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Wild Side Column: Battling buckthorn

UWRF students cutting buckthorn and treating the stumps at the Kinnickinnic River Land Trust Kelly Creek Preserve. Dan Wilcox photo.

Now is the time to do battle with buckthorn. Buckthorn is an invasive shrub that was brought to North America from Europe as an ornamental hedge plant. Buckthorn is rapidly invading our area.

Buckthorn is easy to identify. It has oval-shaped glossy green leaves with finely serrated edges and a pointed tip. Their leaves stay on long into the fall after most other trees and shrubs have lost their leaves. The twigs often end in small sharp thorns. The bark on larger buckthorn shrubs is rough, dark brown with corky projections. The shrubs are tough and "grabby."

Buckthorn is a major problem in many ways. The female plants produce numerous small dark berries with seeds that are widely distributed by birds. It forms dense, nearly impenetrable thickets up to 15 feet high that out-compete native plants for nutrients, light and water. It leafs out early and holds leaves late into the fall, contributing to erosion by shading out plants that grow on the forest floor. Buckthorn thickets degrade wildlife habitat. Even deer avoid buckthorn thickets. Buckthorn in North America lacks natural controls like insects or diseases that would reduce its abundance.

Several years ago, much of the Foster Cemetery area uphill from the wastewater treatment plant in River Falls was overrun with buckthorn, crowding out the native oak savanna vegetation. The Prairie Enthusiasts volunteers put in a lot of time cutting and burning buckthorn and applying herbicide. TPE brought in a "tree shark" machine to grind up the densest buckthorn patches and then applied herbicide to the buckthorn that grew back.

Last Saturday TPE volunteers used backpack sprayers to apply herbicide to the buckthorn sprouts on the Alexander Oak Savanna across Highway 65 from the River Falls Town Hall. It was heartening to see the native prairie grasses and forbs thriving in the areas that have been mostly cleared of buckthorn.

Last Friday, Dr. Eric Sanden and 13 Prairie Restoration and Fire Ecology students from UW-River Falls came out to the Kinnickinnic River Land Trust Kelly Creek Preserve northeast of River Falls. They learned to identify buckthorn, cut it with loppers and applied herbicide to the cut stumps. They were enthusiastic and got quite a bit done in the short time they had on site.

It's not easy to control buckthorn but it is worthwhile to protect woods and oak savanna areas. Small buckthorn seedlings less than 3/8 inch in diameter can be pulled by hand if the soil is wet. Special lever tools are available to pull larger buckthorn plants.

The best time to control buckthorn is in late summer and fall. Herbicide applied at this time of year is drawn down into the roots, killing the plant. Larger buckthorn shrubs can be killed by cutting with a large brush lopper or chainsaw and then by applying herbicide to the cut stump. Herbicide containing the chemical triclopyr (Garlon®) or glyphosate (Roundup®) works well. 20 percent Garlon mixed with bark oil and a marking dye works well. Apply the herbicide sparingly to the cut stump to avoid killing other nearby plants. Standing buckthorn can be killed by foliar application of 2 percent (4 ounces per gallon) Garlon using a backpack sprayer. The herbicide can be purchased at farm supply stores. Follow the directions carefully for mixing and applying herbicides.

We have been working hard to control buckthorn on our place but it appears that we will have to keep at it for years. We don't want to see our woods turn into impenetrable thickets of nasty buckthorn.

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