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Why Buckthorn Threatens Minnesota Plant & Animal Ecosystems

In a recent blog post we discussed Minnesota invasive plant species and the general threats they pose to our environment. In this article we’d like to focus on one of the biggest problem plants, the buckthorn. Not even a factor just a few decades ago, buckthorn control is at the top of the list in our plant management programs.

First, what exactly is buckthorn and how did we get it here in Minnesota?

Common Buckthorn

Not to be confused with sea buckthorn, common buckthorn (Rhamnus cathartica )is a plant species that isn’t even native to North America, let alone our state. It was first brought to this country in the 1800s from Europe for landscaping use. (It’s a native plant throughout Europe and western Asia.) Its use in the U.S. wasn’t widespread until the 1900s, when it became very popular for windbreaks and hedges.

Buckthorn is a deciduous tree (some classify it as a shrub, probably depending on its size). It can reach up to 20′ in height, and it spreads easily because it is a prolific seed producer. There are currently no natural insect predators in this country, and even deer who aren’t very picky about what they browse on will avoid it. However, birds with no other food sources eat its dark blue berries and in their droppings spread the seed far and wide. Because of this, as well as the fact it is incredibly hardy and does well despite lack of light or poor soil conditions, it has almost taken over some areas of forest and savannah.

Why is buckthorn such a threat?

As with other invasive plant species, buckthorn poses a threat to both local animal and native plant communities because it tends to crowd out other plants, especially those that local wildlife depend on for food and shelter. It competes – and wins – with native plants for space, water, and nutrients in the soil because it has no natural control forces. Left uncontrolled, it will dominate a local ecosystem.

Buckthorn berries are a poor source of food for birds, and those which eat the berries do so because their normal food sources have been crowded out. And because it takes over an area, that leaves the native insects, including bees and butterflies, without food. And as insects leave the area because of lack of food, the birds that normally eat those insects will move out as well. That leaves no food source for small animals that would eat birds. Entire insect, bird, or small animal species can disappear from an area.

Other problems with buckthorn:

  • Its berries have a laxative effect, and the resulting diarrhea can be fatal for the small birds and occasional mice that consume them.
  • Buckthorn, as it decomposes, alters the soil composition. It can raise the nitrogen levels in the soil, encouraging the growth of weeds and other invasives.
  • Buckthorn crowds out native species of ground cover plants. Soil instability and erosion result, and rainwater flows undeterred into nearby water sources such as lakes and rivers.

It’s not uncommon for our first step in native plant community restoration to be removal of existing buckthorn. But that’s not a once-and-done process, because with the spread of the seeds it keeps cropping up. Cutting and controlled burns to remove mature plants are our two most common methods. Some landscapers will use chemicals to control it, but those have their drawbacks as well. There is currently no known safe, biological enemy for buckthorn, so we need to repeat our cut-and-burn process for a number of years until it’s completely removed from the area and there are no more plants to produce seed and keep the growth cycle going. It’s just part of our integrated plant management projects.

Buckthorn can be found throughout the state unfortunately, which means we’ve got our work cut out for us. If your property has buckthorn present, we can help. Give us a call at 1-800-837-5986.

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