Description from Flora of China
Rhynchospora glauca Vahl var. chinensis (Nees & Meyen ex Nees) C. B. Clarke; R. japonica Makino; R. longisetigera Hayata.
Perennials. Rhizomes very short. Culms tufted, erect, 25-60(-125) cm tall, slender, 3-angled, rigid, basally clothed with 1 or 2 bladeless sheaths, apically scabrous. Leaves basal and cauline, shorter than inflorescence; sheath 5-9 cm; ligule rust-colored brown, short, membranous; leaf blade narrowly linear, 1.5-2.5 mm wide, margin scabrous, apex acuminate. Involucral bracts leaflike, longer than inflorescence, basal ones sheathing, apicalmost one shortly sheathing or sheathless. Inflorescences paniculate, consisting of 3-5 corymbiform anthelae, mostly binate, suberect; peduncle exserted, sublaxly bearing 2-9 clusters of spikelets. Spikelets brown, narrowly ovoid, 7-8 mm, 2-5-flowered, base ± obtuse, apex acute. Glumes 5-8, brown to yellowish brown, elliptic-ovate to lanceolate-elliptic; basal 2 or 3 glumes empty; apical glumes broadly ovate to lanceolate-elliptic, membranous, 1-costate, apex mucronate to acuminate. Perianth bristles 6, antrorsely scabrous. Stamens 3; filaments slightly longer than nutlet and style base; anthers linear. Ovary obovoid; style filiform, base dilated; stigmas 2, shorter than style. Nutlet dark reddish brown, broadly ellipsoid-obovoid, 2-3.7 mm, biconvex, finely transversely wrinkled with longitudinally oblong epidermal cell; persistent style base narrowly conic, slightly shorter than or equaling nutlet. Fl. and fr. May-Oct.
Swamps, moist places, wet grasslands; 100-1400 m. Anhui, Fujian, Guangdong, Guangxi, Hainan, Hubei, Jiangsu, Jiangxi, Shandong [Japan, Myanmar, Sri Lanka, Thailand, Vietnam; Indian Ocean islands, Madagascar].