Yes, bittersweet looks pretty sweet when dressed in its autumnal red-and-gold berries, which around here ripen in October and November. The berried branches do make sweet Halloween and Thanksgiving decorations. But here’s the bitter part of this plant: it’s a killer. It murders trees by choking, toppling and smothering. Bittersweet climbs trees by coiling its stems around the trunks. As the vine’s twining stems expand, it becomes a noose that chokes the tree to death. That is if the weight of the invasive vine’s branches and foliage hasn’t already toppled the tree in a storm. Vines that reach the tree tops cascade over the branches, blocking out sunlight and shading and smothering the trees.
Naturalists have observed Oriental bittersweet growing and reproducing so fast that it can destroy a half-acre woodlot in seven to 10 years. If you’re counting on selling that wood, don’t let the timber get wasted by these vines. If you own land that you rarely visit, be advised to check it out as soon as possible for bittersweet invasion because this killer vine is on a relentless rampage in Virginia. It has recently been found in more and more places in Greene County.
Birds spread this invasive vine. They eat the colorful fruits and then poop the seeds beneath the trees where they perch, perhaps miles away. Uneaten berries drop to the ground where they can germinate and intensify a local infestation. The vine also spreads by underground roots, once established, which causes it to form a thicket. The stems that sprout from the root system are slender, dark reddish-brown and somewhat prickly, definitely not fun to encounter.
The time to start controlling bittersweet is now—don’t wait until fall when you see the showy fruits high up in your trees. All those fruits represent potential new plants and it’s too late to do anything about them once they ripen. Bittersweet berries start out green, ripen to red and then the red shell splits to reveal an orange center. Not all vines have berries, because there are separate male and female plants. You’ll want to wipe out the nonfruiting male ones, too.
Learn to recognize Oriental bittersweet when it’s a green vine without bright berries. Its bright green leaves are 2 to 5 inches long, rounded to oval, with fine teeth along the edges and points at their tips. The leaves are widely spaced in a distinctive alternating pattern on the stems. A young vine shoots up in a spiral in search of something to grab onto and climb.
Once you learn to recognize this idiosyncratic, young growth stage, you’ll start noticing vines popping out of roadside vegetation, at the bases of trees in your woods, and even in your garden beds. Older vines are easily identified by the leaf shape and rough spotted bark pattern on stout, twisting, light-brown stems. (Poison ivy and Virginia creeper, both natives, have hairy roots along the edges of their vining stems; Japanese honeysuckle has shredded, light brown bark, and native grape vines have shredded, dark brown bark.) Bittersweet foliage usually remains green when native trees change into fall color, and then turns bright yellow after most trees lose their foliage for the year. This is a good way to identify vines and still a great time to control them.
Hunt for Oriental bittersweet along forest edges, in clearings, garden beds and borders and along fence rows. Be especially vigilant at the bases of trees. You can effectively rip vines from the ground if the soil is moist by gripping the crown and twisting and tugging. Be sure you get the entire root system. Any roots left behind can resprout. You’ll know you have the correct species if you see orange roots. Even small seedlings exhibit orange roots. Hand-pulling works well for small vines, but large vines require stronger methods. Cut stems that are one or more inches in diameter and spray the cut surface with undiluted concentrated herbicide in a labeled spray bottle used only for that purpose. You can also use a foliar herbicide on the leaves of small vines; spray as much of the foliage as you can without spraying overhead. Avoid spraying desirable plants.
The sweet part of this story is that if you are vigilant and search and destroy Oriental bittersweet vines, you can save your trees and savor your victory. But the unfortunately bitter part is that this nonnative invasive vine is now so widespread that you may have to keep after it for years to come, because it will move from your neighbor’s property to yours in a heartbeat—or should we say a bird’s flight?
Susan Austin Roth is a volunteer with the Blue Ridge PRISM, a nonprofit dedicated to controlling non-native invasive species.