Plants annual. Culms 30-100 cm; nodes pubescent, hairs appressed.
Sheaths with ciliate margins; ligules ciliate; blades to
12(25) cm long, to 10(20) mm wide, flat, hispid on both surfaces. Panicles
3-18 cm, loosely spicate, interrupted, often purple; rachises hispid; bristles
1-3, 5-15 mm, flexible, antrorsely scabrous. Spikelets 1.5-2.2 mm. Lower
glumes about 1/3 as long as the spikelets, distinctly 3-veined, lateral veins
coalescing with the central veins below the apices; upper glumes nearly
equaling the upper lemmas, obtuse, 5-veined; lower lemmas equaling the
upper lemmas; lower paleas about 1/3 as long as the lower lemmas, narrow;
upper lemmas finely and transversely rugose; upper paleas similar
to the upper lemmas. 2n = unknown.
Setaria grisebachii is the most widespread and abundant native annual species
of Setaria in the southwestern United States. It grows in open ground and
extends along the central highlands of Mexico to Guatemala, usually at elevations
of 750-2500 m. The specimens from Maryland were collected on chrome ore piles;
the species is not established in the state.
FNA 2003, Gould 1980
Common Name: Grisebach's bristlegrass Duration: Annual Nativity: Native Lifeform: Graminoid General: Annual grass, 15-50 cm tall; stems often geniculate-spreading and branching below; nodes microscopically pilose; internodes glabrous or pubescent. Vegetative: Sheaths densely ciliate, pubescent or pilose on collar; blades to 20 cm long, thin, flat, 4-10 mm broad; ligule hairy. Inflorescence: Panicle 3-15 cm long, typically loosely flowered and tapering to a point, often lobed or interrupted below, with branches to 2 cm long; occasionally the panicle is contracted and dense-flowered; bristles 5-15 mm long, flexuous, scabrous, green or purplish, 1-3 below each spikelet; spikelets 2 mm long; glumes strongly nerved, blunt, the first very short, the second equaling or slightly shorter than sterile and fertile lemmas; fertile lemmas and paleas finely cross-wrinkled. Ecology: Found on rocky slopes, washes, and in open woodlands; 2,000-6,500 ft (610-1981 m); flowers August-November. Distribution: AZ, NM, TX and OK; south to s MEX and S. Amer. 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. grisebachii is distinguished by being an annual with densely ciliate sheaths; loose, interrupted inflorescences which taper toward the apex; 1-2 bristles below each spikelet; and finely rugose (wrinkled) lemmas. Ethnobotany: Unknown Etymology: Setaria is from Latin saeta, a bristle or hair, while grisebachii is named for August Heinrich Rudolf Grisebach (1814-1879) a German botanist and phytogeographer. Synonyms: None Editor: SBuckley 2010, FSCoburn 2014, AHazelton 2015