Nonnative Invasive Plants

Exotic plant species have been introduced into the Southern Appalachians since the beginning of European settlement of the region. Many of these introductions have posed no problems, remaining essentially within the boundaries of human cultivation. Some, however, have escaped and spread, displacing native vegetation, causing ecological disturbance and, in some cases, causing economic loss or impairing land use (SAMAB 1996e).

Most Invasive Plant Species in the Southern Appalachians

The Southern AppalachianMan and Biosphere formed the Southern Appalachian Native Plant and Invasive Species Initiative to increase understanding and awareness of invasive plants in the Southern Appalachians. As a part of this initiative, an Invasive Plants Assessment is being conducted to determine the extent and impact of invasive plants in the Southern Appalachians. One of the initial results of this assessment is to identify the most problematic invasive plants on public land of the region. SAMAB queried 41 state, Federal, and nongovernmental agencies about nonnative species. Although a total of 263 plant species were reported as invasive within the region, most agencies reported a particular set of "dirty dozen" species which posed their greatest ongoing and potential management headaches (Table:Frequently reported invasive plant species on public land in the Southern Appalachians).

Kudzu Pueraria montana	A fast-growing Asian vine that covers some 7 million acres of land (an area larger than Vermont) in the Southeastern United States. Prior to 1953 the plant was widely grown as livestock forage and as a means of controlling erosion. Park crews have largely contained the spread of kudzu in the Smoky Mountain National Park and they continue to monitor 116 sites and treat them as needed.
Japanese honeysuckle Lonicera japonica	A woody vine introduced for erosion control, wildlife cover, and as an ornamental. It forms ground-covering mats and dense infestations of tree-climbing vines in forest margins, rights of way, and other open spaces. Its persistent green leaves photosynthesize in winter, increasing its ability to dominate native plants.
Oriental bittersweet Celastrus orbiculatus	A vine that has infested many of the cooler parts of the Southeast, primarily forestland in the Appalachian Mountains. It is a serious threat to native plant communities due to its high reproductive rate and rapid growth. As a climbing vine it damages or kills native plants by girdling and shading. It can also hybridize with American bittersweet, leading to the natives loss of genetic integrity. Oriental bittersweet is native to Japan, Korea, and China.
Purple loosestrife Lythrum salicaria	A flowering plant introduced during the 1800s. It is found in all of the 48 contintiguous states. It chokes wetlands, replacing native shoreline vegetation.
Lespedeza Lespedeza spp.	Several species of these shrubs have become significant pests in forests and forest openings. Their dense leafy growth shades out all competitors. They are still being planted in some areas either as wildlife food or as soil rehabilitating (nitrogen fixing) plants. Seeds from these plants are spread by birds and new plants thrive under moderate to dense overstory cover, making them extremely difficult to control.
Japanese stiltgrass (Nepalese browntop) Microstegium vimineum	This grass is pervasive in disturbed lowlands. It can rapidly replace native ground cover in moist, fertile areas. At present, there is no efficient means of controlling Japanese grass over a large area, and the plant will continue to gain ground until new treatments are developed.
Privet Ligustrum spp.	Several species of privet are native to Europe, Asia, and North Africa, have been planted widely in this region as a hedge. Birds and other wildlife spread the seeds far and wide. Once it is established, privet can form dense thickets which displace native plants.Crews spend up to 550 work hours each year digging and spraying privet thickets in the Great Smoky Mountain National Park alone.
Mimosa Albizia julibrissin	This medium-sized tree is a continual problem along some roadsides and streams in the southern Appalachians. It seeds prolifically and resprouts quickly when cut. Mimosa seeds may remain viable for 50 years or more. The tree is native to Asia and was introduced to this country in 1745. Smoky Mountian park crews have spent up to 600 work hours per year controlling mimosa.
Garlic mustard Alliaria petiolata	This ground layer plant can tolerate shade, making it especially threatening to the Appalachians densely forested environments. When introduced to disturbed areas or streamsides it can completely dominate the ground layer within 10 years. It can also move from disturbed roadsides or trailsides to undisturbed forest. Garlic mustard is native to Europe. It can be controlled with prescribed fire as well as by applying herbicides, cutting, and hand pulling.

A more extensive list of nonnative invasive plantsin the Eastern United States can be found at www.invasive.org, maintained by The University of Georgia, the USDA APHIS PPQ and the USDA Forest Service Forest Health Technology Enterprise Team. This site contains a synthesis of recent publications by the USDA Forest Service, National Park Service, U.S. Fish and Wildlife Service, USDA APHIS PPQ, and the Southeast Exotic Pest Plant Council. It covers identification characteristics, distribution, and control options for 97 tree, shrub, vine, grass, fern, forb, and aquatic plant species that are invading the Eastern United States. For each species, a menu of control options is presented, including mechanical treatments, specific herbicide prescriptions, and, for selected species, recent advances in biological control.