Plants perennial; cespitose. Culms 1.5-2(4) m, decumbent, geniculate, branching; nodes glabrous. Leaves green; sheaths glabrous; ligules 0.5-1.5 mm; blades 23-40 cm long, 7-12 mm wide, flat, glabrous. Panicles terminal, 15-22 cm long, 15-21 mm wide, fully exerted from the sheaths, flexible, drooping, green; rachises terete, puberulent. Fascicles 24-49 per cm; fascicle axes 0.4-0.5 mm, with 1 spikelet; most bristles only slightly longer than the spikelets; outer bristles 27-41, 2.4-8.5 mm; inner bristles 3-5, 6.2-11 mm, scabrous; primary bristles 7.6-11.8 mm, not noticeably longer than the other bristles, scabrous. Spikelets 5.2-6.6 mm, sessile; lower glumes 1.7-2.9 mm, 1-veined; upper glumes 4.5-6.3 mm, about as long as the spikelets, (7)9-veined; lower florets sterile; lower lemmas 4.8-6 mm, 7-veined, acuminate to attenuate, midvein excurrent for 0-0.6 mm; lower paleas absent; upper lemmas 4.9-6 mm, 5-veined, acuminate to attenuate, midvein excurrent for 0-0.6 mm; anthers 1.3-1.7 mm. 2n = 36.

Pennisetum nervosum is native to South America. It has been introduced in the Flora region, being known from populations adjacent to the Rio Grande River in Cameron and Hidalgo counties, Texas, and San Diego Couty, California.