Bouteloua barbata is a species of grass known by the common name six-weeks grama. It is native to North America, where it occurs in the southwestern United States and south to Oaxaca in southern Mexico. It may occur in Montana. It is also present in Argentina. This species is an annual or perennial grass producing tufts of stems up to 30 to 75 cm (12 to 30 in) long, lying prostrate, spreading, or standing erect. The inflorescence has up to 11 branches, each a dense row of up to 40 spikelets. The fruit weighs about 0. 03 milligrams. This lightweight seed is dispersed on the wind and by animals. It is annual or perennial, sprouting from seed or from its root crown after summer rainfall. Flowering usually begins around July and lasts until October. There are three varieties of this species. The var. barbata is an annual plant with decumbent stems that may root at stem nodes, var. rothrockii, sometimes considered a separate species, is perennial with erect stems, and var. sonorae, which is limited to northern Mexico, spreads via stolons.