The Dreaded Glossy Buckthorn

By Coggin Heeringa, Program Director/Naturalist, Crossroads at Big Creek

At this time most winters, Crossroads at Big Creek is cloaked with mounds of snow. This year, we still have numerous mounds, but they are not snow. They are the trunks and branches of Rhamnus frangula, the dreaded glossy buckthorn, an invasive species.

The lag in winter snow, which has truncated our Ski for Free season, has greatly expanded the time Crossroads staff, volunteers and restoration contractors have been able to work on buckthorn removal along Big Creek.

So, what’s the big deal about buckthorn, and why are we putting so much effort into the removal of this invasive species?

In his book “Nature’s Best Hope,” Douglas Tallamy wrote: “Invasive plants are defined as non-native species that displace native plant communities…Native plants, aggressive or otherwise, have been duking it out with one another, competing for space, light, water and nutrients, for millions of years. Over the eons, native species have evolved ways to cope with one another, and the results of the interactions define the highly diverse species of most native plant communities.

“Invasive plants,” Tallamy continued, “in contrast, have arrived in a community within the last several hundred years, which is a blink of an evolutionary eye. They also have arrived without their suite of natural enemies—insects, mammals, and diseases that keep them in check in their homeland….”

And that is true of the buckthorn at Crossroads and throughout Door County. These trees were intentionally brought to the United States as landscaping plants.

Buckthorn thrives because it has a long growing season. It leafs out very early in spring and also retains its leaves long into fall. This means that buckthorn trees create shade and out-compete native plants for light, water, and nutrients. There is evidence that buckthorn is mildly allelopathic, which means the roots seem to produce chemical compounds that inhibit the growth of other vegetation. Consequently, buckthorns create dense thickets. 

Unfortunately, these dense buckthorn thickets have been dominating most of the 25 acres along the stream corridor and associated wetlands of Big Creek.

Last year, Landscapes of Place, LLC developed an Ecological Restoration Plan for Crossroads at Big Creek. The first guiding principle is to “begin at the Creek and work outward. Big Creek and its associated habitats are the most ecologically significant for wildlife using the preserve, and also serve at the primary inspiration for community members’ engagement at the preserve.”

Because buckthorns do not contribute to the health of the creek environment, we are removing them.

“Restoration in progress” sometimes looks messy or harsh – hence the mounds of branches. But removing buckthorn, along with other invasives like honeysuckle and reed canary grass, paves the way for us to nurture the native plants – both the ones we introduce and ones that regenerate on their own – that will begin to heal this challenged habitat.

We are calling our restoration volunteers “Habitat Healers,” and throughout the coming months, we will be inviting volunteers to join the Healers to remove invasives and in-plant natives to provide an early landscape character that will result in the healthy, diverse and largely self-sustaining ecological community we envision. This is an evolution you’ll want to watch. So whether you’re on skis, snowshoes or foot, next time you’re at Crossroads, be sure to include the North Bridge area in your foray and pay special attention to the mounds of buckthorn that shows our progress.

Crossroads at Big Creek Learning Center and Nature Preserve is located at 2041 Michigan Street, Sturgeon Bay, Wisconsin. Crossroads is a 501(c)3 organization committed to offering education, conducting research and providing outdoor experiences to inspire environmental stewardship in learners of all ages. We welcome your support! Become a member of Crossroads by mailing your support to P.O. Box 608, Sturgeon Bay, WI 54235, or donate online at www.crossroadsatbigcreek.org