White snakeroot sounds like something that one of the three witches in Shakespeare’s “Macbeth” might have added to their pot of brew, along with
“Eye of newt, and toe of frog,
Wool of bat, and tongue of dog,
Adder's fork, and blind-worm's sting,
Lizard's leg, and owlet's wing …”
And white snakeroot (Ageratina altissima) IS poisonous, though I doubt that anyone would think to eat it; it’s just a pretty flowering plant. That is, unless you confuse it for late boneset (Eupatorium serotinum), another native perennial.
It was several years ago (2017) that I noticed a new flowering “weed” in my garden in early fall. It was tall, with notched, opposite leaves and branching heads of tiny white flowers. It was also trying to take over. So, my first question was, “Is this a native plant or something that was introduced?” My money was on the latter possibility, because once I noticed it on my own property I started seeing it everywhere — along almost every roadway, scattered in gardens in West Chester Borough, and even growing up out of a crack in the pavement. Surely this must be an invasion of an aggressive, non-native species!
I took a close look at the flowers. They reminded me of something really familiar but I couldn’t place them, so I contacted the Penn State Agricultural Extension Service in West Chester, attaching a photo and asking if they could tell me what it was. Within a few hours, I received a reply from one of the volunteer Master Gardeners.
The email read, “I believe you are looking at a boneset plant. I too had some show up in my yard and had to work on identifying it.” The email included a link to an article/description.
I eagerly followed the link provided, only to discover that we did not have a match. I took a close-up photo of the leaves to send in, showing that those on my plant had long petioles attaching them to the stems. No way this could be boneset, which has leaves that grasp the stem (sessile).
The second photo did the trick. The master gardener wrote back. “I contacted one of our members who’s an expert at identification, and she said she believes it is snakeroot. I will send information and see what you think.” I accessed the embedded link and breathed a sigh of accomplishment. Finally, I had a positive I.D. — white snakeroot it was.
The URL linked me to the website of the Brooklyn Botanical Garden and an article by Saara Nafici. I had to laugh when I read the first few lines: “Fall-blooming white snakeroot is that nondescript weed that has been inconspicuously growing in shady spots all spring and summer. You barely notice the one- to four-foot-tall plant with toothy, dark green leaves until suddenly — poof! It’s everywhere you turn, all abloom with fluffy white flowers.” That pretty much summed it up.
In addition to being pretty, white snakeroot is eagerly sought by bees, moths, and flies “furiously foraging before the weather turns cold and food becomes scarce.” Unfortunately, as Nafici also notes, this plant “played an unfortunate role in American history. In the early 19th century, European settlers, unfamiliar with the plant, allowed cows . . . to feed on it. A toxin in the plant called tremetol tainted the cow’s milk, causing sickness and death to those who drank it. ‘Milk sickness’ claimed the lives of thousands of people, including, it is thought, Abraham Lincoln’s mother.” The story improves. Anna Pierce Hobbs Bixby, a frontier doctor, learned the cause of the sickness from a Shawnee medicine woman, and helped control the disease locally by instructing settlers to remove white snakeroot from their fields. It would be years, though, before the medical profession accepted her findings.
You can read Nafici’s article at: https://www.bbg.org/news/weed_of_the_month_white_snakeroot
Pam Baxter is an avid organic vegetable gardener who lives in Kimberton. Direct e-mail to email@example.com, or send mail to P.O. Box 80, Kimberton, PA 19442. Join the conversation at "Chester County Roots," a Facebook page for gardeners in the Delaware Valley. Go to Facebook, search for Chester County Roots, and "like" the page. To receive notice of updates, click or hover on "Liked" to set your preferences.