Plants summer or winter annuals or perennials; cespitose, sometimes shortly rhizomatous. Culms to 135(150) cm, erect, geniculate, or decumbent; nodes glabrous or pubescent. Sheaths open, pubescent or glabrous; auricles present or absent; ligules hyaline, truncate, erose; blades flat to more or less involute, more or less pubescent on both sides. Inflorescences usually spikelike racemes, sometimes spikes, all customarily called spikes, with 3 spikelets at each node, central spikelets usually sessile, sometimes pedicellate, pedicels to 2 mm, lateral spikelets usually pedicellate, pedicels curved or straight, sometimes all 3 spikelets sessile in cultivated plants; disarticulation usually in the rachises, the spikelets falling in triplets, cultivated forms generally not disarticulating. Spikelets with 1 floret; glumes awnlike, usually exceeding the floret. Lateral spikelets usually sterile or staminate, often bisexual in cultivated forms; florets pedicellate, usually reduced; lemmas awned or unawned. Central spikelets bisexual; florets sessile; rachillas prolonged beyond the floret; lemmas ovate, glabrous to pubescent, 5-veined, usually awned, rarely unawned; paleas almost equal to the lemmas, narrowly ovate, keeled; lodicules 2, broadly lanceolate, margins ciliate; anthers 3, usually yellowish. Caryopses usually tightly enclosed in the lemma and palea at maturity. 2n = 14, 28, 42. Name from the old Latin name for barley.
Spikelets 1(2)-fld, not disarticulating, borne in triads on opposite sides of the rachis, the lateral spikelets often pedicellate and sterile, the central one sessile and fertile; glumes elongate, awned or awn-like, setaceous throughout or widened at base, the 6 in each triad of spikelets forming a false invol to the florets; lemma of the lateral spikelets often reduced or abortive, that of the central spikelet indurate, obscurely veined, its rounded back turned away from the rachis, usually long-awned; rachilla prolonged behind the palea as a short bristle; grasses with mostly flat lvs, scarious, truncate ligules, and dense, bristly spikes which, except in H. vulgare, disarticulate at each joint. (Critesion) 35, widespread
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.