Eupatorium perfoliatum

Eupatorium perfoliatum, known as common boneset or just boneset, is a North American perennial plant in the family Asteraceae. It is a common native to the Eastern United States and Canada, widespread from Nova Scotia to Florida, west as far as Texas, Nebraska, the Dakotas, and Manitoba. It is also called agueweed, feverwort, or sweating-plant. In herbal medicine, the plant is a diaphoretic, or an agent to cause sweating. It was introduced to American colonists by natives who used the plant for breaking fevers by means of heavy sweating, and commonly used to treat fever by the African-American population of the southern United States. The name "boneset" comes from the use of the plant to treat dengue fever, which is also called "break-bone fever." It is nearly always found in low, wet areas....read more on Wikipedia.