Distribution: Occurring on both sides of the Cascades crest in Washington; British Columbia to Oregon, east across the northern U.S. and Canada to the Atlantic Coast.

Habitat: Shorelines of major rivers, wetlands, and ponds.

Flowers: July-September

Origin: Introduced from Eurasia

Growth Duration: Perennial

Conservation Status: Not of concern

Pollination: Bees, flies

Plants of fresh water, the stems to 150 cm long.

Leaves linear, to 2.7 m long, the blade triangular at the base, submersed, emersed or floating.

Inflorescence an umbel with 20-25 flowers on a triangular scape up to 150 cm long; bracts 3, subtending the umbel; pedicles 4-10 cm; flowers 2-2.5 cm wide; outer 3 tepals elliptic, 6-7.5 mm long and 2-2.5 mm wide; inner 3 tepals oblanceolate, 9-11.5 mm long and 4.5-6 mm wide; tepals light purple with darker purple veins; stamens 3 pairs opposite outer tepals and 3 opposite inner tepals; pistils pink.

Follicles leathery, 1 cm long.