Culms 7–17 m, 4–7 cm in diam., basally straight, apically slightly drooping; internodes 20–35 cm, obviously shorter and slightly swollen near base and sometimes inconspicuously pale green striped and purple streaked, glabrous; wall 1–2 cm thick; nodes with a ring of gray-white silky hairs below and above sheath scar, several basal nodes usually with short aerial roots, lower ones with a ring of silky hairs above sheath scar; branching from basal 3rd or 4th node up. Branches usually several to many, clustered at mid-culm and basal nodes, central 3 codominant; branchlets usually specialized into weak or tough thorns. Culm sheaths tardily deciduous, leathery, glossy when fresh, ribbed-striate when dry, glabrous or stiffly hairy at basal margins only, apex subtruncate or slightly asymmetrical, arched; auricles undulate, wrinkled, inflated outward, densely hispidulous or subglabrous abaxially, unequal; larger auricle slightly decurrent, orbicular or ovate, 3.5–4 × 1–1.5 cm; small ones oblong or ovate, ca. 3 × 1–1.5 cm; ligule 4–5 mm, margin nearly entire and densely fimbriate; blade persistent, erect, inflated outward, ovate to oval, base slightly narrowed and then extended toward both sides and joined to auricles, apex abruptly acuminate, sharply tipped. Leaf blade linear-lanceolate to lanceolate, usually 8–23 × 1–2 cm, both surfaces glabrous. Pseudospikelets linear, compressed, more than 2 cm; gemmiferous bracts 2–4; fertile florets 5 or 6, then 2 sterile florets; rachilla segments usually fistulose, ca. 2.5 cm, apex ciliolate. Glumes absent; lemma to 8.5 mm, abaxially glossy and glabrous, many veined, margins glabrous, apex obtuse or acute and finely tipped; palea slightly shorter than lemma, keels ciliate near apex, 2-veined between and scabrous on either side of keels, apex obtuse or sometimes emarginate; lodicules 3, subequal, ovate or obovate, ca. 1.5 mm, margins ciliate, apex obtuse. Anthers ca. 4 mm, apex obtuse. Ovary narrowly obovoid, apex thickened and scabrous; style very short, scabrous; stigmas 3. New shoots Oct, fl. Aug–Sep.
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A bamboo. The stalks are 7-17 m long and 4-7 cm wide. The internodes are 20-35 cm long.