By Sally Wencel
An important aspect of natural landscaping or ecoscaping is using plant material that supports healthy ecosystems. The Tennessee Valley Chapter of Wild Ones promotes using native plants and naturally occurring plant communities to create and restore wildlife habitat (as well as for our own aesthetic enjoyment).
That doesn’t mean that the Tennessee Valley Wild Ones is “against” using non-native plants except for plants that qualify as invasive exotic pest plants. We recognize that the vast majority of non-native plants, about 85%, cause little if any environmental damage other than taking up space that could be occupied by native species. These plants politely occupy their place in the landscape and pose little threat to natural areas. Our food supply is even primarily made up of exotic species. But some “exotic” plants are not so innocent. Once removed from their native habitats, these exotics begin to reproduce abundantly in their new settings, causing significant environmental disruption.
Why do some exotic plants become invasive? For the most part, these plants have competitive advantages over native plant species that often include:
- an absence of the insect predators and plant diseases that helped to keep their numbers in check in their homelands
- a longer growing season that allows them to shade out native plants before the natives have a chance to grow, or to take more than “their share” of moisture and nutrients from the soil
- an astonishing ability to re-produce and form colonies in disturbed soil due to rapid growth rates and massive seed or shoot production
- the capacity to adapt to a wide range of growing conditions
- effective means of spreading
And why should we care about invasive plants? Some horticulturalists defend introduced plant species as often providing benefits, call native plant proponents xenophobes and even suggest that we “learn to love them.” Contrary to this cosmopolitan viewpoint, invasive exotics do degrade the environment and impose a hefty cost. Specifically, invasive exotic plants:
- have no natural controls to limit their growth
- compete with native plants for space, sunlight, nourishment and breakdown the natural communities
- by replacing native plants, can limit or reduce the quality of food and shelter available to wildlife
- can harbor fungi, pathogens, varmints and other organisms that can be harmful to native plants and animals
- reduce biodiversity by taking over natural communities
- can be highly expensive to remove
What are some of the biggest pest plants growing in the Tennessee Valley? The obvious answer might be Kudzu, which is a huge problem along many woodland edges and roadways and its invasion is quite visible. However, many residents are not aware that some plants still available in local nurseries are considered major threats to natural areas because of their rapacious growing habits and high seed dispersal. Among the biggest pests are Privet (all species), Tree of Heaven (Alianthus altissima), Mimosa (Albizia julibrissin), Princesstree (Paulownia tomentosa), Autumn Olive (Elaeagnus umbellata), Japanese honeysuckle, Exotic bush honeysuckles, English ivy (Hedera helix), and Japanese Knotweed (Polygonum cuspidatum). The Tennessee Exotic Pest Plant Council has a complete list that can be found on its website.
In addition to resources listed elsewhere, we have developed materials to help you identify invasive exotic pest plants, native plant substitutes and how to remove these pests from your landscape.