boneset (bōnˈsĕt) [key] or thoroughwort thûrˈəwûrtˌ, –wôrtˌ, perennial North American herb ( Eupatorium perfoliatum ) of the family Asteraceae (aster family), having terminal clusters of small, chiefly white blossoms. Native Americans and settlers alike valued the plant for the bitter tea made from its leaves and flowers, for which it was often cultivated in gardens. The tea was used for treating colds, fever, and ague (whence the name agueweed). The herb is still sold for medicinal purposes. Other species of Eupatorium, most of which are American, are often called thoroughwort and occasionally boneset, e.g., the purple boneset, or joe-pye weed. Boneset is classified in the division Magnoliophyta, class Magnoliopsida, order Asterales, family Asteraceae.