Biology :
Perennial or sometimes seemingly annual herb 0,1-1 m tall, gregarious but not clump-forming; roots with white nut-like nodules turning brown; culms few, somewhat swollen at base, arising from rather thick scale-covered stolons; culms green, 1-3 mm Ø, triangular; leaves glossy green; sheath green to reddish-brown; blade linear, 10-40 cm long, 2-8 mm wide, ± M-shaped in cross-section; inflorescence a simple or compound anthela, primary branches 1-8, 0,5-12 cm long; spikelets in rather dense clusters, 3-15 per cluster, bright to golden to dark brown, ± lanceolate, ± flattened, 6-70 mm long.
Ecology :
Swamps; damp sites; riverbanks; drainage lines in coastal bush or forest glades; seasonally wet grassland; clay; sandy well drained soils; fallow fields; forest gallery; also dry places; margins of springs and streams; depression in wadi. Very variable species, particularly as regards the colour and size of the glumes. Cyperus rotundus is the most pestiferous plant in the world.