Now called Ageratina altissima 'Chocolate'.

White Snakeroot.

This cultivar has small white fluffy flowers arranged in rounded, broccoli-sized heads 15cm across atop shiny purple stems typically rising 100 to 150cm tall. Sharp-toothed, lance-shaped to elliptic-oblong leaves (10 to 18cm are chocolate-tinted, thus giving rise to the cultivar name. The species is native to woodlands in the Eastern United States. 

Height 100 to 160cm Spread 80 to 100cm.

2 litre pot