Invasive plants are a problem in our world, and the Cumberland Plateau is not immune.
Join me for the class “Invasive Plants on the Plateau” from 9-11 a.m. Monday, July 29, at the UT Gardens, Crossville: Plateau Discovery Gardens, at 320 Experiment Station Rd. off Hwy. 70 N.
Free preregistration is required at ccmga.org/.
Why is it important to know about invasive plants?
When non-native plant species are introduced into other parts of the world, they often are no longer subject to many of the natural biological mechanisms, e.g., diseases or predators, which moderate their growth in their native world.
Many of these foreign plants also produce numerous high viability seeds which are widely distributed by seed-consuming birds.
In the absence of natural controls, these species are considered invasive plants as they spread rapidly and threaten to crowd out and replace native plant species.
Because the danger of introducing non-native plants was not appreciated for a long time, many invasive plant species were inadvertently introduced into the United States often by the international nursery trade. Most, but not all, originated from East Asia, and many have been here for more than 100 years.
Now that they are so well established, it is often exceedingly difficult to eradicate them.
The following is an introduction to several of the more common invasive plants found on the Cumberland Plateau. Surprisingly, some of these noxious plants are still offered commercially, particularly on the internet.
To avoid inadvertently adding one of these to your landscape, preferable native alternatives are also recommended.
Chinese privet
The USDA classifies Chinese privet (Ligustrum sinense) as one of “the most highly invasive plants in the South.” However, it is widely sold commercially as a hedge-producing shrub for the home landscape.
Native alternatives. Black chokeberry (Aronia melanocarpa) is a good native alternative that can be used to produce a hedge.
American hazelnut (Corylus americana) and ninebark (Physocarpus opulifolius) are other native shrubs to use in place of Chinese privet.
Japanese honeysuckle
The Japanese honeysuckle (Lonicera japonica) is a fast-growing invasive vine which spreads rapidly at the ground level.
Unfortunately, it forms thick coils around and eventually strangles any shrub or tree that it encounters. Once established, it is exceedingly difficult to irradicate.
Native alternatives. Coral honeysuckle (Lonicera sempervirens) is a very desirable alternative. It serves both as a protective habitat for nesting native birds and small mammals, including rabbits. In addition, its red trumpet-shaped flowers provide a rich nectar source for hummingbirds and native butterflies and bees.
Morrow’s bush honeysuckle
Morrow’s bush honeysuckle may be the second most common invasive bush found on the Plateau.
As the common name implies, it is a bush with multiple woody stems. The stems are hollow, light in weight and have deep longitudinally oriented groves in the bark.
In summer, the bush produces large numbers of bright red berries. Although they have little nutrient value, the berries are eaten by birds which scatter the seeds widely. As a result, within a brief time, the whole surrounding area is littered with large bush honeysuckles. Although they may look tasty, bush honeysuckle berries are toxic to humans.
Native alternatives. American beauty berry (Callicarpa americana) is an excellent native alternative to bush honeysuckle as it produces clumps of red-purple berries in late summer and are a choice food source for a wide variety of wildlife.
Winterberry (Ilex verticillate) is another excellent native alternative to bush honeysuckle. Winterberry is diecious with separate female and male plants. Although they both produce flowers, only the female plant produces bright red berries after fertilization by the male. Without berries, female and male winterberries are difficult to differentiate. Therefore, it is recommended to buy winterberry plants only from nurseries which specialize in native plants and offer both female and male winterberries.
Coral honeysuckle is also a very desirable native alternative to Morrow’s bush honeysuckle.
Multifloral rose
Multifloral rose (Rosa multiflora) is a very fast-growing thorny invasive bush. It also climbs, can become tall, and spreads everywhere.
Although it produces multiple small white flowers in the spring, these only bloom for a short time.
Once established, the plant is difficult to irradicate. However, it is commercially available, and because of its thorns and speed of spread, it is sometimes advertised as a “living fence.”
Native alternatives. Carolina rose (Rosa Carolina), and mountain laurel (Kalmia latifolia) are better alternatives. They do not have noxious thorns but produce an abundance of attractive and longer-lived white flowers. Carolina rose prefers sun to partial shade while mountain laurel thrives best in the more dappled light conditions found on northern-facing slopes.
Tree of heaven
Tree of heaven (Ailanthus altissima) was introduced from China as a tall rapidly growing, ornamental shade tree with an absence of insect problems.
However, a very rapid rate of growth and the massive bundles of seeds produced by mature trees make tree of heaven “the most invasive tree in the South.”
Tree of heaven also produces massive roots which cause sidewalks to buckle and water lines to break.
Native alternatives. Winged, webbed, or shining sumac (Rhus copallinum) is a desirable native alternative. It produces abundant clusters of white flowers in mid-summer which attract native pollinators, particularly native bees.
Soaking the seeds of shining sumac produces a refreshing lemonade-like drink.
Bradford pear
Bradford or Callery pear is an ornamental tree which produces attractive white blossoms in the spring and for decades was widely planted in new suburban developments.
It was initially advertised as non-fertile. However, it does produce small fruits which are spread by birds and as a result is an incredibly invasive tree.
New rapidly growing sprouts appear everywhere: on roadsides, in parks, fallow fields, and in recently abandoned homesites. The wood is brittle and frequently susceptible to wind damage.
Bradford pear also produces a strong disagreeable pungent smell, particularly when blooming in spring.
Native alternatives. Native fruit trees including American plum (Prunus americana) and serviceberry (Amelanchier laevis) are much more desirable alternatives. They both produce abundant white blossoms in spring and tasty fruits in the fall.