Stems slender, weak, annual, decumbent, or climbing over other plants by the numerous sharp, recurved prickles which arm its four prominent angles. Leaves lanceolate-sagittate or oblong-sagittate, 1 to 3 inches long, pointed at the apex, slightly rough margined, the lower leaves petioled, upper ones sessile or nearly so, prickly on the petioles and beneath on the midribs; ocreae oblique, not ciliate. Flowers in terminal heads or racemes, rose-colored or greenish; stamens usually eight in number; style three-parted.
In wet soil, Newfoundland and Nova Scotia to the Northwest Territory, south to Florida and Kansas. Flowering from July to September.
Memoir 15 N. Y. State Museum
Halberd-Leaved Tearthumb - Tracaulon arifolium