Boneset, Eupatorium perfoliatum, is a common perennial that is native to the eastern United States and Canada, with a range from Nova Scotia to Florida. Other common names for boneset are feverwort, sweat plant, and thoroughwort. The Native American name for boneset translates into ague-weed (ague is the name for malarial fever ). The common name, boneset, comes from breakbone fever, an influenza-like illness causing severe bone pain that was treated with Eupatorium perfoliatum.

Historically, boneset was commonly included in medical herb gardens and used as a folk medicine for treatment of flus, fevers, colds and a variety of other maladies. Though some authorities claim the name boneset refers to a former use of the plant to aid the healing process for broken bones, others claim that the name is in reference to the plant's use as a diaphoretic in the treatment of an 18th century influenza called break bone fever. All parts of the plant are quite toxic and bitter. Also commonly called thoroughwort.

Boneset prefers a damp environment and is found in marshes and meadows, often at the edge of a wooded area, and notice invading home gardens. But, the bees and butterflies seem to enjoy it. Although boneset can reach a height of 5 ft (1.5 m), it is usually only 2–4 ft (0.6–1.2 m) tall. It has an erect, round, hairy stem that branches at the top. The leaves are large (4–8 in, or 10–20 cm, long), directly across from one another, and are joined at the stem. Lower leaves are large, and they become progressively smaller higher up the plant. They are spear shaped with toothed edges and pointy tips, have prominent veins, a rough topside, and a downy, dotted, sticky underside.

Genus name comes from the Greek name for these herbaceous and shrubby plants in honor of Mithridates VI Eupator, 132-63 B.C., King of Pontus, who reportedly discovered the medicinal uses for some Eupatorium species plants.

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