Plant Invaders of Mid-Atlantic Natural Areas

Swearingen, J., K. Reshetiloff, B. Slattery, and S. Zwicker. 2002. Plant Invaders of
Mid-Atlantic Natural Areas. National Park Service and U.S. Fish & Wildlife Service, 82 pp.

James H. Miller

James H. Miller

Origin: Eastern Asia, Korea, China and Japan

Background
Oriental bittersweet was introduced into the United States in the 1860s as an ornamental plant and it is still widely sold for landscaping despite its invasive qualities. It is often associated with old home sites, from which it has escaped into surrounding natural areas.

Distribution and Ecological Threat
Oriental bittersweet occurs from New York to North Carolina, westward to Illinois. It infests forest edges, open woodlands, fields, hedgerows, coastal areas, salt marsh edges and particularly disturbed lands. While often found in more open, sunny sites, its shade tolerance allows it to invade forested areas. Oriental bittersweet is an aggressive invader that threatens vegetation at all heights in forested and open areas. It grows over other vegetation, completely covering and killing other plants by preventing photosynthesis, by girdling, and by uprooting trees through excessive weight. In the Northeast, Oriental bittersweet appears to be displacing the native climbing bittersweet, Celastrus scandens, through competition and hybridization.

James H. Miller

Description and Biology

• Plant: a deciduous, woody, twining vine in the staff-tree family (Celastraceae), which sometimes occurs as a trailing shrub. Stems of older plants sometimes grow to four inches in diameter.
• Leaves: glossy, rounded, finely toothed and arranged alternately along the stem.
• Flowers, fruits and seeds: abundant clusters of small greenish flowers emerge from most leaf axils; globular, green to yellow fruits split open at maturity to reveal three red-orange, fleshy arils that surround the seeds; seeds germinate in late spring.
• Spreads: Oriental bittersweet spreads by seed, which is dispersed to new areas by many species of birds. People also spread seed widely when using the plant for wreaths and ornamental arrangements. It also expands vegetatively by stolons and rhizomes, and through root suckering (the ability to send shoots up from the roots).
• Look-alikes: This plant is easily confused with our native climbing bittersweet vine (Celastrus scandens), which flowers at the stem tips rather in the leaf axils, it is imperative that correct identification be made before controls are attempted.

Prevention and Control
Manual, mechanical and chemical methods can be employed to control bittersweet. Vines can be pulled out by the roots, cut repeatedly or treated with systemic herbicides. No biological controls are currently known for oriental bittersweet.

Native Alternatives
Note: Although our native bittersweet (Celastrus scandens) is an excellent alternative plant to use, many nurseries confuse it with the exotic invasive Oriental bittersweet. Be certain of the species you are buying or choose another plant. Other options include:

passionflower (Passiflora incarnata) R. Harrison Wiegand	trumpet creeper (Campsis radicans) Britt Slattery, USFWS
pipevine (Aristolochia macrophylla) R. Harrison Wiegand	trumpet honeysuckle (Lonicera sempervirens) Britt Slattery, USFWS

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