Plants annual and tufted, or perennial and rhizomatous. Culms 20-150 cm, sometimes tuberous at the base, erect. Leaves mostly cauline; sheaths open, glabrous, ribbed; auricles absent; ligules membranous, acute; blades flat, glabrous. Inflorescences dense, spikelike panicles; branches 1-sided, racemosely arranged, secondary branches few, at least some branches longer than 1 cm, with closely imbricate spikelets; disarticulation below the glumes, the spikelets falling entire. Spikelets laterally compressed, circular, ovate or obovate in side view, subsessile, with 1-2 florets; rachillas not prolonged beyond the base of the distal floret. Glumes subequal, slightly shorter than the lemmas, inflated, keeled, D-shaped in side view, unawned; calluses blunt, glabrous; lemmas lanceolate, inconspicuously 5-veined, unawned; paleas subequal to the lemmas; lodicules 2, free; anthers 3; ovaries glabrous. Caryopses shorter than the lemmas, concealed at maturity, x = 7.
Wash., Wis., Wyo., N.Mex., N.Y., Pa., Calif., Nev., Colo., Alaska, Ill., Iowa, Ariz., Idaho, N.Dak., Nebr., S.Dak., Maine, Ohio, Utah, Mo., Minn., Mich., Kans., Mont., Alta., B.C., Greenland, Nfld. and Labr. (Nfld.), Man., N.B., N.S., N.W.T., Nunavut, Ont., P.E.I., Que., Sask., Yukon, Oreg.
Beckmannia is a genus of two species: an annual species usually with one fertile floret per spikelet that is native to North America and Asia, and a perennial species with two fertile florets per spikelet that is restricted to Eurasia.
"decumbent" is not a number.