Plants annual. Culms 20-80 cm, to about 1 mm thick, solid, branching above the base. Sheaths open; ligules of hairs; blades flat. Inflorescences terminal, panicles, 8-23 cm long, 0.8-2 cm wide, with pilose rachises; branches 0.5-1.5 cm, spikelets congested, shortly pedicellate, the pedicels subtended by a 3-10 mm, terete bristle; disarticulation below the glumes. Spikelets dorsally compressed, with 2 florets, lower florets usually sterile, upper florets bisexual. Lower glumes about 1/4 as long as the spikelets, 5-7-veined, subclasping; upper glumes slightly shorter than the spikelets, 11-19-veined, indurate at maturity, constricted at the base, auriculate above the point of constriction; lower lemmas longer than the glumes, membranous but somewhat indurate at the base; lower paleas usually present, short; upper lemmas indurate, finely transversely rugose, apiculate, margins clasping the paleas; upper paleas similar to the lemmas in length and texture; lodicules 2; anthers 3, purple; ovaries glabrous; style branches 2,free to the base. Caryopses ovate, plano-convex; embryos about 1/2 as long as the caryopses. x = 9. Name from the grass genus Setaria and the Greek opsis, appearance or likeness.

Setariopsis includes two species, both of which were thought to be endemic to Mexico until the recent discovery of the following species in Arizona (Reeder 2001).

1.   Setariopsis auriculata (E. Fourn.) Scribn.

Culms 20-70 cm, weak, erect or ascending, glabrous or with a few, short, appressed hairs on and immediately below the nodes. Sheaths mostly glabrous but with soft hairs near the ligule; ligules 1-1.5 mm; blades to 20 cm long, 5-15 mm wide, glabrous or with a few hairs on the collars. Panicles 8-16 cm long, 0.8-1.5 cm wide; branches 0.5-3.5 cm; bristles 3-10 mm, antrorsely barbed. Spikelets 3-3.5 mm, ovate, acute. Lower glumes about 1 mm long, 1.5 mm wide, inflated; upper glumes 2.7-3.2 mm, ovate, somewhat inflated, abruptly constricted below, margins resembling auricles, apices acute or obtuse; lower lemmas ovate-triangular, indurate in the lower 1/3 where the spikelet narrows; upper lemmas 2-2.5 mm, finely and transversely rugose, acute and apiculate; anthers 0.8-1 mm, purple. 2n = 18.

Setariopsis auriculata was recently found to be established in Arizona (Reeder 2001), growing in moist, shady habitats. Prior to this discovery, its range was considered to extend from northern Mexico to Nicaragua, Colombia, and Venezuela.