[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.

The common names for the plants are all based on the previous usage of one species, Eupatorium perfoliatum, as an herbal medicine.

The name thoroughwort also comes from Eupatorium perfoliatum, and refers to the perfoliate leaves, in which the stem appears to pierce the leaf (i.e. go through, note that in older usage "thorough" was not distinguished from "through", compare for example the word thoroughfare).

Boneset, although poisonous to humans and grazing livestock, has been used in folk medicine,[10] for instance to excrete excess uric acid which causes gout.