Distribution: Chiefly east of the Cascades in Washington; British Columbia south to Baja California, east over nearly all of temperate North America.
Habitat: Moist, often waste ground, especially along river banks.
Conservation Status: Not of concern
Usually glabrous, prostrate annual, with dichotomous, freely-branched stems up to 3 dm. long, forming mat-like patches.
Leaves in whorls of 4-6, linear-oblanceolate to obovate, 10-30 mm. long and 1-3 mm. wide, narrowed to short petioles.
Flowers greenish, single in the leaf axils, several per node; pedicles slender, 3-10 mm. long; sepals 5, distinct, persistent, about 2 mm. long, white on the inner surface, prominently 3-nerved; corolla none; stamens usually 3; styles 3, less than 0.5 mm. long.
3-celled capsule, 3-4 mm. long.