Perennial, loosely tufted, with long creeping rhizomes. Culms 50–150 cm tall, 2–3 mm in diam. Leaf sheaths scabrid on veins; leaf blades flat, thin, 10–20 cm × 4–12 mm, abaxial surface strongly scabrid on veins, adaxial surface smooth; ligule 2–5 mm. Panicle linear-oblong in outline, very dense with many crowded spikelets, interrupted below, 10–20 cm, 1-sided; branches erect, appressed to main axis, up to 5 cm. Spikelets broadly elliptic to obovate, 10–14 mm, fertile florets 2(or 3), terminal sterile lemmas gathered into globular cluster; glumes dark purple or white at maturity, oblanceolate-oblong to ovate, subequal, 7–11 mm, papery, 5–7-veined with connecting veinlets, both acute or obtuse; lemmas oblanceolate-oblong, lowest 8–11 mm, 7-veined, additional intermediate veins in lower half, scaberulous, apex obtuse, acute or minutely mucronate; palea 2/3 lemma length, keels ciliolate. Anthers 1.8–2.5 mm. Fl. and fr. Jun–Aug. 2n = 18.
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