Plants annual or perennial; cespitose, often with short rhizomes. Culms 30-350(400) cm, usually erect, much branched above the bases. Leaves not aromatic; ligules membranous, not ciliate; blades usually flat or folded. Inflorescences false panicles with numerous inflorescence units; peduncles with 2 rames in digitate clusters; rames with naked, often deflexed bases, axes without a translucent median groove; disarticulationin the rames, beneath the bisexual spikelets. Spikelets in sessile-pedicellate pairs, basal 1-2 pairs on each rame homogamous, morphologically similar to the heterogamous pairs, staminate or sterile, unawned, not forming an involucre, tardily deciduous, remaining pairs heterogamous. Heterogamous spikelet units: sessile spikelets dorsally compressed or subterete; calluses blunt to sharp, strigose; glumes equal, pubescent; lower glumes coriaceous, rounded, without keels, truncate to slightly bilobed; upper glumes narrower, shallowly keeled; lower florets sterile, reduced; upper florets bisexual, awned from between the teeth of the bifid lemma; awns usually present, to 3.5(19) cm, pubescent on the lower portion. Caryopses oblong, subterete. Pedicels slender, not adnate to the rame axes. Pedicellate spikelets usually slightly longer than the sessile spikelets, staminate or sterile, usually unawned, lower glumes sometimes aristulate. x = 10, 15. Name from the Greek hypo, under, and arrhen, masculine, referring to the pair of staminate spikelets at the base of the rames of some species.

Hyparrhenia is a genus of approximately 55 mostly African species. Two have been introduced into the Flora region, but only one is known to be established. Clayton (1969) provides a detailed discussion of the structure of the inflorescence.

1.   Hyparrhenia hirta (L.) Stapf
Thatching Grass

Plants perennial; cespitose but with short rhizomes. Culms 30-100 cm. Sheaths glabrous; blades 2-40 cm long, 1-3(4) mm wide. Peduncles 5-10 cm; rames 1-3.5(4) cm, 1 almost sessile, the other with a 5-10 mm base, both with 8-14 heterogamous spikelet pairs. Glumes of all spikelets densely pubescent, hairs to 0.3 mm, white to dark yellow. Sessile spikelets of homogamous pairs 4.9-5.6 mm; sessile spikelets of heterogamous pairs 4-4.5 mm; lemmas awned, awns 1-3.5 cm. Pedicellate spikelets 4.8-6.5 mm. 2n = 30, 44, 45.

Hyparrhenia hirta is native to southern Africa, where it grows on stony soils and is sometimes used for thatching. It has been cultivated in Texas and Florida, but is not currently known to be established in the Flora region. A report of its occurrence in Los Angeles County, California, has not been verified.

2.   Hyparrhenia rufa (Nees) Stapf
Jaragua Grass

Plants usually perennial; cespitose but with short rhizomes. Culms 30-350 cm. Sheaths glabrous; blades 30-60 cm long, 2-8 mm wide. Peduncles 0.7-7 cm; rames 1.5-2.5 cm, 1 almost sessile, the other with a 6-10 mm stalk, both with 7-14 heterogamous spikelet pairs. Glumes of all spikelets moderately densely pubescent, hairs reddish. Sessile spikelets of homogamous pairs 3-5.5 mm, sessile spikelets of heterogamous pairs 3.2-4.2 mm; lemmas awned, awns 2-3 cm. Pedicellate spikelets 3-5 mm. 2n = 30, 36, 40.

Hyparrhenia rufa is native to the Eastern Hemisphere tropics, but is now established in tropical America. It grows in ditches, pastures, swamps, and pine flatwoods, and along roadsides, in the southeastern United States.