Rhizomes creeping, long, slender. Culms solitary at nodes of rhizome, distantly arranged in a row, dark green, 7-35 cm tall, 0.8-1.2 mm thick, terete, clothed at base with 1 or 2 bladeless short leaf sheaths. Leaf sheaths pale brown, 1-5 cm, hyaline, mouth obliquely truncate. Involucral bract 1, erect, culmlike, apex subulate. Inflorescence generally a single pseudolateral spikelet. Spikelet sessile, greenish straw-colored, oblong to broadly narrowly ovoid, 4-6 × 2-3 mm, densely many flowered. Glumes pale yellow with some brown lines, oblong to elliptic, 4-4.5 × 1.8-2 mm, membranous, keel green, margin white hyaline, apex acute to obtuse. Perianth bristles 4 or 5, as long to 2 × as long as nutlet. Stamens 2 or 3; anthers linear, ca. 2.5 mm. Style 4-5 mm; stigmas 2. Nutlet black, obovoid to ellipsoid, 1.7-2.2 × 1.2-1.8 mm, plano-convex, shiny. Fl. and fr. Jul-Oct. 2n = ca. 60.
Marshy places; near sea level. Guangdong, Taiwan, Zhejiang [Japan, Russia (Far East)].