Distribution: Currently only known from King County in Washington; Alaska, where native, to British Columbia, where also introduced.
Habitat: Marshy areas, sometimes largely submerged.
Flowers: June-September
Origin: Introduced from Eurasia and Alaska
Growth Duration: Perennial
Conservation Status: Not of concern
Pollination: Bees, flies
Scapose perennials, the scapes up to 12 dm. tall, longer than the leaves.
Leaves all basal, long-petiolate, the blades broadly lanceolate to ovate, 5-15 cm. broad, rounded to cordate at the base.
Flowers in much-compounded, bracteate, terminal panicles, the panicles branches in 2-6 whorles along the axis, the lower branches with 2 or more secondary branchlets or pedicles; sepals 3, 3-4 mm. long, greenish; petals 3, strongly pinkish- to purplish-tinged, 4-6 mm. long; stamens 6, opposite the petals; pistils 10-20 in a single whorl; styles 0.7-1.4 mm. long, slender, straight, nearly terminal on the ovary, persistent.
Achenes obovate, 2.5-3 mm. long.
Very similar to A. triviale, differing in flower color, and the longer, slender, straight style terminal on the ovary.
PNW Herbaria: Specimen records of Alisma plantago-aquatica in the Consortium of Pacific Northwest Herbaria database
WA Flora Checklist: Alisma plantago-aquatica checklist entry
OregonFlora: Alisma plantago-aquatica information
E-Flora BC: Alisma plantago-aquatica atlas page
CalPhotos: Alisma plantago-aquatica photos