Distribution: Occurring chiefly west of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast where native.
Habitat: Wet places, often where disturbed, primarily at low elevations.
Origin: Introduced from Eurasia and eastern North America
Conservation Status: Not of concern
Annual, nearly glabrous throughout, 1-20 dm. tall.
Leaves simple (but appearing trifoliate), sharply serrate, usually deeply divided into 3 narrow lobes, the center one larger and wider, 3-15 cm. long.
Heads erect, rayless, or occasionally with rays up to 4 mm. long; outer involucral bracts 4-9, herbaceous, enlarged and leafy.
Achenes wedge-shaped, flat or compressed-quadrangular, brown or blackish to purplish, with persistent pappus of 2-4 awns.
The winged petioles of Bidens tripartita should separate it from the very similar B. frondosa.