|Mary E. Barkworth|
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,
blades usually flat or folded. Inflorescences false panicles
with numerous inflorescence units; peduncles with 2 rames in digitate
rames with naked, often deflexed bases, axes without a translucent
median groove; disarticulationin the rames, beneath the bisexual
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
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,
upper florets bisexual, awned from between the teeth of the bifid
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.
Spikelets with whitish to dark yellow hairs ..... 1. H. hirta
Spikelets with reddish hairs ..... 2. H. rufa
1. Hyparrhenia hirta (L.) Stapf
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
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.