Invasive plant species are plants that are not native to an ecosystem and potentially cause economic or environmental damage to the area. Many plants have been introduced into the north central United States without much impact, but a few species, such as garlic mustard, buckthorn, multiflora rose, and bush honeysuckle, have become very problematic and are impacting woodlands severely. The extent of these species' invasion needs to be known before a plan of action can be developed.