Ageratina altissima (Eupatorium rugosum)
This is a poisonous plant that is native to North America. The plants grow to about 3-4 ft.; the very small white flowers are born at the top of the plant in loose clusters that might remind you of boneset or a white ageratum. The leaves are opposite, ovate to cordate, and toothed, with long petioles.
White snakeroot is responsible for a kind of human poisoning called “milk sickness”. People who drink the milk or eat the meat of cattle that have consumed a lot of snakeroot will suffer severely and may even die as a result of the toxin (tremetol). Thousands of early settlers who were unfamiliar with this plant died as a result of milk poisoning. The plants are also poisonous to other animals, including horses and sheep. Surprisingly, the plant gets its name from the fact that it was once mistakenly believed to be a good remedy for snakebites.
Snakeroot is a perennial herb that likes to grow in moist, shady places. I found this colony of plants growing at the wood’s edge, in partial shade, on the floodplain of Tom’s Creek in Blacksburg, Virginia.
Bloom time is late summer and fall. Other common names include tall boneset and white sanicle.