Celastrus orbiculatus Thunb.

Celastrus orbiculatus Thunb.
Asian Bittersweet, Oriental Bittersweet

Threat Level	Category
Established	Vine

Similar Species May be confused with the following native and/or non-native species. Landscape Alternatives lists native horticultural substitutes	Celastrus scandens

Description

Height

Oriental bittersweet is a deciduous woody vine that may become a spreading, trailing shrub. Maximum height can reach 60 feet (19 m) depending on surrounding vegetation. Vines grow up to 4 inches (10 cm) in diameter.

Stem

Stems and branches are round, glabrous, drab olive or light to dark brown with many discernible raised whitish corky lenticels. Branch scars of fruit clusters are semicircular, each with a tiny corky shelf projection. Twining and arbor forming with many alternate drooping branches growing at angles.

Leaves

Leaves are alternate and are variable in size 1.2-5 inches (3-12 cm) and shape from oblong-obovate to suborbicular. They have long tapering tips when young, becoming larger and round tipped when mature. Margins are finely blunt toothed and base tapers to a petiole 0.4-1.2 inches (1-3 cm) long. Leaves are dark green and turn bright yellow in late summer and fall.

Flowers

Inflorescence is a few-flowered (3-7) cyme in the axils of leaves. Flowers have 5 sepals and 5 petals, and are greenish-yellow in color. Varieties can be dioecious (separate plants for male and female flowers) or monecious (male and female flowers on same plant). Blooms in May.

Fruit

Dangling clusters of spherical 0.5 inch (1.2 cm) capsules with a persistent pistil start out green changing to bright yellow upon maturity. Capsule splits open and folds upward revealing a round, scarlet, three-valved fruit, with each section containing one to three white seeds. Matures August-September and is persistent in winter.

Images

Photo: James R. Allison, Georgia Department of Natural Resources, Bugwood.org
More images of Celastrus orbiculatus

Life History

Oriental bittersweet, in the Celastraceae or Staff-Tree Family, is a serious threat to plant communities due to its high reproductive rate, long range dispersal, ability to root sucker, and rapid growth rate. Climbing Oriental bittersweet vines severely damages native vegetation by constricting and girdling stems. Vines can shade, suppress, and ultimately kill native vegetation. Oriental bittersweet has been shown to hybridize with the relatively rare American bittersweet (Celastrus scandens L.). Hybridization may lead to the loss of American bittersweet's genetic identity through introgression. Both are members of the Celastraceae (Stafftree) family.

Oriental bittersweet flowers in May in Tennessee. Hymenopterous insects, especially bees, are the primary pollinators, but wind pollination is also successful. Fruit ripens in August through September and remains on the stem into the winter. Seed dispersal is by birds or small mammals. Seedling germination is generally high (up to 95%) and begins in mid to late spring. The highest rate of seed germination is in lower light intensities. Seedlings increase photosynthesis two-fold when exposed to direct sunlight. The plants develop and expand by layering stolons and root suckers. Annual growth rate is from 1-12 feet (0.3-3.0 m) with little additional growth after about seven years. The vine has been traditionally collected as home decorations in winter for the showy fruit.

Habitat

Oriental bittersweet has a wide range of habitat preferences including roadsides, old homesites, thickets, and alluvial woods. Oriental bittersweet is shade tolerant, readily germinating and growing under a closed forest canopy. Found as scattered plants to extensive infestations in forest openings, margins, and roadsides as well as in meados.

Origin and Distribution

Oriental bittersweet is native to Japan, Korea, and northern China. It was introduced into the U.S. in 1860. Naturalized plants were first collected in Connecticut in 1916. Oriental bittersweet has become naturalized in 21 of 33 states in which it is cultivated. Present distribution is throughout the northeastern and southeastern U.S. extending to the southeastern Great Plains. Other states where it is deemed invasive: CT, DC, DE, IL, IN, KY, MA, MD, ME, MI, MO, NC, NH, NJ, NY, PA, RI, VA, VT, WI, WV. Federal or state listed as noxious weed, prohibited, invasive or banned: CT, MA, NH, NC, VT


Sources: Information on this plant page derived primarily from the Tennessee Management Manual and James H. Miller's Nonnative Invasive Plants of Southern Forests, USDA Forest Service.

Management Recommendations

Management Recommendations

Since Oriental bittersweet produces numerous seeds, extensive seed reserves canbecome established in the soil within a year or two. Seeds of Oriental bittersweet remain viable for several years and control actions must continue until seed sources are eliminated.

Mechanical Control

Cutting: Cut climbing or trailing vines as close to the root collar as possible. This technique is feasible on small populations; as a pretreatment on large impenetrable sites; in areas where herbicide cannot be used; or if labor resources are not sufficient to ade-quately implement herbicidal control. This treatment will prevent seed production and strangulation of surrounding woody vegetation. Oriental bittersweet will resprout unless cut so frequently that its root stores are exhausted. Treatment should begin early in the growing season and be repeated at two-week intervals until autumn.

Grubbing: This method is appropriate for small initial populations or environmentally sensitive areas where herbicides cannot be used. Using a pulaski or similar digging tool, remove the entire plant, including all roots and runners. Juvenile plants can be hand pulled depending on soil conditions and root development. Any portions of the root system not removed will potentially resprout. All plant parts, including mature fruit, should be bagged and disposed of in a trash dumpster to prevent reestablishment.

Herbicidal Control

Stump Treatment

Use this method in areas where vines are established within or around non-target plants, or where vines have grown into the canopy.

Glyphosate: Cut the stem 5 cm (2 in) above ground level. Immediately apply a 25% solution of glyphosate and water to the cross-section of the stem. This procedure is effective at temperatures (as low as 40°F) and may require a subsequent foliar application of glyphosate.

Triclopyr: Cut the stem 5 cm (2 in) above ground level. Immediately apply a 25% solution of triclopyr and water to the cross-section of the stem This procedure remains effective at low temperatures (<60°F) as long as the ground is not frozen. A subsequent foliar application may be necessary to control new seedlings.

Basal Bark Method

Apply triclopyr as a 20% solution in commercially available basal oil, diesel fuel, or kerosene (2.5 quarts per 3-gallon mix) with a penetrant (check with herbicide distributor) to the lower 16 inches of stems.

Foliar Spray Method

Use this method to control large populations July to October. It may be necessary to precede foliar applications with stump treatments to reduce the risk of damaging non-target species.

Glyphosate: Apply a 2% solution of glyphosate and water plus 0.5% non-ionic surfactant to thoroughly wet all foliage. Do not apply so heavily that herbicide will drip off leaves. Glyphosate is a non-selective systemic herbicide that may kill non-target partially sprayed plants. Ambient air temperature should be above 65°F.

Triclopyr: Apply a 2% solution of triclopyr and water to thoroughly wet all foliage. Do not apply so heavily that herbicide will drip off leaves. The ideal time to spray is after surrounding native vegetation has become dormant (October-November) to avoid affecting non-target species. A 0.5% concentration of a non-ionic surfactant is recommended in order to penetrate leaf cuticle. Ambient air temperature should be above 65°F.