About Bidens aristosa (Michx.) Britton
Bidens aristosa (Michx.) Britton is an herbaceous annual flowering plant. It usually reaches 1 to 2 feet in height, though it can grow as tall as 5 feet. Its leaves are borne on petioles that measure 1 to 3 cm long. Leaf blades range from lanceolate to lance-linear in shape, and are laciniately pinnatisect. The plant produces numerous yellow flower heads, each containing 5 to 10 ray florets and 12 to 40 disc florets. Its fruits are dry cypselae that bear barbs; these barbs catch on animal fur or human clothing, which helps the plant disperse its seeds. Bidens aristosa occurs in Alabama, Arkansas, the District of Columbia, Illinois, Indiana, Kentucky, Louisiana, Maryland, Michigan, Minnesota, Missouri, New York, North Carolina, South Carolina, Tennessee, Texas, Virginia, and Wisconsin in the United States, as well as in Ontario (Canada), France, Great Britain, and India. It is most likely native to the Central United States, and has been introduced to Eastern United States, Central Canada, France, Great Britain, and India. The first recorded sighting of Bidens aristosa in the eastern United States was along the Potomac River near Glen Echo, Maryland in 1902. The species is likely spread through the import of food crops or wool products. It grows in marshes, meadows, pine forests, and disturbed sites, at elevations between 0 and 300 metres above sea level.
