In older references this plant is Eupatorium rugosum, but the genus Eupatorium has been divided into several more manageable genera. These plants were growing at the edge of St. Michael’s Cemetery on the South Side Slopes; White Snakeroot often forms dense stands right at the border between field and forest.
Here is what we wrote about White Snakeroot twelve years ago:
One of our most decorative late-summer and autumn flowers, White Snakeroot lights up the edge of the woods and can form a perfect ornamental border around a field. Its beauty comes at a price: it’s poisonous to cattle, and the poison can be transmitted through their milk. “Milk sickness” killed Abraham Lincoln’s mother. But if you don’t have cattle, there’s no reason not to enjoy this beautiful wild native.
As a member of the Composite family, this species is especially interesting for the way the individual little five-parted flowers are easily distinguishable in the heads. It’s a good plant for demonstrating the construction of a Composite flower to children.
Flowers: Heads discoid (that is, with no ray flowers), in irregular flattish corymbs; flowers pure white, with protruding stamens, also white.
Leaves. Opposite; oval, pointed, toothed, finely rough; underside with many prominent ribs; lower leaves flattish at base or almost cordate; on petioles about 1/3 the length of the leaves.
Stem: Smooth, flexible; much branched from leaf axils; averaging about 4 feet, but quite variable and can be much taller.