white snakeroot (Ageratina altissima)

Ageratina altissima, also known as white snakeroot, richweed, white sanicle, or tall boneset, is a poisonous perennial herb in the family Asteraceae, native to eastern and central North America. An older binomial name for this species is Eupatorium rugosum, but the genus Eupatorium has undergone taxonomic revision by botanists, and a number of the species that were once included in it have been moved to other genera.