Distribution: Both sides of the Cascades in Washington; Alaska to Newfoundland, south to northwest California and North Carolina.
Habitat: Stream banks, marshes and peat bogs, mostly in the mountains, but descending to sea level west of the Cascades.
Conservation Status: Not of concern
Herbaceous, puberulent perennial from tubers with very slender rhizomes and stolons, the stems usually simple, 1-4 dm. tall.
Leaves opposite, nearly glabrous, all cauline and not much reduced upward, 2-8 cm. long and 0.6-3 cm. wide, narrowed to a short petiole, the margins coarsely and irregularly serrate-dentate.
Flowers in tight whorls in the leaf axils, sessile; calyx small, soft, obscurely nerved, the 5 ovate teeth acutish; corolla white or pinkish, 2.5-3.5 mm. long, surpassing the calyx, 4-lobed, nearly regular, the tube short; stamens 2, the upper pair (of the usual 4) obsolete.
Nutlets 4, the outer top margin toothed.