Native to warm temperate and tropical regions worldwide in wet places, presumably originally distributed only in the Old World.In the Hawaiian Islands,
naturalized on
Kaua`i, O`ahu, Maui, Hawai`i.
Habit
Annuals with purple fibrous roots; culms tufted in small or relatively large clumps, pale green, erect to slightly spreading, soft, trigonous, the angles acute, (10-)25-60 cm tall, 2-5 mm in diameter.
Leaves
Leaves numerous, slightly shorter than the culm, blades pale green, soft, linear, 2-6 mm wide, folded, gradually tapering to an acute apex; sheaths pale brown or yellowish brown.
Flowers
Corymbs simple or compound, 2-6 cm long and as wide, primary rays 3-9, unequal in length, 1-4 cm long, secondary ones, when present, up to 1 cm long, each ray tipped with a dark green or brownish green globose cluster of numerous spikelets, 5-15 mm in diameter; involucral bracts 2-3, up to twice as long as the corymb; spikelets 8-28-flowered, lanceolate to linear-lanceolate, compressed, 2-8 mm long, ca. 1 mm wide, rachilla not winged; glumes dark green, tinged purplish brown, membranous, laxly spaced, suborbicular, 0.5-0.8 mm long and as wide, faintly 3-nerved, the keel yellow, apex rounded; style ca. 1/2 as long as the achene; stigmas 3.
Fruit
Achenes yellow at maturity, ovoid-ellipsoid, trigonous, nearly equalling the glume.
