Caespitose perennial, 40-90 cm; with tillers. Stem 2.5-4 mm diam., obtusely trigonous, smooth. Leaves equalling or longer than stem; sheaths up to 20 cm, yellow-brown, often with reddish tint, soft, mouth margin somewhat concave; blades to more than 80 cm, 4-7 mm wide, greyish green, keeled, margins slightly revolute, margins and keel smooth or slightly scabrous, apex long-attenuate, trigonous, scabrous or nearly smooth. Inflorescence a rounded anthelodium, 8-10(-20) cm diam., primary branches 5-10, up to 10 cm, spreading, bracts 3-5 foliose, up to 50 cm; secondary anthelodia up to 5 cm diam., rounded with 3-5 bracts up to 30 mm; tubular prophyll up to 15 mm, yellow-brown often with reddish tint, bi-nerved, nerves with flat, scabrous arista up to 4 mm; tertiary anthelodia may be present; cluster of spikes 7-16 mm, nearly globose, with from c. 30 to more than 50 spreading, spirally arranged spikes, occasionally two sessile closely together. Spikes 5-7.5 x 0.5-0.8 mm, terete, brown, with 7 glumes, lowest sterile, next three fertile; rachis widely winged; glume-like bract c. 1 mm, brown, acute; glume-like prophyll c. 0.8 mm; glumes 2-3 mm, with rounded back, brown or reddish brown, mid-nerve ending in rounded apex, sides nerved, margins narrowly scarious. Stamens 2. Nut 2.3-2.4 x 0.3-0.4 mm, trigonous, slightly curved, plano-convex, brown, with persistent style-base c. 0.4 mm, finely reticulate and papillose.

Distribution: From Pakistan and India to China and Taiwan, Malaysia; intr. to Reunion and Mauritius.

Fl. Per.: September-November.

Swamps; also weed, especially in rice fields.

Mariscus compactus (Retz.) Boldingh, Zakfl. Java: 77. 1916; Druce, Rep. Bot. Exch. Club Brit. Is. 1916: 634. 1917; C. dilutus Vahl, Enum. Pl. 2: 357. 1805; C. spinulosus Roxb., Fl. Ind. 1: 207. 1820; Mariscus micocephalus Presl, Reliq. Hank. 1: 182. 1830; C. B. Clarke in Hook.f., Fl. Brit. Ind. 6: 624. 1893; Koyama, Fl. of Taiwan 5: Pl. 1344. 1979 (as M. compactus). U. Kühn, in E. Häfliger, ed., Monocot weeds, 53. 1982 (as M. compactus).