Sweet joe-pye weed
Family: Asteraceae, aster family
Genus, species: Eupatorium purpureum
Leaves are in whorls of 4 or 5, elliptical, lance-shaped. Leaf edges are coarsely toothed.
Flowers are small, arranged in clusters at the tip of the stem. Petals are pale pinkish or purplish.
Eupatorium is named for Eupator, King of Pontus (northern Turkey), who was reputedly immune to poisons. The species name, purpureum, is from the Latin for reddish-purple.