White snakeroot, Ageratina altissima
 
Many clusters of showy white flowers bloom from late summer until frost. Plants typically reach 60-120 cm in height.
 
Growing Conditions:
This plant is well-suited for woodland edges and part shade. It prefers disturbed, somewhat moist soils but can tolerate a wide variety of conditions. It is a very hardy plant. Rabbits and deer don't eat it because of its bitter taste. Be aware that it is toxic to dogs. 
 
Ecology:
White snakeroot attracts many sizes of bees, even in the shade, and is a host plant for different moths.