Distribution: Ocurring east of the Cascades crest in Washington; British Columbia to California, east across much of North America to the Atlantic Coast.
Habitat: Bottomlands and other moist, open, often disturbed areas.
Origin: Introduced from south-central Canada and the central U.S.
Conservation Status: Not of concern
Large, coarse annual up to 20 dm. tall.
Leaves long-petiolate, the blade broadly ovate, 5-20 cm. long and 2.5-20 cm. wide, coarsely and often doubly serrate, gradually reduced upward.
Heads numerous, nearly sessile, in a large, paniculiform inflorescence; involucre 1.5-3 mm. high, the 5 herbaceous outer bracts larger than the 5 membranous inner bracts; corollas of the pistillate flowers obsolete; staminate corollas tubular, greenish, with undivided style, the filaments attached to each other; receptacle small, chaffy throughout; pappus none.
Achenes compressed parallel to the involucral bracts.