Tuesday, December 14, 2010

Noxious Oriental Bittersweet

First your eyes are drawn to the attractive yellow capsules enclosing striking red fleshy fruits. Then you notice the berried vine climbing high into the tree canopy or draping over a shrub... maybe even flowing over an arbor or fence. You think to yourself, “ What a striking plant! What is it and where can I get one?”

Thus the siren song of Bittersweet begins. The plant just described is Oriental Bittersweet, Celastrus orbiculatus, and is one of the most aggressive and serious invasive, exotic plants in our area. A twining, climbing vine, Oriental Bittersweet can drape and climb over other desirable shrubs and trees, eventually shading out other plants and girdling the unlucky plants that support the vine.

Enormous root systems, robust annual growth, and numerous seedlings allow the vine to spread throughout forest and urban landscapes. The seeds are also consumed by birds and other animals and are then scattered wherever they are deposited. In western North Carolina, Bittersweet vines are commonly made into decorative wreaths, which are sold to unsuspecting buyers. When the vines are discarded, whether in the compost pile or thrown out in the woods, the cycle begins anew and Bittersweet claims new real estate.

Native plant enthusiasts will point out that there is a native American Bittersweet, Celastus scandens, which is nowhere near as aggressive or threatening as its exotic cousin. However, there is documented evidence that the two species can hybridize, leading to more aggressive tendencies of the resulting hybrid vine. The main difference between American Bittersweet and Oriental Bittersweet is the location of the flowers (and thus, later on the berries). American Bittersweet bears terminal flowers at the tips of the branches, while Oriental Bittersweet bears axillary flowers all along the vine. American Bittersweet seed capsules are orangish-yellow and lack the two-toned coloration.

Oriental Bittersweet
Strangely enough, Oriental Bittersweet is still noted as an ornamental species by some sources despite its reputation as an ecological menace. It is listed as a noxious, invasive weed in North Carolina.

While wintertime is not the recommended time of year for eradication efforts of Oriental Bittersweet, it is the perfect time for easily identifying where the vine persists. Flagging tape or selective markings with spray paint can label the plant now so that control efforts can be made during the following growing season. The USDA publication Nonnative Invasive Plants of Southern Forests has information on controlling Oriental Bittersweet as well as other devastating invasive plants.

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