Distribution: Known from the Puget Sound lowlands in Washington; south-central U.S., and in scattered locations in central and northeastern U.S.

Habitat: Pond and lake margins.

Flowers: June-August

Origin: Introduced

Conservation Status: Not of concern

Herbaceous stoloniferous perennials with floating leaves, up to 150 cm, corms present.

Submersed or emersed, margins entire; leaves under water phyllodial, sessile, flattened above and beneath, up to 26 cm long and 0.5 cm broad; leaves above water petiolate, petioles somewhat triangular and 21-70.5 cm long, blade linear-ovate to ovate, 4.6-16.4 cm long and 0.7-6.1 cm broad.

Inflorescences bracteate racemes with 3-9 whorls, above water, 2.5-10 cm long and 2-4.5 cm broad; peduncles 22-60 cm long; bracts connate greater than ¼ total length, lanceolate, 2-5.5 mm, delicate, not papillose; fruiting pedicels spreading to bending backwards, cylindric to 0.5-3 cm; flowers imperfect, to 1.8 cm in diameter; sepals 3, curving backward to spreading, not encasing the flower or fruiting head, persistent; petals 3, white, deciduous; filaments widened, longer than anthers, pubescent; anthers 2-chambered, splitting longitudinally; pistillate flowers pedicellate, sterile stamens absent.

Fruiting heads 0.7-1.2 cm in diameter; achenes oblanceoloid with no abaxial keel, 1.2-2 mm long and 0.8-1.2 mm broad, beaked; faces tuberculate, wings 0, glands 0; beak lateral, horizontal to erect, 0.3-0.6 mm.