Cyperus compactus Retz.

Perennials. Rhizomes short. Culms scattered or sparsely tufted, 50-90 cm tall, stout, terete, with conspicuously transverse veins, basally with leaves, base slightly swollen. Leaves longer to slightly shorter than culm; sheath purplish red, cylindric, mostly to 10 cm, usually splitting from membranous part; leaf blade 5-9 mm wide, flat, with conspicuously transverse veins, abaxial midvein and margin spinulose. Involucral bracts 3-5, leaflike, much longer than inflorescence, obliquely spreading, abaxially midvein and margin spinulose. Inflorescence a compound anthela, lax to slightly dense; rays 7-9, suberect, mostly to 15 cm, unequal in length, stiff, each with 5-10 raylets; raylets obliquely spreading, usually ± short, mostly to only 2 cm. Spikes with many spikelets congested into nearly a globose to half-globose spike at apex of raylets, 0.8-3.5 cm in diam. Spikelets many, radially spreading, subulate, 0.5-1.8 cm × less than 1 mm, 3-12-flowered; rachilla wings white, hyaline. Glumes blood-red to reddish brown on both surfaces but abaxially green at middle, narrowly oblong, 3-4 mm, slightly shiny, 5-7-veined, apex obtuse to acute. Stamens 3; anthers broadly linear; connective prominent beyond anthers. Style of long to medium length; stigmas 3, slender. Nutlet yellowish brown to brownish, narrowly oblong, 1/2-3/5 as long as subtending glume, 3-sided, densely puncticulate, apex mucronate. Fl. and fr. Jun-Dec.

Swamps, wet rice-fields, swampy grassfields, coastal marshes, forest-edges, along ditches and river-banks, 0-500 m, sometimes up to 1000 m; often gregarious and then striking by the large, reddish brown inflorescences.