A Guide To Knowing Nonnative Species
By Marlee Moore
Kudzu may be the plant that snarled the South, but it’s just one of the nonnative invasive species running rampant across Alabama.
“Unfortunately, invasive species will be around for a long time,” said Dana Stone, the Alabama Forestry Commission (AFC) Forest Management Division director. “Some invasive plants have fewer occupied acres but are very devastating to the forest environment when present.”
Registered forester Brian Agnew agrees. He said many nonnative invasive plants were brought to the U.S. as ornamental flora or for erosion control. Exotic plants aren’t created equally and aren’t innately problematic — until they escape cultivation, spread and aggressively replace native species, he said.
For forest landowners, Alabama’s Top 5 most damaging invasive plants are cogongrass, tallowtree, Chinese privet, kudzu and Japanese climbing fern, according to Stone and Alabama Extension’s Dr. Nancy Lowenstein, an invasive plant specialist. While it’s not an exhaustive list, it gives landowners a starting point.
“Eradicating nonnative species is a long process and may be close to impossible,” said Agnew, who serves on the Bullock County Farmers Federation board. “But you have to try to control them.”
Stone, Agnew and Lowenstein suggest contacting industry professionals — such as registered foresters, Extension experts or AFC staff — to accurately identify and combat invasive plants.
Cogongrass is an aggressive, intrusive plant first introduced to Mobile in the early 1900s from Asia. Cogongrass has thick, extensive, hard-to-kill rhizomes and is a federal noxious weed (which means authorities can implement quarantines and take other actions to contain or destroy the weed and limit its spread).
The tall, perennial grass forms dense, circular infestations and is highly flammable, reaching temperatures that can kill longleaf pines. Silvery-white flowers bloom in spring or early summer.
Cogongrass can reproduce by dandelion-like seeds, but most new infestations occur when rhizomes are transported to a new location.
Experts recommend cleaning vehicles and equipment in the field if working near cogongrass to limit its spread. Select weed suppressants can be effective against cogongrass. However, they are generally situation-specific and require multiple treatments.
Also called the popcorn tree because of its off-white waxy seeds, a mature tallowtree can produce 100,000 seeds, which are viable in soil for up to seven years. Storms, water, wind and birds have caused tallowtrees to infest wetlands, as well as upland forests, especially in south Alabama. The tree, which has bright fall foliage, can reproduce by surface root sprouts.
Brush mulchers or shredders effectively open dense stands and can be a good first step to managing tallowtree invasion. However, follow-up treatments are necessary. It’s native to Eastern Asia and was introduced to the U.S. in the 1700s.
Chinese privet creates dense thickets in forest understories, preventing other vegetation from growing. Privet has opposite, leathery, oblong leaves with a pointed tip. Many small, white and fragrant flowers appear April to June.
Privet produces numerous seeds spread by birds, wind and other animals. The mostly evergreen shrub was brought to the U.S. in the 1850s and continues to be spread and planted as an ornamental shrub.
Plants can be controlled by hand pulling, weed wrenching, brush mulching and suppressant applications during specific stages of growth.
Kudzu can grow a foot a day in the summer, overwhelming trees, buildings, fences, road signs, poles and more. It eventually grows over other plants.
Kudzu was planted extensively in the South in the early to mid-1900s for forage and erosion control. However, its extensive roots and underground tubers make the Chinese native difficult to eradicate. Those roots and tubers must be killed before kudzu can be controlled. To stop new kudzu vine growth, cut just below the root crown and remove from the soil.
To control kudzu by repeated mowing or cutting, cut every vine to the ground. Then repeatedly cut or mow until it no longer regrows.
While several products are labeled for kudzu control in forestry and rights-of-way, a limited number of suppressants can be used for residential control.
Japanese Climbing Fern
At first glance, Japanese climbing fern looks like a vine. However, the fern produces thousands of tiny spores that are dispersed by wind and rain. It can also reproduce by rhizomes.
Japanese climbing fern is native to Asia and Australia and was introduced to the U.S. in the 1930s. Careful prescribed burns can reduce vines, and herbicide applications to foliage can control underground stems. However, Japanese climbing fern can also create fire ladders, where fire moves upward into a canopy of trees.