Bittersweet is an extremely vigorous woody vine that can grow dozens of feet, smothering the tops of small trees, strangling them, and pulling them down, similar to the southern kudzu vine. In large mature trees, bittersweet can wrap around the trunk, climb 60 feet or more and follow branches out in search of sun. Bittersweet is easy to identify in the winter after its leaves have fallen. Its trademark red and orange seeds may be scattered nearby, ready for springtime germination. It likes full sun but tolerates shade and is often found at field edges and open areas where it has both sun and trees to climb. Established vines can have dozens of branches growing six feet or more each year. Roots are a trademark bright orange.
Why it’s a problem
Bittersweet, native to Japan, Korea and China, was imported to the US in the late 1800s as an ornamental because of its showy red-orange fall fruit. It has no known biological control and tolerates a wide range of growing conditions. Its seeds are spread by birds and humans and geminate easily. It crowds out native plants and can completely cover trees, shrubs and small buildings.
What to do
Do not harvest the berries for decoration. Unfortunately, using the bright red and orange berries in wreaths and decorations helps distribute the seeds and spread the vine further. Also, don’t plant it.
Bittersweet is so vigorous that all but the smallest plants need multiple strategies to eradicate it. Just cutting the vines encourages them to send fresh shoots in the spring. In the winter, focus on large vines: cut them close to the ground and again several feet up to deprive any new shoots of a handy trellis to climb. Allow the severed vines above to decay over time, or pull them to the ground if that will not damage the tree. In the spring, pull or dig out small vines and seedlings, removing as much of their orange roots as possible. In late summer and early fall, cut large vines and, with a small paintbrush, carefully paint stumps with liquid herbicide. Spraying is usually not necessary and risks injury to other flora and fauna.
More information on invasive plants and the NOT WANTED campaign is available on the Granby Conservation Commission webpage