Distribution: Occurring chiefly east of the Cascades crest in Washington; British Columbia to Mexico, east to the Atlantic Coast.

Habitat: Sandy river banks and other disturbed, seasonally moist areas.

Flowers: July-September

Origin: Introduced

Growth Duration: Annual

Conservation Status: Not of concern

Pollination: Wind

Prostrate, widely matted annual, the culms solid.

Sheaths open, keeled, glabrous; ligules 1-1.5 mm. long with a fringe of hairs 2-4 times as long as the basal membrane; blades flat or folded, 2-6 mm. broad.

Inflorescence a crowded raceme of 5-10 spiny burs; spikelets 2-flowered, usually 2 per bur, 5-6 mm. long, tightly enclosed within and deciduous with the burs; lower flower sterile, upper flower perfect; burs finely pubescent, the spines numerous, flattened, 4-6 mm. in diameter; glumes narrow, shorter than the lemmas.