Move over, kudzu: Oriental bittersweet and a grab bag of other non-native, invasive plants may actually pose more of a threat to our Southern forests. Like kudzu, Oriental bittersweet can rapidly overwhelm native plants by covering and choking them. But unlike kudzu, which tends to be limited to sunny, open areas along roadways, Oriental bittersweet can pop up deep in the woods: About 3,600 acres of public lands in the Southeast, including the Pisgah National Forest, have been blanketed by the invader.
That's because Oriental bittersweet has a very effective proliferation system, says Bob Gale, an ecologist with the nonprofit Western North Carolina Alliance: "Birds love the berries, [which] don't provide a lot of nutrition. It's kind of like eating junk food."
And birds deposit those seeds in places where many native plants — including Virginia meadowsweet, a rare member of the rose family — are already threatened or endangered, Gale explains. He coordinates volunteer teams that inventory and remove exotics, most recently along the Cheoah River near Robbinsville. "Earlier this year, we did some kudzu control on a small island on the Cheoah," Gale reports.
By "control," he means laboriously pulling, trimming and removing the vines by hand or by mechanical means. Another possible approach involves biological agents. An experimental kudzu-removal project on Roan Mountain uses goats, but that wouldn't work on the Cheoah: Hungry goats don't distinguish between Oriental bittersweet and the Virginia meadowsweet that's been discovered there, Gale points out.
For Gale, the last resort is herbicides. About four years ago, he recalls, he worked with trained volunteers to inventory, study and remove exotics near the Appalachian Trail at Lovers Leap in Hot Springs. Part of the work included mapping the findings with a GPS device. It was a collaborative effort involving federal and state agencies, nonprofits such as the Appalachian Trail Conservancy, and an Asheville-based business, Equinox Environmental, says Gale.
On that particular trip, Gale teased a 15-foot bittersweet root out of the soft forest soil near the trail, challenging his volunteer team to do better. A little bit later, they came out of the woods with an intact, 40-foot-long root.
Unfortunately, the stuff grew back. Here in the mountains, the natural enemies that limit exotics' growth in their native habitats — diseases, climate conditions and such — aren't present, Gale explains. "The reality is, unless you're working in your own backyard and can go at it every day, you're going to have to use herbicides," he concedes.
On the Cheoah, the team used a triclopyr-based product that "breaks down quickly before it moves anywhere," stresses Gale. Typically, one team member cuts the bittersweet along its woody stem and another applies the herbicide to the cut, where it will be absorbed into the plant. This targeted approach helps avoid large-scale spraying that would damage other plants, and — especially when applied at the end of the season — it reduces growth the following year, he reports.
But the real key, notes Gale, is public education and collaboration — in his case, with such partners as the Tennessee Valley Authority, the North Carolina Department of Transportation, the U.S. Fish and Wildlife Service, Alliance volunteers and many others. Through a variety of ongoing, joint projects, volunteers learn all about the invasive species, often returning home to discover they've got them in their own yards, he says.
Lindsay Majer of Equinox remembers once staying at a bed-and-breakfast and talking to the owners about her work. "The owners said, 'We've got a vine in our backyard that's really taking over.' It was Oriental bittersweet." A few years earlier, it turned out, the owners had bought a decorative, berry-laden wreath for the holiday season and then tossed it on the compost pile afterward. "Now it's a big bittersweet problem, and they live next to the forest," says Majer.
Here in Western North Carolina, a 2001 study by the Southern Research Station at Bent Creek concluded that such human sources has made Asheville "the mother lode for most of these invasives," adds Gale. "They come in from here and spread out," he says.
Wind, water, birds, a hiker's boots, the blades of a highway mower — all can help spread invasive plants. The U.S. Forest Service's most recent Nonnative Invasive Plant Species inventory lists 33 species, from the popcorn tree to garlic mustard and English ivy. More than 18 million acres of Southern forests are affected, according to a 2008 Southern Research Station report.
Says Gale, "There's no end of places to work."
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