Plants annual or perennial; cespitose, sometimes rhizomatous. Culms 50-300+ cm, erect, nodding or clambering, unbranched; nodes densely pubescent, particularly in young plants. Leaves not aromatic; ligules membranous, glabrous or pubescent; blades flat, involute, or folded. Inflorescences terminal, secund or equilateral panicles with evident rachises and numerous branches, not subtended by modified leaves; branches capillary, rebranching, with many rames, not subtended by modified leaves; disarticulation in the rames, beneath the sessile spikelets. Spikelets sessile, subtending a hairy pedicel (2 pedicels in the terminal spikelet units), dorsally compressed. Calluses blunt or sharp; glumes coriaceous; lower glumes pubescent, 5-9-veined, acute; upper glumes slightly longer, usually glabrous, 5-veined, truncate; lower florets reduced to hyaline lemmas; upper florets bisexual, lemmas hyaline, bifid, awned from the sinuses; awns usually once- or twice-geniculate, often spirally twisted, shortly strigose, brownish; anthers 3; ovaries glabrous. Caryopses flattened. Pedicels 3-6.5 mm, slender, not fused to the rame axes; pedicellate spikelets absent. x = 10. Name from Sorghum and the Latin suffix astrum, a poor imitation of, alluding to its similarity to Sorghum.
Spikelets in pairs, one perfect, sessile, and subterete, the other represented only by its pedicel (2 such pedicels flanking the terminal spikelet of a raceme); glumes coriaceous, the first one hirsute, clasping or enclosing the glabrous or ciliate second one; lemmas 2, small, thin and hyaline, the lower one empty (sometimes nearly obsolete), the upper fertile and ending in a bent, twisted awn; erect perennials with elongate blades tapering to the base, the sheaths auricled at the summit; panicle slender, its ultimate branches bearing short, disarticulating racemes of 1-5 pairs of spikelets. 12, warm Amer. and Afr.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.