Plants perennial. Culms 30-70 cm, usually erect, branching profusely
at the base; nodes glabrous or sparsely hispid. Sheaths keeled,
sparsely pubescent, margins ciliate distally; ligules to 1 mm, of hairs;
blades 15-30 cm long, usually less than 5 mm wide, densely pubescent on
both surfaces. Panicles 5-15 cm, slender, attenuate, interrupted, sparsely
flowered; rachises pubescent; branches mostly shorter than 10 mm,
villous; bristles usually solitary, 4-7 mm, antrorsely scabrous. Spikelets
about 2 mm, ovate-lanceolate. Lower glumes about 1/3 as long as the spikelets,
3-veined; upper glumes about 1/2 as long as the spikelets, 5-7-veined;
lower lemmas equaling the upper lemmas; lower paleas equaling the
upper paleas, broad; upper lemmas finely and distinctly transversely rugose;
upper paleas similar to the upper lemmas. 2n = unknown.
Setaria rariflora has its center of distribution in South America. It is
probably only recently adventive in North America, where it is known from Florida
and the West Indies.