Plants perennial; cespitose. Culms 20-100 cm. Sheaths compressed,
glabrous, margins villous distally; ligules 1-2.5 mm, ciliate; blades
8-25 cm long, 2-5 mm wide, flat or folded, scabrous on both surfaces. Panicles
6-15 cm, tightly spikelike, pale green; rachises scabrous or villous; bristles
usually solitary, 4-15 mm, ascending. Spikelets 2.2-2.8(3) mm, elliptical.
Lower glumes about 1/2 as long as the spikelets, 3-veined; upper glumes
from 3/4 as long as to equaling the florets, 5-veined; lower lemmas equaling
the upper lemmas, 5-veined; lower paleas 1/2-3/4 as long as the upper paleas,
lanceolate; upper lemmas apiculate, finely and transversely rugose; upper
paleas similar. 2n = 54, 68, 72.
Setaria leucopila grows in the southwestern United States and northern Mexico.
It is the most common of the perennial Plains bristlegrasses.
FNA 2003, Gould 1980
Common Name: streambed bristlegrass Duration: Perennial Nativity: Native Lifeform: Graminoid General: Tufted perennial grass, 20-100 cm, usually pale or glaucous; stems erect or geniculate from cespitose base, compressed, scabrous below panicle and nodes, often pubescent below nodes. Vegetative: Sheaths compressed-keeled, glabrous except near scabrous summit and keel, villous along upper margins; ligule 1-2.5 mm long, densely ciliate; leaf blades 2-5 mm wide, flat or folded, 8-25 cm long, scabrous on both surfaces or nearly glabrous beneath. Inflorescence: Densely flowered panicle, 6-15 cm long, pale green, columnar, often interrupted below, the axis scabrous or villous; bristles mostly solitary below each spikelet, 4-15 mm, ascending; spikelets 2-3 mm, elliptical, and 2-flowered, the first floret sterile or staminate, and the second floret fertile; lower glumes about 1/2 as long as the spikelets, 3-veined; upper glumes from 3/4 as long as to equaling the florets, 5-veined; sterile lemma and fertile lemma about equal; fertile lemma apiculate, finely rugose transversely. Ecology: Found in grasslands and open ground, from 3,000-7,000 ft (914-2134 m); flowers May-October. Distribution: sw US from AZ and UT east to TX and OK; south to s MEX and disjunct in South America. Notes: Setaria spp. have inflorescences with short, mostly contracted branches and single-seeded, hard spikelets subtended by persistent bristles that remain on the plant after the spikelets have fallen. S. leucopila is the main perennial Setaria of grasslands in the Southwest and is distinguished by being an often robust, erect perennial to 1 m, with leaves < 5 mm wide, columnar inflorescences 6-15 cm long, and spikelets resembling an elongated hemisphere (elliptical; see pic). S. macrostachya is nearly identical but differs by often being taller, having wider leaves (7-15 mm wide), usually longer inflorescences (10-30 cm) and spikelets which are more rounded on the back (subspherical). Ethnobotany: Unknown Etymology: Setaria is from Latin saeta, a bristle or hair; leucopila is from Greek leukos for bright, clear, or white, and Latin pilus, a hair. Synonyms: Chaetochloa leucophila Editor: SBuckley 2010, FSCoburn 2014, AHazelton 2015