Most exotic plant species have only minor impacts on natural ecosystems. A small group of exotic plants, however, can be extremely disruptive. They may damage historic and archeological resources, interfere with natural processes, and threaten the survival of naturally evolved plant communities and individual native species. The National Park Service has as a goal the maintenance and restoration of not only individual species but all the components and processes of naturally evolving ecosystems. Therefore, controlling exotic species that have substantial impacts on park resources is a high priority.
Low priority is given to species that cause little damage or are virtually impossible to control.
Exotic plants are especially common in areas where construction, road building, or other human activity disturbs the soil. They often have a competitive edge over indigenous plants when they invade an altered site. Therefore, most of the exotic plants at Craters of the Moon are concentrated along the highway, and the dirt road and streams in the northern part of the monument. Others, like cheatgrass and field pennycress, are so widespread that control efforts would have little success. Common mullein is one of the most conspicuous exotic plants at Craters of the Moon.