Perennial. Culms tufted, fairly robust, usually erect, 80–130 cm tall, many-noded, glabrous. Leaf sheaths broad, papery, overlapping and concealing the nodes, keeled, papillose-pilose along margins; leaf blades linear, 10–20 × 0.5–1 cm, glabrous, apex acuminate; ligule 1–2 mm, usually with tawny hairs on back. Inflorescence axis 4–10 cm; racemes 5–20, 4–8 cm, ascending; spikelets normally paired, occasionally single but 2nd vestigial spikelet present; densely overlapping; rachis broadly winged, (1.5–)2–4 mm wide, purplish, margins scabrous with conspicuous close-set teeth; pedicels scabrous. Spikelets purple or pale green, broadly obovate, narrowed to base, lightly plano-convex, 2–2.5 mm, apiculate; upper glume and lower lemma membranous, 3-veined with laterals marginal, minutely crisped-pubescent; upper lemma pallid, as long as spikelet, punctulate-striate, subacute. Fl. and fr. Jul–Oct. 2n = 40, 50.
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