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.
Origin: Introduced from Eurasia
Conservation Status: Not of concern
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.