Now that the leaves have fallen, an orange cast is visible on trees and shrubs along the roads and in other places. This is from the fruits of Oriental bittersweet (Celastrus orbiculatus), an invasive deciduous vine. If you are blissfully unaware of the invasive nature of this plant, you might think these are beautiful. Well, they are, and that’s one of the reasons this plant was originally introduced into the United States as an ornamental in the 1860s. Unfortunately, it is invasive, spreading agressively into new areas and killing native plants by covering them or strangling them with its twisting vines. Its current U.S range includes the northeast and the midwest. http://www.nps.gov
Once you know just how damaging it is, it is really pretty amazing to notice how widespread it is. In addition to growing on trees and shrubs, it can grow on rocky outcrops, telephone poles, etc. Pictured is a quite beautiful vine growing on a telephone pole.
Oriental bittersweet can be identified using characteristics of its leaves, bark, flowers, fruit, and root color. The alternate, glossy leaves are broadly ovate to circular in shape and have toothed edges. They are 2-7” long and 1.25-3.5” wide. Small greenish-yellow flowers are present from May to June and are located both terminally and in the leaf axils. Fruits form in these locations and this habit differentiates Oriental bittersweet from American bittersweet which only produces fruits at the tips of the shoots. The yellow-orange fruit capsules appear from July through October and open at maturity to expose the reddish-brown seeds. Bark is light colored and smooth with a few lenticels. The outer surface of the roots is bright orange and this can aid in confirming identification when pulling young plants.
Photos from L to R: Columbia Univ., USDA Forest Service, Illinois Dept. of Natural Resources.
Control of Oriental bittersweet is difficult, especially once it’s well-established. Control measures include pulling, mowing, foliar herbicides and cutting combined with brushed-on herbicides for older vines. The best time to eradicate this plant depends on the age and number of vines to be removed and/or killed. Young vines can be effectively controlled using foliar herbicides or regular mowing. Foliar herbicides are most effective on low growing, dense patches. Early in the growing season, cut back young plants and allow them to regrow for about four weeks. Then spray the plants with an herbicide, carefully following all label instructions. Mowing is an effective method of killing young vines if done weekly. If mowing is only done 2-3 times per season it actually stimulates vigorous root suckering. If plants will be pulled, the best time to do this is before fruiting. If the plants are removed after fruit capsules have formed, bag the plant debris to keep the seeds from being distributed and growing into new plants. To kill woody, more mature vines, the most effective method is to cut the vine and immediately (within a few minutes) treat the cut stump with an herbicide using a sponge or brush. The best time of year to do this is late summer. Vines left hanging in trees will decompose within two to three years.
Please don’t be tempted to use Oriental bittersweet vines in decorations on the exterior of your home. Birds will eat the fruits and the seeds pass through them unharmed to germinate and help spread this plant. It is also illegal to transport, move or distribute this plant and other banned invasives in the state of Connecticut. When removing bittersweet plants for control, all plants that have fruits should be bagged and either disposed of in a landfill or left in the sun to bake long enough to kill the seeds. Help prevent the spread of invasive plants. Learn more about oriental bittersweet and other invasive plants of Connecticut at www.ct.nrcs.usda.gov/invas-factsheets.html or by calling the UConn Home & Garden Education Center toll free at (877)486-6271 or email us at email@example.com.