Oriental bittersweet (also known as round-leaved or Asiatic bittersweet) is a perennial, deciduous, woody climbing vine. Younger leaves are oblong, but mature leaves are more rounded with finely toothed margins, 2 to 5 inches long, and 1 to 3.5 inches wide. The stems are brown to gray, often have raised lenticels, and can grow up to 4 inches wide and 60 feet high. The small flowers have 5 greenish-yellow petals and produce clusters of 2-4 fruits along the length of the stem at the leaf axils. The fruit’s yellow outer membrane eventually reveals a red inner-fruit.
This species can be easily confused with the native American bittersweet (Celastrus scandens). However, the American bittersweet’s flowers and fruit clusters grow only at the end of each stem, and the leaves are usually more pointed and elliptical, sometimes twice as long as wide. The species are known to hybridize.
Impacts & Habitat
Oriental bittersweet is found in grasslands, woodland edges, forests, roadsides, and beaches. It grows quickly and can overtop native plants and tall trees, shading, girdling, and eventually downing them. The seeds germinate best in low-light environments, and under appropriate light and moisture regimes, the vine may grow in nearly pure stands. The seeds are easily dispersed, and are commonly spread when birds eat the fruit or people dispose of craft or floral arrangements in compost and brush heaps. Reproduction also occurs through vegetative root suckering.
The most effective treatment, especially around native plants and for vines in the canopy, is treating cut stems with triclopyr and a non-toxic bark-penetrating oil, or glyphosate. Seedlings and small infestations can also be hand-pulled or dug out by the roots before the fruits ripen. Treat extensive infestations with foliar herbicides after the first hard frost in the fall or in the spring when most native plants are dormant. Monitor all sites for regrowth.