Plants annual; glabrous or hispid, hairs papillose-based. Culms 11-110 cm, erect to decumbent; nodes shortly hirsute or glabrous. Sheaths shorter than the internodes, greenish to purplish, glabrous or with papillose-based hairs, ciliate on 1 margin, glabrous on the other; collars hirsute;ligules 1.5-3.5 mm, of hairs; blades 3-30 cm long, 3-30 mm wide, flat, usually hirsute or sparsely pubescent, hairs papillose-based, sometimes glabrous, bases rounded to cordate-clasping, margins ciliate, cilia papillose-based, apices acute. Panicles 9-30 cm long, 5-8 cm wide, erect or nodding, partially included to well-exserted, rachises glabrous or sparsely hispid basally; primary branches usually alternate to opposite, divergent, secondary branches and pedicels confined to the distal 2/3; pulvini inconspicuous; secondary branchesappressed; pedicels 9-27 mm, appressed. Spikelets 1.9-4 mm long, 0.8-1 mm wide, ovoid to almost spherical, often reddish-brown, glabrous, veins prominent, scabridulous, apices abruptly acuminate. Lower glumes 1.3-2.4 mm, 1/2-3/4 as long as the spikelets, 3-5-veined; upper glumes 1.8-3.3 mm, 7-11-veined; lower florets sterile; lower lemmas similar to the upper glumes, 9-veined; lower paleas 0.4-0.9 mm; upper florets 1.5-2.4 mm long, 0.4-0.8 mm wide, ellipsoid, smooth or conspicuously papillate, shiny, stramineous, often with a lunate scar at the base.
Panicum hirticaule grows in rocky or sandy soils in waste places, roadsides, ravines, and wet meadows along streams. Its range extends from southeastern California and southwestern Texas southward through Mexico, Central America, Cuba, and Hispaniola to western South America and Argentina.