Western Ironweed - Vernonia noveboracensis

Other names: Baldwin's ironweed
Family: Aster (Asteraceae)
Habitat: moist thickets and stream edges
Height: 3-7 feet
Flowers: purple flower heads 1/2 to 3/4 inch across, in clusters 3-5 inches across
Flowering time: August to October
Origin: native

Sources

USDA
Conn. Botanical Society - https://www.ct-botanical-society.org/galleries/vernonianove.html
Photos: Courtesy S. Peregrine Johnson.

Western Ironweed - Vernonia noveboracensis