Plants annual. Culms 30-130 cm. Sheaths glabrous; ligules
ciliate; blades 4-10 mm wide, loosely twisted, adaxial surfaces with
papillose-based hairs basally. Panicles 3-15 cm, uniformly thick, erect,
densely spicate; rachises hispid; bristles 4-12, 3-8 mm, antrorsely
scabrous. Spikelets 2-3.4 mm, strongly turgid. Lower glumes about
1/3 as long as the spikelets, 3-veined, acute; upper glumes about 1/2
as long as the spikelets, 5-veined, ovate; upper florets often staminate;
lower lemmas equaling the upper lemmas; lower paleas equaling
the lower lemmas, broad; upper lemmas conspicuously exposed, strongly
transversely rugose. 2n = 36, 72.
Reports of Setaria nigrirostris (Nees) T. Durand & Schinz in North America have not been verified. It differs from S. pumila in
being a rhizomatous perennial with spikelets 3.5-5 mm long and bristles with
thickened tips (those of S. pumila are slender throughout). It is a native
of southern Africa.