Distribution: Alaska to Maine, south to California and New Mexico in the west and West Virginia in eastern United states
Habitat: Standing or running water
Flowers: June - August
Conservation Status: Not of concern
Aquatic, herbaceous perennials from slender rhizomes, the slender stems freely branching, sub-terete, up to 2 m. long.
Leaves alternate, the submersed leaves sessile, linear to lanceolate or oblanceolate, 3-9 cm. long and 3-10 mm. broad, 3- to 7-nerved; floating leaves long-petiolate, elliptic to oblong-elliptic, 2-5 cm. long and 1-2 cm. broad, 13- to 19-nerved; stipules open, firm, up to 3 cm. long.
Flowers perfect, in 6-10 crowded whorls, in spikes 1.5-2.5 cm. long on peduncles 4-10 cm. long, stout, thickened upward; perianth of 4 clawed segments, each with an upturned, oval blade; stamens 4, fused with the claws; pistils 4, sessile.
Achenes obliquely obovoid, 2-2.8 mm. long including the short stylar beak, the dorsal keel well developed, the lateral ones obscure.