Distribution: British Columbia south on both sides of the Cascades to Mexico; east over most of the United States.
Habitat: Shallow to rather deep water.
Flowers: June - August
Conservation Status: Not of concern
Aquatic, herbaceous perennials from slender rhizomes, the stems sub-terete, sparingly branched, up to 2 m. long.
Leaves alternate, the submersed leaves with petioles 2-10 cm. long, the blades lanceolate-elliptic, 10-20 cm. long and 1-2 cm. broad, thin; floating leaves leathery, long-petiolate, elliptic, 5-12 cm long and 2-4 cm. broad; stipules 4-8 cm. long.
Flowers perfect, in densely-flowered spikes with up to 15 whorles, 2-6 cm. long; peduncles thicker than the stems; perianth of 4 clawed segments, each with an upturned, oval blade; stamens 4, fused with the claws; pistils 4, sessile.
Achenes obovoid, 3-4 mm. long, with a sharp dorsal keel and prominent lateral keels.