Sp. Pl. 1: 372. 1753; Gen. Pl. ed. 5; 174, 1754.
Plants in fresh water to 2 m deep. Leaves emersed, submersed, or floating; blade triangular proximally, flattened distally. Inflorescences overtopping leaves; scape trianglular; bracts 3, subtending umbel. Flowers: tepals light pink-purple with darker purple veins; stamens in 2 cycles, outer cycle of 3 pairs opposite outer tepals, inner cycle of 3 opposite inner tepals; anthers ovoid; pistils pink. Fruits leathery, beaked.
Introduced; North America, Eurasia.