There is nothing "sweet" about Oriental bittersweet. This non-native species appears to be popping up, and then growing up, in NW Ohio. While it was an occasional invader in natural areas, forests and fence lines, more and more people are having to manage this invasive species. For several years there was a small stand near the office that I would collect for programs and use for plant identification and diagnostic training. It seemed to be pretty well behaved, not spreading like a wildfire, but a consistent source for my programming needs. Well last year, it really began taking off. It was twisting and twining its way up and over landscape plants and becoming a real problem that will need to be managed or there could be a monoculture of Oriental bittersweet in the future.
Oriental bittersweet is invasive vine that is native to China, Japan and Korea. It was introduced to the United States as an ornamental plant around 1860. This deciduous, woody, twining vine can climb on trees, shrubs and anything else in its way. The leaves are alternate, glossy and finely toothed. They are usually rounded, but there can be variation in the leaf shape. Stems are light brown with white pith. Roots are bright orange in color. The flowers of this vine are greenish and have five petals. Male and female flowers usually occur on two separate plants, and bloom time occurs in May - June.
The plant is well-known for its bright fruits. Stems and red and orange fruits are cut in the fall and commonly used a natural decorations which can lead to plant "popping-up" in new locations.
There is a native bittersweet (Celastrus scandens). It has more elliptical shaped leaves, rather than the rounded of the Oriental bittersweet. American bittersweet can also be distinguished from Oriental bittersweet by its leaves when they are just beginning to emerge from the bud. Oriental bittersweet leaves are folded flat along the mid-vein, whereas American bittersweet leaves curl along the edges toward the mid-vien and resemble a rolled up scroll. The fruit of the native vine appear as single clumps at the tips of the branches, compared to fruit of the non-native vine appearing up and down the stem.
Oriental bittersweet can be reported using the Great Lakes Early Detection Network (GLEDN) App. If you haven't already downloaded this smartphone app, now is a great time to join in the early detection and reporting invasive species opportunity - we need your help!