FROM THE GROUND UP: Garden ‘weed’ turns out to be native plant and might be growing in a garden near you

White snakeroot — blooming now on a roadside near you.
White snakeroot — blooming now on a roadside near you. PHOTO BY PAMELA BAXTER

Last week I noticed a new flowering “weed” in my garden. It’s tall, with notched, opposite leaves and branching heads of tiny white flowers. It’s 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 parking lot at the Kimberton Inn. Surely this must be an invasion of an aggressive, non-native species!

I took a close look at the flowers; they reminded of something really familiar but I couldn’t place them. Then I happened to walk past some purple ageratum. Apart from the color, the flowers looked the same. “Aha!” I thought. “This must be a cousin.” The problem was, no matter how hard I tried, I just couldn’t make the description of this new plant fit that of ageratums. Ageratums as a group had much more sedate characteristics than this rampant plant.

Finally, 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 couple of 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. Boneset can get quite tall and it is a perennial so if you don’t want it you will have to pull it out and watch for any seeds that may germinate that it leaves behind.” The email included a link to an article/description.

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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 show that the ones on “my” plant had long petioles attaching them to the stems. No way could this be boneset, with leaves that grasp the stem so that it looks like the stem is growing through the leaves.

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 snake root. 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; botanical name Ageratina altissima.

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.

Surprisingly, white snakeroot turns out to be a native plant, eagerly sought by bees, moths, and flies “furiously foraging before the weather turns cold and food becomes scarce.” A visit to the Missouri Botanical Garden website (http://bit.ly/2xbxsIA) revealed that the plant can grow to five feet tall with a spread of up to four feet. This is a big plant! I laughed again when I read, “This is a somewhat weedy perennial that can spread aggressively by rhizomes and self-seeding.” Rather an understatement!

White snakeroot is in the aster family. I find it interesting that both this plant and the native purple aster bloom prolifically at this time of year, providing a late-season nectar source for pollinator insects. It’s also interesting that White Snakeroot has another botanical name: Eupatorium rugosum.

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 pamelacbaxter@gmail.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.