Distinguishing Eupatorium plants can be confusing, as many plants formerly included in the genus have been moved to other genera. For instance, Ageratina (snakeroot), a genus that now contains more than 300 species, was formerly classified as Eupatorium. Joe Pye weeds, previously known as types of Eupatorium, are now classified as Eutrochium, a related genus containing about 42 species. Today, most plants classified as types of Eupatorium are commonly known as bonesets or thoroughworts– although you may still find some labeled as Joe Pye weed. Read on to learn more about distinguishing Eupatorium plants. Differences Between Eupatorium Plants Common boneset and thoroughwort (Eupatorium spp.) are wetland plants native to the eastern half of Canada and the United States, growing as far west as Manitoba and Texas. Most species of bonesets and thoroughworts tolerate cold as far north as USDA plant hardiness zone 3. The primary distinguishing characteristic for boneset and thoroughwort is the way the fuzzy, erect, cane-like stems seem to perforate, or clasp, the large leaves which may be 4 to 8 inches (10-20 cm.) long. This unusual leaf attachment makes it easy to tell the difference between Eupatorium and other types of flowering plants. The leaves are lance shaped with finely toothed edges and prominent veins. Boneset and thoroughwort plants bloom from midsummer through fall producing dense, flat-topped or dome-shaped clusters of 7 to 11 florets. The tiny, star shaped florets may be dull white, lavender, or pale purple. Depending on the species, bonesets and thoroughworts can reach heights of 2 to 5 feet (61 cm. to 1.5 m.). All species of Eupatorium provide important food for native bees and certain types of butterflies. They are often grown as ornamental plants. Although Eupatorium has been used medicinally, it should be used with great care, as the plant is poisonous to humans, horses, and other livestock that graze the plants.
