Oriental bittersweet (Celastrus orbiculatus)

Oriental bittersweet twining with fruits present (c) Elizabeth J. Czarapata

Description

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 generally more rounded with finely toothed margins, 2 to 5 inches long, and 1 to 3.5 inches wide, though they may be oblong with pointed tips. 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.

Look-alikes

This species can be confused with, and is sometimes sold labeled as the native American bittersweet (Celastrus scandens). However, the American bittersweet’s flowers and fruit clusters grow only at the end of each stem, with fruits that have orange capsules and are larger. Leaves are usually more pointed and elliptical, sometimes twice as long as wide. The species are known to hybridize, which is why it is important to correctly identify plants before purchasing, as American bittersweet is becoming less common.

American bittersweet fruits are in clusters at the end of branches and have an orange capsule; photo by Courtney LeClair, WI DNR	American bittersweet fruits are in clusters at the end of branches; photo by Courtney LeClair, WI DNR
Oriental bittersweet fruits; photo by Courtney LeClair, WI DNR	Oriental bittersweet capsule revealing fruit; photo by Courtney LeClair, WI DNR

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 where seeds can easily germinate. Reproduction also occurs through vegetative root suckering.

Oriental bittersweet twining (c) James H. Miller, USDA Forest Service, Bugwood.com

Control

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. Extensive infestations can also be treated 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.

Additional Information (Links exit DNR)

UW-Madison Herbarium
USGS
Plant Conservation Alliance
Element stewardship abstract for Asiatic Bittersweet