Non-native Invasive Plants: A Growing Threat to our Environment By Nancy J. Loewenstein, Research Fellow, Auburn School of Forestry & Wildlife Sciences

Non-native invasive plants are one threat to our environment we should all become more familiar with because we may inadvertently be adding to the problem. Plants are considered non-native if they were introduced to an area by human activity, either accidentally or purposely. Most non-native plants are not harmful. In fact, many of our agricultural crops and ornamental plants are non-native and are quite beneficial to our economy and well-being. However, some of these plants escape cultivation and become weedy pests. Kudzu is probably the most infamous non-native invasive plant in Alabama, but it certainly isn't the only invasive plant pest we need be concerned about.

(Photo courtesy of Wikipedia: Kudzu plant in bloom)

Invasive species are a concern because they can literally overrun native species, which reduces numbers, including the biodiversity of native plants and the insects and animals that depend on them. Infestations of invasive species can also change the way ecosystems work, altering fire regimes, water cycles, soil characteristics, and the regeneration of forests and other natural areas. Infestations also reduce forest productivity, impact wildlife, and hamper hunting, fishing, and other outdoor activities.

In addition to harming the environment, the control of invasive plants costs billions of dollars each year. The elimination of infestations often takes years of herbicide applications and/or back-breaking work cutting down or pulling out plants. Preventing the establishment of invasive plants or catching an infestation while it is still small, is one way to help slow the spread of such plants across the landscape.

The first step in controlling invasive plants is learning which plants are invasive and what characteristics make them invasive. A list of invasive plants in Alabama can be found on the Alabama Invasive Plant Council's website at www.se-eppc.org/alabama/. Many of the plants on the list are ornamental plants that have escaped cultivation. Some of the trees included on the list are:

silktree or mimosa (Albizia julibrissin), princess tree (Paulownia tomentosa), Bradford pear (Pyrus calleryana) and Chinese tallow tree (Triadica sebifera). Several ornamental shrubs on the list are: thorny olive (Elaeagnus pungens), heavenly bamboo (Nandina domestica), Chinese privet (Ligustrum sinense) and glossy privet (Ligustrum lucidum). Invasive ornamental vines include English ivy (Hedera helix), Japanese honeysuckle (Lonicera japonica) and Chinese wisteria (Wisteria sinensis).

Characteristics that many invasive plants share are rapid and aggressive growth, production of numerous seeds that are spread easily by birds or water, and the ability to grow under many different conditions. This is not to say that all plants with these characteristics are, or will become, invasive. However, since it may take decades for a plant species to become a recognized invasive pest, it is best to be extra cautious when growing plants that share the characteristics listed above.

Invasive plants do not respect boundaries, which is why making wise choices about landscaping is so important. Managers of natural areas suggest that you consider not planting known invasive species in your yard, especially if you live near the edge of town or out in the country where seeds and/or aggressive plants can easily spread into nearby woods, fields, or other natural areas. Contact your local Extension agent or the author for additional information about invasive plant control.

More information about invasive plants is available online at:

Southeast Exotic Pest Plant Council
Invasive.org
The Nature Conservancy
National Invasive Species Information Center

References

Hoyle, Zoe. (Spring 2005). Silent invaders of southern forests. United States Forest Service Southern Research Station. Compass, 1(2), 1-5.

United States Fish and Wildlife Service. Invasive plants in our backyards. Retrieved March 5, 2007.

Plant Conservation Alliance. Weeds gone wild: Alien plant invaders of natural areas. Retrieved March 29, 2007.

The United States National Arboretum. (March 29, 2006). Invasive plants. Retrieved March 5, 2007.

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