It’s not surprising that florists and arts and crafts folks like to add the vines of oriental bittersweet (Celastrus orbiculatus) to wreaths and other autumn decorations—the yellow leaves and orange berries are stunning. But this perennial vine is one of the worst invasive plants on North American soil. It’s a highly aggressive vine that spreads quickly, rapidly overgrowing anything in its vicinity, and killing even large trees.
All parts of the American bittersweet are poisonous to humans and pets. The berries are eaten by songbirds, ruffed grouse, pheasant, and fox squirrels.
Identification of Oriental Bittersweet
Introduced in the 1860s as an ornamental and erosion control plant, oriental bittersweet has escaped cultivation because it grows in full sun as well as shade, and in many locations, including meadows and grasslands, woods and woodland edges, along roadsides, and even on dunes and beaches. It is spreading rapidly in the Northeastern and Midwestern United States.
Oriental bittersweet is a deciduous, woody vine that can easily reach up to 100 feet. The glossy alternate leaves are round, finely toothed, and round or oval in shape with pointed tips.
In May or June, small, greenish yellow, five-petaled flowers appear in the leaf axils. The green berries ripen to a bright yellowish-orange in the fall, and the leaves turn yellow. The berries usually remain on the vine throughout the winter, often serving as an emergency food for birds which then spread the seeds further.
The woody vines coil arounds trees, shrubs, and any other support, including manmade structures. The roots of oriental bittersweet are deep and have a characteristic bright orange color.
|Botanical Name||Celastrus orbiculatus|
|Common Name||Oriental bittersweet, Chinese bittersweet, Asian bittersweet, Asiatic bittersweet, round-leaved bittersweet|
|Plant Type||Perennial vine|
|Mature Size||Vines can climb up to 100 feet or more up a tree and develop a seven-inch diameter|
|Bloom Time||May to early June|
|Native Area||China, Japan, Korea|
Why Oriental Bittersweet Is So Vicious
Oriental bittersweet chokes out and kills any other vegetation in several different ways. The vines completely overgrow other plants, so they won’t get any sunlight, air, or water. The strong vines girdle so tightly around the stems of trees that they are being strangled. As the vines grow, their sheer weight breaks or uproots the tree.
Oriental bittersweet produces an abundance of berries. Birds eat the berries and spread the invasive plant further through their droppings. The seeds remain in the bird's stomach for several weeks, which leads to the spreading of oriental bittersweet far away from its original location. On top of it, oriental bittersweet has a very high germination rate of 95%.
Oriental bittersweet also spreads by underground roots. If oriental bittersweet is not controlled, it will result in a monoculture, smothering everything else around it.
How to Get Rid of Bittersweet Vines
Small vines can be pulled by hand. Make sure to remove the entire root because bittersweet can regrow from root segments. Dispose of the vines in the garbage, or leave them on a manmade surface such as driveway, tarp or deck in full sun for a day or two to kill the roots.
If the vine is larger, and already entangled with the tree, cut the stem at the base and immediately brush the cut with glyphosate concentrate. Note that to be effective, this must be done during the growing season. Then carefully pull the vines out of the tree. If the vines are wrapped around the tree trunk or branches, removal is often not possible without causing damage to the tree. In that case, cut the vines out of the tree in pieces. In areas that are too high to reach, just leave the vines; they will die and shrivel over time.
After you have treated the cut surface with glyphosate, inspect the stump from time to time to make sure that it does not regrow new shoots, and reapply the herbicide as needed.
Oriental vs. American Bittersweet
Not all bittersweet is evil. There is also American bittersweet (Celastrus scandens), which is a highly desirable native plant.
American bittersweet occurs naturally in the central and eastern United States except in Florida. Consider yourself lucky when a native bittersweet plant pops up in your garden.
Unlike oriental bittersweet, American bittersweet has smooth stems and oblong leaves. Another way to distinguish between American and oriental bittersweet is by the location of the berries: the berries of American bittersweet appear at the tips of the vines only, while those of oriental bittersweet grow along the vine.
Unfortunately, American bittersweet is becoming increasingly rare. Further endangering it is the fact that oriental bittersweet sometimes hybridizes with the native species.