There’s a New Invasive in Town

By: Ben Johnston, Kickapoo Valley Reserve

In late November 2016, I met with Julie Borodin in Crawford County to learn about her experience with a relatively new invasive plant to Wisconsin, Burnet Saxifrage (Pimpinella saxifraga). Julie showed me the plants encroaching on her land. At first glance, the plants looked innocent enough, but as we walked along the town road we followed Burnet Saxifrage along the ditch and into the adjacent agriculture land. Plants were found on both sides of the road. “It is quite obvious,” she tells me, “it is moving with the mowers, as well as washing down slope with each rain event.” Julie has also spotted it on nearby county highways. It seems once you get a handle on which invasive plants to watch out for, another moves into the neighborhood.

Neither a member of the saxifrage family, nor related to the burnets of the rose family, Burnet Saxifrage is a member of the carrot family and perennial – living for many years. A common characteristic of the carrot family is a stem that ends in a cluster of flowers; and like several others in this family, this one is also white. The plant flowers as early as June, and can bloom as late as fall.

Cluster of white flowers (left) and plant structure (right) of Burnet Saxifrage. Photos by K. Chayka and Peter M. Dziuk taken at Elm Creek Park Preserve, Hennepin County, MN (www.minnesotaflowers.info)

The plant height and flowers are very similar to Queen Anne’s Lace; it’s about three feet tall with clusters of white flowers. But upon closer inspection, the seedlings and lower leaves of the plant resemble Wild Parsnip, another common invasive species; however, Burnet Saxifrage has more deeply toothed margins on shorter and rounder leaves. They are definitely different, but with a quick glance one might be mistaken. The mid- and upper leaves are different yet, becoming smaller and more deeply lobed as they make their way up the stem. The stems are slightly ribbed and covered in very short hairs. Overall, the plant looked so much like Queen Anne’s Lace that I dread looking more closely at any Queen Anne’s Lace patch, since it is quite possible, it is intermixed with Burnet Saxifrage.

The lower leaves (left) and upper leaves (right) of Burnet Saxifrage. Photos taken by Ben Johnston, Kickapoo Valley Reserve

Since it’s a relatively new invader, questions arise as to what kind or how much of an impact this plant will have. Will it spread rapidly, but peacefully intermingle with the others; or will it replace and dominate the native vegetation? According to the Minnesota Wild Flowers website, reports from Beltrami County, Minnesota indicate Burnet Saxifrage forms a mat preventing other plants from growing. Furthermore, Angela Isackson at Three Rivers Park in Minnesota has noticed, “We have an infestation spreading into old fields, forming a dense carpet, and out-competing Brome grass and Oxeye Daisy. It’s not a good sign”.  Together these observations indicate that Burnet Saxifrage may indeed by a threat to the native vegetation.

Burnet Saxifrage infestation. Photo taken by Peter M. Dziuk at Elm Creek Park Preserve, Hennepin County, MN (www.minnesotaflowers.info)

What if you find this new invasive on your property? Burnet Saxifrage reproduces by seed only, so preventing seed production is the first goal.  If seed heads develop, collect and bag the seed. Repetitive mowing can prevent flowering and deplete nutrient storage in the roots. However, if a flower head is cut the plant will likely re-flower; pulling needs to get the entire tap root.  Herbicide applications will kill plants, but can come with additional costs if used incorrectly.  Be sure to read the herbicide label to ensure correct use and efficiency. Regardless of the control method chosen, all methods need to be prompt and thorough.

Sure enough, after leaving the property, I found some plants alongside Crawford County Highway C just west (less than 1 mile) of Soldiers Grove. Some of these plants were still in flower and green (remember this was late November); other plants had gone to seed. According to the University of Wisconsin – Herbarium records, Burnet Saxifrage is located in nine counties of Wisconsin, including Crawford County, found in 2006.

By no means do I intend to create despair or hopelessness among landowners, but rather I encourage all to learn what is “supposed” to grow on your land, and be on the lookout for plants that do not belong. The best approach for invasive species control is early detection and rapid response.

Be aware that there are other invasive plants with white clusters of flowers that are spreading throughout Wisconsin: Japanese Hedge Parsley, Giant Hogweed, Wild Chervil, and Poison Hemlock.  Some members of the carrot family you want on your property include, Golden Alexanders, Water Hemlock, cow parsnip, and Sweet cicelies; these are among the friendly native types.

For more information and resources for invasive plants, consider visiting Invasive Plants of Wisconsin (IPAW), Wisconsin Department of Natural Resources, or University of Wisconsin-Extension Weed Science websites.

Contact Ben Johnston at ben.johnston@wisconsin.gov