central plains from Utah and Nebraska to Arizona and Texas.