Jan Newton, educational coordinator for the John Clayton Chapter, Virginia Native Plant Society ... www.claytonvnps.org ... suggests native plant alternatives to these non-native invasives:
Mimosa tree or silk tree (Albizia julibrissin) can grow in a variety of soils, produce large seed crops, and resprout when damaged, it is a strong competitor to native trees and shrubs in open areas or forest edges. Dense stands of mimosa severely reduce the sunlight and nutrients available for other plants.
Suggested Alternative Native Plant
Examples of native alternatives for silk tree (mimosa) are redbud (Cercis canadensis), flowering dogwood (Cornus florida), fringe tree (Chionanthus virginicus) and sourwood (Oxydendron arboreum). Also ironwood (Carpinus caroliniana) is a native tree that provides a shady environment.
Tree-of-heaven (Ailanthus altissima) is a prolific seed producer, grows rapidly, and can overrun native vegetation. Once established, it can quickly take over a site and form an impenetrable thicket. Ailanthus trees also produces toxins that prevent the establishment of other plant species. The root system is aggressive enough to cause damage to sewers and foundations.
Suggested Alternative Native Plants
Examples of native deciduous shrubs and trees that can be substituted for tree-of-heaven are staghorn sumac (Rhus typhina), smooth sumac (Rhus glabra), and black walnut (Juglans nigra).
Kudzu (Pueraria montana) kills or degrades other plants by smothering them under a solid blanket of leaves, by strangling woody stems and tree trunks, and by breaking branches or uprooting entire trees and shrubs through the sheer force of its weight. Kudzu plants rapidly grow rapidly as much as 60 feet per season. This vigorous vine may extend 32-100 feet in length, with stems ½-4 inches in diameter. Kudzu roots have massive tap roots 7 inches or more in diameter, 6 feet or more in length, and weigh as much as 400 pounds. As many as thirty vines may grow from a single root crown.
Suggested Alternative Native Plants
Native vines such as trumpet creeper (Campsis radicans), passionflower (Passiflora incarnata), coral or Clayton honeysuckle (Lonicera sempervirens), and native bittersweet (Celastrus scandens) have attractive flowers and fruits, provide food for wildlife and make excellent substitutes for kudzu.
Chinese privet or ligustrum (Ligustrum sinense) is a large shrub or trees that grows in sun to part sun and reaches 12 to 20 feet or more in height. Its leaves are evergreen, opposite, and somewhat pear-shaped with a sharp terminal point. In spring white flowers are borne on large terminal clusters 5-8 in long. The flowers produce a perfume that is not particularly pleasant as well as quantities of pollen that bother some folks. The flowers are followed by dull black berries which are then dispersed by birds and readily reseed in wild areas, becoming invasive. Dorothy Geyer with the Colonial National Historical Park Service comments that they have documented 787 acres of the Ligustrum sinense in the park and that it will be next on her list of invasive plants “to hit full throttle or to at least get it down to a manageable population.”
Suggested Alternative Native Plants
Mountain laurel (Kalmia latifolia), with its waxy, evergreen foliage and striking pinkish-white flower clusters in the spring is a beautiful substitute for ligustrum and it blooms more profusely in full sun than it does in part sun. Southern wax myrtle or southern bayberry (Morella cerifera), producing waxy blue-grey berries that are eaten by birds and other wildlife, offers scented, evergreen foliage as a nice alternative to ligustrum. Inkberry (Ilex glabra) is also a native alternative that produces waxy, evergreen leaves and its ink-black berries are eaten by birds.
In her own words, Jan Newton says:
U.S. native plants can become invasive outside their natural, historical ranges, be sure to use plant species native to the ecological region you live in. Check with your local native plant society, state forester or resource manager for recommendations of species and sources of native plants. Our local native plant society is the John Clayton Chapter of the Virginia Native Plant Society (www.claytonvnps.org).
Native plants may be able to stop invading species in their tracks, according to Invasive Plant Science and Management is a broad-based journal that focuses on invasive plant species.
Nature can have its own solutions to offer against invasive plant species, according to the journal.
In the case of the weed cogongrass, woody vegetation at the forest's edge may stop its progress. By catching seeds blowing in the wind, shrubs can prevent or lessen the impact of an invasion of weeds that will strangle native plants.
A study recently reported in an issue of the journal Invasive Plant Science and Management found that woody vegetation may form a natural barrier to the dispersal of seed. Cogongrass is an invasive species that displaces native vegetation and adapts to varying conditions of shade and moisture, making its spread hard to stop. Researchers put a natural barrier to the test against cogongrass.
Pine forests within the Gulf Coastal Plain of Mississippi served as the study site. Two kinds of barriers were tested: (1) frequently burned areas with an open canopy of pine and tallgrass understory and (2) areas that have not experienced frequent fires where there are closed canopies of pines and hardwoods with a dense midstory of shrubs and small trees. The study utilized three forest sites, each containing both barriers.
A minimum of 50 cogongrass spikelets were released at each location and allowed to be dispersed by the wind into the forest sites. Tallgrass sites saw more spikelets dispersed farther into the forest than sites with dense woody vegetation. The shrubs and trees served to reduce wind speed and intercept the spikelets before they could become established within the forests.
However, cogongrass that is already established may continue to spread on the ground, without the aid of the wind. Woody vegetation cannot defend against this type of invasion, and the study's authors recommend that forest managers use additional means of control.
Fire increased the spread of cogongrass in both types of study sites. This poses a dilemma for managers seeking to maintain more open forests for other reasons, such as biological diversity. The solution may be to "seal" the edges of the forests with woody vegetation while maintaining the open canopy within.
About Invasive Plant Science and Management
Invasive Plant Science and Management is a broad-based journal that focuses on invasive plant species. It is published four times a year by the Weed Science Society of America, a nonprofit professional society. The Weed Science Society of America promotes research, education, and extension outreach activities related to weeds; provides science-based information to the public and policy makers; and fosters awareness of weeds and their impacts on managed and natural ecosystems. For more information, visit http://www.wssa.net/