From Wreath to Forest

Contact: Sylvan Kaufman, Adkins Arboretum | 410-634-2847 (ext. 13)

Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

ANNAPOLIS, MD (Dec. 2, 2003) – The colors of fall are reflected beautifully in the yellow and red fruits of the Oriental bittersweet vine decorating wreaths or dried flower arrangements, but what happens when the colors fade and that bittersweet is thrown out into the woods or on to a compost pile? Oriental bittersweet now festoons trees and trails over the ground from Maine to Louisiana, earning it the nickname, "Kudzu of the North". The Maryland Invasive Species Council (MISC) has chosen Oriental bittersweet as December's "Invader of the Month."

Oriental bittersweet, Celastrus orbiculatus, is native to eastern Asia, including Korea, China and Japan. It was introduced to the United States as early as 1736 as an ornamental plant. It is a woody vine with rounded leaves that produces inconspicuous clusters of small yellowish flowers in spring. Flowers and fruits occur where the leaves meet the stems. Birds and small mammals eat and disperse the fruits.

Oriental bittersweet can cover tall trees causing them to weaken and collapse under the weight of the vines. The stems twine around the trunks, and as they thicken they can cut into the bark and girdle the tree. Any small plants at ground level are cut off from light by the vines growing over them, but oriental bittersweet seeds germinate best in shade.

A more subtle influence of the Oriental bittersweet invasion is its potential effect on the American bittersweet, Celastrus scandens. The very similar looking American bittersweet produces flowers and fruits only at the tips of the stems rather than along the stems. American bittersweet is not aggressive and may be displaced by Oriental bittersweet. The Oriental bittersweet may also hybridize with American bittersweet, introducing its genes into the native populations and making it even more difficult to find actual American bittersweet.

Instead of using Oriental bittersweet in your fall decorations, try orange strawflowers or red holly berries, dark inkberry fruits, or the beautiful dusty blue berries of red cedar. If you want to plant an ornamental vine in place of Oriental bittersweet, try trumpet honeysuckle (Lonicera sempervirens) with beautiful coral colored flowers and orange-red fruits, American wisteria (Wisteria frutescens) with fragrant purple flowers and long seed pods, or crossvine (Bignonia capreolata) with trumpet-shaped orange-yellow flowers. If nothing but bittersweet will do, try the plastic variety sold at craft stores or be sure and discard your bittersweet in a landfill or incinerator.

For more information on this and other invasive species in Maryland, visit the Maryland Invasive Species Council.