Bidens vulgata is an annual herb to 1.5 m tall, stems often reddish, smooth to hairy.
Leaves alternate, stalked, pinnate, leaflets 3-5, narrow, tip long-pointed, base wedge-shaped, margins toothed (sometimes lobed).
Flowers pale yellow, rays inconspicuous, disk flowers 40-60, heads hemispheric, 1-2.5 cm wide, outer bracts leaf-like 10-20, unequal, 1-4 cm long, loose, densely hairy, inner bracts 8-18, triangular, olive or brownish, about 1 cm long, flowers; Aug.-Oct.
Fruit dry, 1-seeded achenes, 0.6-1 cm long, 0.4-0.6 cm wide, flat, widest near top, with two soft spines (horn-like) to 0.6 cm long. Seeds eaten by birds, plants eaten by rabbits (Martin et al. 1951).
Wetland status: UPL.
Frequency in NYC: Very infrequent.
Habitat: Open, disturbed areas, most fill. Very similar to B. frondosa, which has smaller heads with fewer bracts.