Invasive plants are a major threat to Wisconsin’s forests, highlighted in the forest health chapter of Wisconsin’s Forest Action Plan. Invasive plants limit tree regeneration, reduce plant diversity and increase management costs. Recent Forest Inventory and Analysis data from the USDA Forest Service found that more than half of forest sites surveyed in Wisconsin had two or more invasive plant species. Forest landowners should learn to recognize common invasive plants like buckthorns, honeysuckles and garlic mustard. Mobile applications are a handy tool for landowners to learn to identify the plant species in their woods (e.g., PlantNet, iNaturalist) and report invasives (e.g., EDDMapS). For information about the regulated invasive plants in Wisconsin visit the Wisconsin Department of Natural Resources’ (DNR) Terrestrial Invasive Species page.
Controlling invasive plants is easiest when the population is small and there are fewer seeds in the soil. Walking your forest stand regularly will help you monitor for new plants that may be invasive or undesirable. On heavily infested sites, the goal of invasive plant management may be to reduce populations long enough to establish regeneration of desirable plants. This may be accomplished with a combination of mechanical removal and herbicides. For example, before thinning or regenerating a hardwood stand, a forester may work with a contractor to forestry mow the site and then treat the regrowth with herbicide one or more times before the timber harvest occurs.
Removing invasive plants can be difficult and time consuming. The DNR provides limited cost share money for Cooperative Weed Management Areas and private landowners to control invasive plants. EQIP funding from the USDA Natural Resources Conservation Service is another source of invasive removal funding. Additional grants options are listed here. Detailed control information for many Wisconsin invasive plants can be found on the Midwest Invasive Plant Network website.