Oriental bittersweet might just be the "kudzu of the north". Since its introduction in 1860 as an ornamental plant, it has spread from Maine to North Carolina. Like kudzu, it's a vine that can grow over the tops of trees and cover fields. Oriental bittersweet grows in forests, along roadsides, and in open fields. It also grows along sand dunes and could lead to increased beach erosion. Oriental bittersweet can establish in shade and will grow rapidly in full sun. The vines twine around trees often killing smaller trees. The weight of the vines in the tree canopy make the tree susceptible to wind damage.
All photos in this article by Jil M. Swearingen, USDI National Park Service, Bugwood.org
Beware the Bright Orange Fruits
Oriental bittersweet is often used in wreaths and dried-flower arrangements because of its bright orange and red fruits. The fruits grow in small clusters all along the stems. The seed is covered in a bright orange-red coating which is revealed when the papery yellow capsule surrounding it opens in fall. Birds eat and disperse the seeds.
American Bittersweet Loses Ground
There is a native American bittersweet that looks similar to Oriental bittersweet. The native bittersweet has larger clusters of fruits that only grow at the tips of the branches. It is being pushed out by Oriental bittersweet though and may hybridize with Oriental bittersweet.
Controlling Oriental Bittersweet
If you use bittersweet as a decoration, be careful only to use it indoors and dispose of it in the trash so that seeds will not escape. Pull up small plants as you find them. Larger vines are more difficult to kill. Like many woody plants, Oriental bittersweet can be controlled by cutting the stems and painting the cut ends with a concentrated herbicide containing glyphosate or triclopyr. In areas where it's dense, a more diluted herbicide containing triclopyr can be sprayed on the leaves in late summer through early fall for best control. The vines can also be cut back in early summer and the new growth sprayed a month later. If Oriental bittersweet is growing on flat, open ground, it can also be controlled by mowing once a week during the growing season. Mowing less often, though, will encourage new sprouts to form.
Article by Sylvan Kaufman. Dr. Kaufman is a writer of popular scientific and gardening articles. She is also an ecological consultant.
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