By Orien Anderson
Are there strangers in your woods? Chances are your woods have been invaded by multiflora rose, bush honeysuckle, autumn olive, buckthorn, garlic mustard or some other exotic invasive species. These plants are competing with native plants and are changing the makeup and diversity of our woodlands. For example, bush honeysuckle is shade tolerant and chemically prevents growth under its leaves. It is easily recognized in the fall since its leaves stay green after other plants have dropped their leaves. If you have honeysuckle, you will notice there is a biological desert under the plant. Removing this plant will result in regrowth of native species. A great source to identify these invasive plants is: http://www.invasive.org/illinois/SpeciesofConcern.html
Besides competing with native species, these exotics have a detrimental effect on wildlife and the forest ecosystem. Most of these invasives are prolific seed/berry producers and their seeds/berries are “junk food” for wildlife since they lack the high energy fats of native plants. Native plants are deeper rooted and will hold forest soils and prevent erosion. Some invasives such as buckthorn produce a chemical that leaches into amphibian ponds and kills the embryos. Garlic mustard will blanket the forest floor and compete with spring wildflowers and inhibits oak regeneration. When its seed pods dry, they propel their seeds as you walk along.
Control of invasives can be successful using a variety of methods. One is to plant native species such as dogwood and hazelnut to compete. Using a ground fire helps eliminate unwanted plants. These methods work if the infestation is light. For most situations, mechanical and chemical control methods will be needed. Plants, such as honeysuckle, are shallow rooted and the small plants can be easily pulled. Larger plants will need to cut off or girdled with a chainsaw. The stump surface or girdled cut can be treated with a 50/50 solution of glyphosate concentrate and water. This mix can only be used above freezing because glyphosate is water soluble and water freezes. Otherwise you can switch to Garlon and basal oil when it drops below freezing. It is important to treat the cut soon after cutting since the stump will seal over and prevent translocation of the chemical.
Plants can also be leaf sprayed with a 1.5% glyphosate solution. Care must be taken to minimize spray drift to avoid damaging non target plants. Leaf spraying bush honeysuckle in the early fall when these plants are green and other plants have had leaf drop minimizes drift concern. Be sure to read all herbicide labels thoroughly.
If you fail to recognize and treat these “strangers”, your woods will soon be unrecognizable and inaccessible to you. Imagine if you let an invasion of water hemp take hold in your crop fields for a few years. Control of these invasives is vital in order to keep your native woodlands.