In September, White Snakeroot (Ageratina altissima) is commonly seen in flower in ravines, floodplains, openings in forests, river banks and along trails. I even find it every year growing in my garden as a weed.
The plant has so many tiny white flowers that Newcomb’s Wildflower Guide classifies the flower type as “Flower Parts Indistinguishable”.
The toothed leaves are opposite to each other.
A toxic substance in this plant can cause “trembles,” a fatal disease of cattle which have browsed on it and which is transmittable to humans by their milk.
During the early 19th century, when large numbers of European Americans from the East, who were unfamiliar with snakeroot, began settling in the plant’s habitat of the Midwest, many thousands were killed by milk sickness. Notably, milk sickness was possibly the cause of death in 1818 of the mother of Abraham Lincoln.
It took quite a few decades until people connected the cause of these deaths with White Snakeroot. In the 1830’s a member of the Shawnee tribe warned a doctor, Dr. Anna Hobbs Bixby, about the effects of this plant. Dr. Hobbs is credited with the discovery of the cause of milk sickness.
On a separate note, I have always found this plant very difficult to photograph because of the tiny individual flowers and the bright white colour.
It is never well in focus.
One day I took a tripod and really worked at getting an in-focus image. Here it is.
It’s particularly interesting to me to read this article after you have pointed out this plant on your nature walks, where we saw quite a lot of it.