Buckthorn invasion choking out our native plants


You can see many different tree and woody shrub species when you’re out exploring the forests along the Mississippi or elsewhere in Minnesota. One shrub or small tree you might come across goes by the name European buckthorn. Since its introduction in the mid-1800s this invasive species has become a real headache for those who want to restore woodlands.

An invasive species is not only something that is not native to an area, but something that also causes harm either economically or environmentally (usually both). You may have heard about invasive zebra mussels which are spreading through Minnesota lakes and waterways, or invasive emerald ash borer which is decimating ash trees as it steadily spreads west across the U.S. Originally brought to the U.S. as an ornamental shrub, today European buckthorn creates dense thickets in the understory of forests across most of the country.

Invasive species tend to be so damaging because they have no natural predators or natural controls that can regulate its growth. Deer and other animals that browse much of the forest understory avoid consuming buckthorn, giving it a leg up over native species. Buckthorn leaves also stay on the plants longer than the leaves of native woody species, allowing buckthorn to gather energy from the sun to extend their root systems while everything else in the forest has gone dormant. The large populations of buckthorn that result outcompete other understory plants that help retain soil, resulting in bare ground that will wash away more easily in rain and wind.

Here are a couple ways to identify buckthorn:

  • The leaves: Buckthorn leaves are usually glossy so they feel smooth when you hold them, and are lighter on the undersides than on top. If you look closely at the veins you will see that they curve slightly and that when they come together in the middle they are slightly off-centered.
  • The bark and stems: The bark is usually gray and the stems are tipped with a pointy thorn.
  • The fruit: Small purple/black fruits appear in clusters on mature plants in the fall.

In the fall buckthorn is particularly easy to identify as its leaves will remain a rich green as the leaves on the trees around it change to yellows, oranges and reds.

Fall is the best time to remove buckthorn. Limiting the spread of buckthorn and removing it from forests or prairie edges is important for preserving the diversity of Minnesota’s ecosystems. If you find buckthorn in your backyard you can pull seedlings by hand or remove larger diameter buckthorn with a ‘root talon’ or by digging it out with a shovel. Very large buckthorn should be cut down at the base of the plant, and the stump should either be treated with an herbicide or covered with a can or black plastic for a year to prevent re-sprouts. Visit the MN DNR website to learn about buckthorn removal, dnr.state.mn.us/invasives/terrestrialplants/woody/buckthorn/control.html.

Come out to the Carl Kroening Interpretive Center at North Mississippi Regional Park and have a naturalist show you exactly what buckthorn looks like and how it threatens the health of our park. Join us on weekends for free activities! Saturdays from 11 a.m.-3 p.m. stop by our naturalist’s nature table where we’ll have simple activities and a craft. Stay for five minutes or all day!  Sundays from 12:30-3:30 p.m. drop in for Family Fun-day, grab prepared activities that are fun for the whole family and head out into the park for some quality family time in nature.

Here is the schedule of themed weekends in October.

October 1/2 – Insects Above and Below: find out how insects are contributing to the world all around us.  October 8/9 – Life on the River: learn about riparian habitats and the water of the mighty Mississippi.  October 15/16 – Autumn Prairie: collect and help disperse seeds and see how the prairie winds down as the temperatures drop.  October 22/23 – Paws and Claws: search out tracks and discover who left them.  October 29/30 – Fall Harvest Nature Art: let fall foods and colors inspire your creativity and the artist within.