by DALE NEWCOMB, Winona County Master Gardener volunteer
If you are traveling on many of the country roads in Winona County in late October or through November near wooded areas you probably will notice certain plants that still have dark green leaves. They stand out because most other plants have lost their leaves. If you look even closer you will notice small, black, round berries on many of the branches. These plants are common or European buckthorn. They are an invasive species that were brought here from Europe in the late 1800s, and they were planted to be used as hedges. The buckthorn didn’t stay in the hedges for long. They spread into nearby forests, parks and roadsides. Today the plants can be found in almost every Minnesota county.
Now to get to the meat of the problem. The buckthorn plants leaf out early in the spring and the leaves stay on later in the fall. They also grow as tall as small trees. This creates a dense shade which helps it outcompete many other native plants. They also don’t have any natural controls like insects or diseases to kill them. Once the plants get established, they form a thick mass of brush that can’t be penetrated by man or beast — a little exaggeration there. Being an avid deer hunter, I have found areas where I used to be able to walk through that I can no longer hunt successfully because of the mass spread of the plants. Some other problems they cause are erosion because they shade out other plants that grow on the forest floor and they have been known to be hosts to other pests like the crown rust fungus and soybean aphids.
So now that we know what the buckthorn looks like and the problems they cause, what can be done to control the spread? All control methods are very manual labor intensive. The first plants that you want to remove are the ones that have the berries on them because that is the main method of how the plants spread. The berries are eaten by birds or other wildlife and the seeds are carried to other locations in the area. New plants then grow where no buckthorn plants had been growing. Also the berries that fall to the ground contain seeds which develop into more new plants.
These bigger plants should be cut off at the soil surface and the stump should be treated with a herbicide containing Triclopyr such as Ortho Brush-B Gon, Bonide Kleenup or Garlon 3A or 4. This treatment should be done within two hours after cutting and can be done with a paint brush. The cutting should be done preferably on days when there isn’t rain expected for a couple days allowing the herbicide to soak into the stump. Once all of the berry-bearing plants have been removed, then the remaining plants should be removed, too. You would use the same method on the bigger plants as previously explained. The small plants and seedlings can be removed by pulling them out by hand and they won’t resprout. If there are too many seedlings to be pulled by hand, spray them with a Triclopyr herbicide. Larger plants that are bigger than a half inch in diameter and up to 2 1/2 inches in diameter can be pulled out by using hand tools called a Weed Wrench or a Root Talon. These tools will dig under the roots of the plant so it does take some effort to use them. The Minnesota Deptartment of Natural Resources (DNR) will be able to give you information about where to find a source for these tools. You can contact the DNR at 888-MINN-DNR or www.mndnr.gov.
There isn’t any definite suggestion about how to dispose of the removed buckthorn. The Minnesota Deptartment of Agriculture (MDA) has classified buckthorn as restricted noxious weeds. One of their suggestions is to burn the plants, but in many cases that would not be a viable choice especially in an urban location. Another option would be to take the cut buckthorn to a compost site but some sites may not accept them. MDA recommends not moving the plant remains from the property where it had originally grown. The area where the buckthorn was removed from must be re-visited for several years to remove any new seedlings that have grown from the seeds left over from the old plants.
I have observed an area in the William O’Brien State park where the older buckthorn plants were removed and put in piles. The piles were burned over a period of a year. After the buckthorn was removed the native wild flowers in the area grew easily without the shade from the buckthorn inhibiting their growth. Joe Pye weed was one of the flowers that came back quickly. It was a beautiful alternative to the green tangled invasive buckthorn plants. That was about four years ago and the buckthorn was not removed in succeeding years so the native plants are being smothered out again from the buckthorn regrowth.
If you are interested in putting some other species of plants in place of the removed buckthorn there are several suggestions. High-bush cranberry, nannyberry, choke cherry, grey dogwood, pagoda dogwood and American hazelnut are good replacements. The dogwoods will require richer soil and are good targets for deer damage. The other plants will grow in a variety of soil types. If there is an extensive amount of soil disturbance from removing the smaller plants there are several different types of rye seeds that can be planted to help control any soil erosion that might occur. You should wait at least two years before replanting with other plant types.
This is a daunting task to try and eliminate the buckthorn plants completely, and I don’t believe that is possible. However, if the spread of the plant can be slowed to some extent by removing those plants that are easily accessible, then we may give our native plants a little help in growing back.
More information about the buckthorn removal project can be attained from the DNR or the local county Extension offices.