Parthenium integrifolium (wild quinine)

Parthenium integrifolium, commonly called wild quinine, is a perennial herb native to the central and eastern United States. It grows in prairies, open woods, glades, and other sunny habitats. The branching upper stems carry flat-topped clusters of small white composite flower heads that remain firm as they mature. Despite its common name and a history of traditional use, it is not the source of the antimalarial compound quinine. Photographed in Florida.