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.