Oriental Bittersweet is a rapidly spreading deciduous, twining vine with alternate round, glossy leaves. Small greenish flowers occur in clusters in the leaf axils. The leathery capsule surrounding the seed turns a bright orange in the fall. Oriental bittersweet occurs throughout Indiana and can overrun natural vegetation, forming nearly pure stands in forests. It can strangle shrubs and small trees, and weaken mature trees by girdling the trunk and weighting the crown. There is some evidence that it can hybridize with American bittersweet, thus threatening the genetic integrity of the native species. Note – do not buy, sell, or plant oriental bittersweet.
In 100 Years of Change in the Distribution of Common Indiana Weeds by William and Edith Overlease (2002) ) reported that oriental bittersweet was not recorded in Indiana in 1899 (Coulter’s Catalogue of Indiana Plants) or in 1940 (Deam’s Flora). In 2002, Overlease noted that oriental bittersweet had spread in the following 37 counties in Indiana: Brown, Clark, Crawford, Dubois, Elkhart, Floyd, Greene, Hamilton, Hancock, Harrison, Jackson, Jasper, Jefferson, LaGrange, Lake, La Porte, Lawrence, Marion, Marshall, Martin, Monroe, Parke, Perry, Porter, Posey, Putnam, St. Joseph, Scott, Spencer, Starke, Sullivan, Switzerland, Vanderburgh, Vigo, Warrick, Wells, and White. Overlease noted that it “will be a major future pest in Indiana. It is readily spread by birds and has abundant crops of fruit. It has already become locally abundant in some areas.”