Flowers of the genus Eupatorium brighten late-summer roadsides and almost define the season in Pittsburgh. They are members of the Composite family (Compositae or Asteraceae), which means that, as with daisies or dandelions, each apparent flower is really a cluster of tiny flowers. Collectively members of the genus are all known as “thoroughworts.” Here are three of the most common species.
Snakeroot (Eupatorium rugosum) lives at the edge of the woods in large colonies, giving whole forests a broad white margin. A close look reveals the individual flowers that make up each head.
Joe-Pye-weed (Eupatorium fistulosum) is one of our most spectacular late-summer flowers. It can easily grow to eight feet high, and its faded mauve color is unique. The name, legend has it, refers to an Indian known as Joe Pye who used the plant to cure various ailments.
Thoroughwort or boneset (Eupatorium perfoliatum) lives in wet areas, as here at the edge of a marshy pond. Note how the opposite leaves completely surround the stem.