Plants perennial; cespitose, sometimes rhizomatous. Culms 30-200 cm, basal internodes occasionally globose. Sheaths open, not overlapping; auricles absent; ligules membranous, sometimes ciliate; blades flat or convolute. Inflorescences terminal, narrow panicles; branches spreading until after anthesis, then becoming loosely appressed to the rachises. Spikelets pedicellate, laterally compressed, with 2 florets, lower florets staminate, upper florets pistillate or bisexual, a rudimentary floret occasionally present distally; rachillas pubescent; disarticulation above the glumes, the florets usually falling together, rarely falling separately. Glumes unequal, hyaline, unawned; lower glumes less than 3/4 the length of the upper glumes, 1- or 3-veined; upper glumes 3-veined; calluses short, blunt, pubescent; lower lemmas membranous, 3-7-veined, acute, awned below midlength, awns twisted and geniculate; upper lemmas membranous to subcoriacous, glabrous or hairy, 7-veined, acute, usually unawned, sometimes awned from near the apices, awns short, straight, rarely awned similarly to the lower lemmas; paleas subequal to the lemmas, 2-veined, 2-keeled, keels scabrous or hairy, apices notched; lodicules 2, free, linear, membranous, glabrous, entire; anthers 3, 3.4-6.5 mm; ovaries pubescent. Caryopses shorter than the lemmas, concealed at maturity, not grooved, dorsally compressed to terete, hairy; hila long-linear, x = 7.
Conn., N.J., N.Y., Wash., Del., D.C, Wis., W.Va., Pacific Islands (Hawaii), Mass., Maine, N.H., R.I., Vt., B.C., N.B., Nfld. and Labr. (Labr.), N.S., Ont., Que., Wyo., N.Mex., La., N.C., Nebr., Tenn., Pa., Calif., Nev., Va., Colo., Md., Alaska, Ala., Ark., Ill., Ga., Ind., Iowa, Ariz., Idaho, Mont., Oreg., Ohio, Utah, Mo., Minn., Mich., Kans., Miss., S.Dak., Ky.
Arrhenatherum is a Mediterranean and eastern Asian genus of six species; one has become established in North America.