Plants perennial; rhizomatous or stoloniferous. Culms to 2.5 m, erect, glabrous, unbranched. Ligules of hairs; blades flat, becoming involute when dry, margins scabrous, tapering to an attenuate apex. Inflorescences terminal, simple panicles, exceeding the leaves; disarticulation below the glumes. Spikelets 8-50 mm long, 6-16 mm wide, ovate-elliptical to ovate-triangular, strongly laterally compressed, with 3-34 florets, lowest 2-8 florets sterile, remaining floret(s) bisexual. Glumes subequal, shorter than the adjacent lemmas, midveins keeled, serrate to serrulate, apices unawned; lemmas 3-9-veined, midveins keeled, serrate to serrulate, apices somewhat blunt to acute or mucronate, unawned; paleas, if present, from slightly shorter than to exceeding the lemmas, 2-keeled, keels winged, serrulate or ciliate; anthers 3; ovary glabrous; styles 1, with 2 style branches. Caryopses linear; embryos less than 1/2 as long as the caryopses. x = 10. Name from the Latin unione glumarum, united bracts, apparently a reference to the spikelets.

Spikelets 5-many-fld, flat, disarticulating below the glumes; glumes shorter than the lemmas, subequal, acute or slightly mucronate, 3-veined, compressed-keeled, the keel serrulate; lower 2-6 lemmas empty; lemmas acute and obtusish or slightly mucronate, 3-9-veined, compressed-keeled, the keel serrulate; palea shorter to longer than the lemma, 2-keeled; erect, rhizomatous or stoloniferous perennials, with numerous large, stramineous spikelets in open to narrow and strict infls; ligule a fringe of hairs. 2, the other from Baja Calif. to Ecuador.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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