Ageratina altissima

Ageratina altissima, also known as white snakeroot,[2] richweed,[2] or white sanicle,[3] 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.

Plants are upright or sometimes ascending, growing to 1.5 metres (4.9 ft) tall, producing single or multi-stemmed clumps in mid to late summer and fall. The flowers are a clean white color and after blooming, small seeds with fluffy white tails are released to blow in the wind.

They are found in woods and brush thickets where they bloom mid to late summer or fall. The species is adaptive to different growing conditions; it is found in woods and brush thickets and also in shady areas with open bare ground, and can be weedy in shady landscapes and hedgerows. There are two different varieties: Ageratina altissima var. altissima and Ageratina altissima var. roanensis (Appalachian white snakeroot); they differ in the length of the flower phyllaries and shape of the apices.[4][5]