Description from Flora of China
Annuals. Rhizomes absent. Culms tufted, 2.5-15 cm tall, slender, smooth. Leaves as long as or shorter than culm; sheath rust-colored, thinly membranous, glabrous, mouth obliquely split; leaf blade capillary, 2.5-15 cm × 0.2-0.5 mm, involute to nearly flat. Involucral bracts 3-10, setaceous, basal 1 or 2 sometimes surpassing inflorescence. Inflorescence a simple or subcompound anthela, with fewer to numerous spikelets; rays 3-10, slender, unequal, spreading. Spikelets solitary, rarely 2 clustered, oblong, oblong-ovoid, or subglobose, 3-6 × 2-6 mm, many flowered. Glumes white or pale straw-yellow, oblong, oblong-ovate, or elliptic, ca. 1 mm (excluding awn), thinly membranous, 1-veined forming an abaxial green keel, apex blunt and awned. Stamens 1 or 2; anthers narrowly ovoid to oblong. Style basally slightly thickened; stigmas 2. Nutlet brown, oblong, shiny, with transversely hexagonal reticulation or sublinear horizontal lines, each edge bearing 5-9 caducous clavate glandular cells. Fl. and fr. Mar-Nov.
Field margins, wet grassy places by rivers, swampy places, pond margins; below 100 m. Anhui, Guangdong, Guangxi, Hainan, Heilongjiang, Hunan, Yunnan, Zhejiang [India, Indonesia, Japan, Korea, Laos, Myanmar, Papua New Guinea, Philippines, Russia, Sri Lanka, Thailand, Vietnam; Africa, N Australia, South America].