Distribution: Chiefly east of the Cascades; southern British Columbia to California, east to Colorado and Minnisota.
Habitat: Marshes and shores of streams and lakes; tolerant of alkali.
Conservation Status: Not of concern
Perennial herbs from tuberous rhizomes, the simple or branched, square stem 2-8 dm. tall, with spreading hairs on the angles.
Leaves opposite, all cauline, glabrous or scabrous above and glabrous below, numerous, 3.5-10 cm. long and 0.6-3.5 cm. broad, oblong-lanceolate, coarsely and evenly serrate, nearly sessile.
Flowers sessile, verticillate in the axils of scarcely reduced leaves; calyx with 5 firm, narrow, sharp-pointed lobes; corolla white, 3-5 mm. long, about equally 4-lobed; fertile stamens 2, barely exerted, sterile stamens 2, small, club-shaped; style 2-parted; ovary 2-celled, superior.
Nutlets 4, the outer apical margin truncate and irregularly toothed.