Eupatorium

Eupatorium is a genus of flowering plants in the aster family, Asteraceae, containing from 36 to 60 species depending on the classification system. Most are herbaceous perennials growing to 0.5–3 m (1.6–9.8 ft) tall. A few are shrubs. The genus is native to temperate regions of the Northern Hemisphere. Most are commonly called bonesets, thoroughworts or snakeroots in North America. The genus is named for Mithridates Eupator, king of Pontus.[3]

Eupatorium has at times been held to contain as many as 800 species,[4] but many of these have been moved (at least by some authors) to other genera, including Ageratina, Chromolaena, Condylidium, Conoclinium, Critonia, Cronquistianthus, Eutrochium, Fleischmannia, Flyriella, Hebeclinium, Koanophyllon, Mikania, and Tamaulipa.[5]

The classification of the tribe Eupatorieae, including species placed in Eupatorium in the present or past, is an area of ongoing research, so further changes are likely. What seems fairly certain by now is that there is a monophyletic group containing Eupatorium (about 42 species of white flowered plants in North America, Europe and Asia, but not South America) and the Joe-pye weeds (Eutrochium), and possibly others.[6]

Eupatorium are grown as ornamental plants, in particular in Asia.[7] A number of popular ornamental plants formerly included in Eupatorium have been moved to other genera, such as Bartlettina and Conoclinium.

Tobacco leaf curl virus is a pathogen occasionally affecting plants of this genus. The foliage is eaten by some Lepidoptera larvae, including those of Orthonama obstipata (The Gem).