By: Pat Ludwig
Imagine we’re strolling along a trail and notice vines snaking up and around the trunk of a young tree or shrub. We do a double take, as something doesn’t look normal, and notice the vine is actually cutting into the bark of the stem of its host. The vine is smooth with light tones of grey and tan, and the leaves are simple (i.e., a single leaf attached by its stalk) and rounded with slightly wavy edges and a pointed tip. Perhaps we’re seeing the vine in the spring or early summer and notice flowers appear at the leaf joints or we see the vine mid to late summer and notice berries all along the branches.
We recognize this as the invasive Asiatic (Oriental) bittersweet vine that eventually kills its host plant by constricting their stems and blocking sunlight. Beyond harming individual host plants, this prolific vine poses a serious threat to entire plant communities, as its rapid growth, abundant berries, and ability to spread from its orange-colored roots allow it to overtake native shrubs and trees, blocking out sunlight and reshaping woodland habitats.
Here in Connecticut, there’s a similar looking plant, the native American bittersweet. It has finely toothed leaf edges, with flowers and then the berries forming only at the end of its branches. The Native Plant Trust lists the American bittersweet as rare and of “special concern” in Connecticut. The native can grow as a vine or form a small shrub with several stems growing from the base of the plant. Our native bittersweet can reach heights of 30ft and the stem 3 inches in diameter. The native and the invasive can hybridize, and if we have both we certainly want to manage the invasive carefully. The iNaturalist app and GoBotany.org are reliable sources to confirm you are pulling or cutting the invasive, and not the native, plant.
Perhaps you’ve identified Asiatic bittersweet on your property and want to manage the invader. A reliable information source is the CT Invasive Plant Working Group (https://cipwg.uconn.edu), which has a calendar indicating how and when to do specific types of invasive species management. Currently, the science indicates you can pull the relatively shallow roots throughout the year, which is easiest when the soil is moist. If you choose to use herbicide, you can effectively cut and ‘paint’ herbicide on the (fresh) stump mid-July to the end of October. Refer to the CIPWG website for the correct herbicides and amounts. Ideally you do not want the vine to produce berries, as these are spread by both birds and wind, yet herbicides aren’t effective until the same time the vines fruit. One approach to avoid this dilemma is to cut the vine before July and mark the location, then return in mid-summer to make a fresh cut and apply herbicide to the stump. Foliar herbicide application (i.e., spraying herbicide directly onto the leaves) is worth avoiding, as it is more likely to harm pollinators.
Both native and non-native bittersweet are commonly harvested for wreaths and seasonal decorations–just be mindful to dispose of any berries carefully, as they can spread the plant to new areas. Some have even shaped the cut vines into peace sign wreaths, a fitting bit of humor after the hard work of invasive plant management. Locally, the vines have been used in displays such as the decoration at Middletown’s Clocktower Plaza entrance.