Invasive Species In The Southeastern US: Four Elegant Invaders
What is an Invasive Species?
Invasive species: a living organism not native to an area, but rather introduced artificially either by plan or accident; sometimes called exotic pest plant and animal species.
In April, I can't help but just love the sight of Wisteria at the edge of the woods and fields. Purple clusters hang elegantly from twisting vines and the blossoms smell divine. But as the saying goes, "beauty is only skin deep." Or in this case, only bark deep. You see, this graceful, aromatic vine is what is known as an invasive species.
An invasive species is any member of the plant or animal kingdom that invades an area it is not indigenous to. And although they may look quite elegant or serve the purpose of erosion control like Kudzu, they are still right up there on the invasive species least wanted list.
Why is an Invasive Species a Problem?
But be mindful, not all invasive species are problematic; for example, dandelions. Dandelions are nice little weeds that generally mind their own business and don't take over an area. They are good for attracting pollinators to the garden, are edible and have several health benefits.
When an invasive species escapes cultivation and runs rampant through the countryside, it becomes an exotic pest. Spreading quickly, it competes aggressively with native species. The native wildlife may not have had a chance to evolve defenses against these invaders. They prey on the native species, out-competing them for food and needed nutrients. This can happen in the animal kingdom as well as the plant kingdom.
Today, we know that biodiversity is threatened by some invasive species. About 42 percent of endangered species are at risk because of an invasive species. Still, some invasive ornamental plants are sold commercially. Getting them under control can take years of expensive herbicidal applications and extensive pulling, mowing and mulching.
How Are Invasive Species Introduced Into a Region?
Species in the United States considered invasive have their roots in the colonial days. Colonists, unaware of the notion of invasive species brought many of their favorite specimens of flora and fauna with them to the new colonies. Although they were useful, many have become problematic over time. They were also carriers of some diseases and insects. Some of the species the early colonists brought over include Queen Anne's lace, dandelions, horses, cows and domestic pigs in New England.
Sometimes an invasive species has been brought over for a specific reason. This is called intentional introductions. They may have been intended for biocontrol and released into the wild where they caused unexpected problems. Some animal species may have been intended to be pets and escaped into the wild.
Other incidences of evasive species are unintentional introductions. Mail ordering items over the internet is the newest way for an invasive species to enter an area. Ships can carry aquatic organisms in the ballast water. The dreaded woolly adelgid, an insect that is destroying the eastern hemlock got to the United States by ship transport. Trucks and trains can transport organisms over land on the same continent. The pet trade industry may be responsible for introducing an invasive animal. Snakes and other exotic pets may get dumped by owners because they outgrew their tanks or cages. As far as plants go, the nursery trade industry may be responsible, as is the case with Kudzu.
What Other Places on Earth Have Invasive Species?
The answer is everywhere. In the United States, invasive species have spread through all the woodlands, desserts and wetlands. Places that are transportation hubs tend to be the hardest hit. Around the globe, birds, herbs, trees, grass, shrubs, insects and mammals find their way into new territory. The extent to which they become problematic depend on several factors or traits that the plants may have.
What can you do to help control an invasive species?
First, make yourself familiar with what species are considered invasive in your area. Google or check with your local agricultural extension agency. You may choose to try and use chemical (herbicides), physical removal (pulling, uprooting) or a combination of both. Grants may be available to help you eradicate your property of an invasive species. When traveling, clean all recreational equipment thoroughly. If driving from one part of a continent to another, don't transport fruits, vegetables, nursery plants, flowers, limbs, leaves. Don't purchase any ornament invasive species.
Traits of Invasive Species
An invasive species will have one or more of these characteristics:
- reproduces rapidly and at a high rate
- disperses seeds prolifically
- can colonize areas after they have been disturbed
- great genetic variability
- live long lives
- closely associated to humans
- single parent reproduction
- vegetation or cloning reproduction
- abundant in its native land
- has a broad diet
Wisteria is a member of the pea family. The small purple blooms that hang in clusters are shaped like pea plant blossoms. It is popular as an ornamental plant in its native China and Japan because of its pretty purple blossoms and lovely smell. Wisteria is not invasive everywhere, but it is rampant in the Southeastern United States where it has the ability to take over and choke out native plants. You can find it most anywhere in the early spring including parks, empty lots and at the edges of the fields and woods.
Scotch Broom is also a member of the pea family, except it is a shrub where Wisteria is a vine. It has the same shaped petals as the Wisteria. It is native to Europe. They are a brilliant, bold yellow. It grows in dry, open meadows and along roadsides. The stems and tiny leaves of the Scotch Broom plant are evergreen. I'll have to admit, it is an elegant looking plant, and I have used the stems as filler in holiday floral arrangements. However, it is highly invasive and is said to negatively effect wildlife in the Southeastern US. It blooms at the same time as Wisteria. It is mildly toxic to horses and similar animals. It has been used as an herb for medicinal purposes.
With its pretty pink leaves in spring that turn green and stay green all winter, the Nandina bush became popular in landscaping during the 1950s and 1960s. It has white blossoms in spring that turn into showy red berries from autumn through winter. An elegant-looking shrub, Nandina is native to Eastern Asia. But in the United States, it has hit the most unwanted list in North Carolina, Tennessee, Georgia and Florida. The problem is shoots that travel underground, causing growth to become out of control.
Kudzu was introduced into the United States by Japan in 1876 at the Centennial Exposition in Philadelphia. In China, it is one of 50 essential herbs for medicinal purposes. It has been shown to be useful in the treatment of migraine and cluster head aches, allergies and diarrhea. Kudzu has proven useful over the years for preventing soil erosion in the hilly parts of the southeast where it grows prolifically. It is an interference competitor because it blocks out light to other vegetation. It is edible, but not recommended for consumption because of herbicides. It has been used for forage for grazing animals. Kudzu reproduces by vegetation reproduction and occasionally by seeds. Seeds can take years to germinate, causing some to think it has been eradicated only to reappear.