Distribution: British Columbia to Newfoundland, south to California in the west and Alabama in the eastern United States, but absent from Nevada to Texas; common west of the Cascades in Washington
Habitat: Generally in fairly deep water
Flowers: June - August
Conservation Status: Not of concern
Aquatic, herbaceous perennials from slender rhizomes, the terete stems up to 4 mm. thick and 1 m. long, simple or sparingly branched above.
Leaves alternate, the submersed leaves short-petiolate, the upper ones 8-20 cm. long and 2-5 cm. broad, acute at both ends, folded, and sickle-shaped in outline, 25- to 45-nerved; floating leaves with long, stout petioles, the blades leathery, ovate to ovate-elliptic, acute or rounded at the base, 5-10 cm long and 2-4 cm. broad; stipules to 10 cm. long, free of the petiole.
Flowers perfect, in densely-flowered spikes on peduncles 7-15 cm. long; perianth of 4 clawed segments, each with an upturned, oval blade; stamens 4, fused with the claws; pistils 4, sessile.
Achenes obliquely ovoid, 4-5 mm. long, with a sharp dorsal keel and 2 lateral keels.