[Wikipedia] Common Names, Medicinal & Culinary Uses: Its many English common names include black-jack,? beggarticks, hairy beggarticks, cobbler's pegs, devil's needles, hairy bidens, Spanish needle, farmers friend, Devils Pitchfork, hitch hikers and sticky beaks.
Although Bidens pilosa is primarily considered a weed, in many parts of the world it is also a source of food and alternative medicine. The leaves have a resinous flavor, are eaten raw or in stews or dried for storage. It is especially important in eastern Africa, where it is known as michicha.
During the Vietnam War, soldiers adopted the herb as a vegetable, which led to it being known as the "soldier vegetable". It is susceptible to hand weeding if small enough; even then it must be bagged, and thick mulches may prevent it from growing.
Extracts from Bidens pilosa are used in Southern Africa for malaria. (link added by Mary Ann Machi)