Description from Flora of China
Perennial, infrequently annual. Culms usually tufted, often tall and robust. Leaf blades not aromatic, linear, midvein distinct, apex acuminate; ligule scarious. Inflorescence a compound spathate panicle, each ultimate spatheole subtending a peduncle bearing a pair of short racemes; spatheoles linear to ovate, often brightly colored; peduncle shorter or longer than spatheole, often bearded; raceme pairs 2- to many-awned, often reflexed at maturity. Each raceme of a pair supported on a short stalk ("raceme base") arising from the peduncle apex (termed "upper" and "lower" raceme base), these subequal or the upper longer, terete or flattened. Racemes with 0–2 pairs of homogamous spikelets below the fertile pairs, these resembling the pedicelled spikelets; pedicels and internodes slender. Sessile spikelet dorsally compressed or subterete; callus obtuse to pungent, bearded, its apex exposed; lower glume lanceolate to linear, leathery, convex, glabrous to villous, flanks rounded, incurving, keeled only near apex; upper glume boat-shaped, 3-veined, awnless; lower floret reduced to a hyaline lemma; upper lemma stipiform, 2-toothed, awned between the teeth; awn geniculate with hairy column. Pedicelled spikelet male or barren, narrowly lanceolate, slightly longer than the sessile, acute to aristulate.
As a genus Hyparrhenia is easy to recognize, with its short, paired racemes grouped in a spathate panicle, exposed callus tip below the sessile spikelet, and hairy awns. Identification of the species depends on a careful inspection of the details of the pairs of racemes ("raceme pairs"). Homogamous spikelets are pairs of male or barren spikelets, generally resembling the pedicelled spikelets, often found at the base of one or both racemes. Their number and position are relatively stable within a species and provide a useful aid to identification.
Sixty-four species: mainly in Africa, a few species extending to other tropical regions; five species in China.
(Authors: Chen Shouliang (陈守良); Sylvia M. Phillips)