Introduced Species Summary Project
Oriental Bittersweet (Celastrus orbiculatus)
Scientific Name: Celastrus orbiculatus
Phylum or Division:
Identification: Oriental bittersweet is a deciduous, twining and climbing woody vine. It entwines its round, brown stems about other plants and structures, climbing as high as sixty feet, forming thicket and arbor infestations. It has elliptic to rounded leaves, with dangling clusters of inconspicuous yellowish flowers producing green/yellow fruits which split in Autumn to reveal showy bright red seeds.
Oriental bittersweet is similar in appearance to American bittersweet and verification of identification is critical. One way to clearly distinguish between the two is by locating the female flowers and fruit of the plants. On Oriental bittersweet the flowers lay in clusters of three to seven, near where the stem attaches to the branch of the plant. In C. scandens, the now scarce native plant, they form in terminal clusters composed of multiple stalks, revealing numerous flowers or fruits. A less reliable difference is the color of the outer covering of the fruit. The fruit of Oriental bittersweet is yellow while American bittersweet fruit is orange.
Original Distribution: Native to
Current Distribution: Naturalized in
Mode(s) of Introduction: Introduced for ornamental purposes, subsequently escaped from cultivation. Note: While sales are prohibited in many states, it is still commercially grown and sold in others, often mislabeled as “American Bittersweet.” As a result, continued introduction in new locations is likely (see below).
Reason(s) Why it has Become Established: The vine is highly attractive as an ornamental and easy to grow and propagate. It was formerly planted extensively in highway landscaping and for wildlife food and cover and erosion control. The viable fruits continue to be sold for dried flower arrangements and are frequently disposed of on compost and brush piles, where they can readily be spread by birds and small mammals.
Once dispersed, habitat
preferences are wide and include open woods, thickets, roadsides and fence
rows. In contrast to the tropics, lianas
(vines) are relatively uncommon in the northern temperate areas. The existence of a significant ecological
niche in the temperate zone for lianas may account for the success of invasive
species such as Pueraria
Ecological Role: Considered an important winter food for birds, comparable in lipid and sugar content to the fruit of other species. Black-capped Chickadees, Northern Mockingbirds, European Starlings and Blue Jays feed on C. orbiculatus during the winter months.
Hybridization with the native species C. scandens is possible, with loss of genetic identity. This is cited as a possible reason for the decline in distribution of the native in recent years. Other researchers, however, claim that the hybrid is weak and not commonly observed in natural settings.
Benefit(s): In addition to their commercial value as
ornamentals, plant extracts of the Celastraceae have been used for centuries
Threat(s): C. orbiculatus poses a serious threat to individual plants and plant communities due to its high reproductive rate, long range dispersal, and rapid growth rates. Individual plants can be severely damaged and even killed by the aggressive twining and climbing growth habits of this vine. All types of plants, and even entire plant communities, can be over-topped and shaded by the vine's rapid vegetative growth.
Direct competition between C. orbiculatus and C. scandens has been hypothesized as a cause for the decline of the native species. However, loss of suitable habitat may be the underlying reason for its decline, as the habitat preferred by the native (open landscape) has been declining due to forest regeneration and forest fire suppression.
Level Diagnosis: Medium Priority. C.
orbiculatus is still expanding its range in the Northeast and westward
Control Method: Manual, mechanical and chemical control methods are all effective; employing a combination of methods often yields the best results and may reduce potential impacts to native plants, animals and people. Low-growing populations have been successfully treated by cutting and applying triclopyr herbicide to the regrowth about a month later. Larger vines may be cut and the stump treated immediately with triclopyr herbicide. For large infestations spanning extensive areas of ground, a foliar herbicide may be the best choice rather than manual or mechanical means which could result in soil disturbance.
Recovery of natural areas highly infested with C. orbiculatus is unpredictable. Even with complete removal and root kill of C. orbiculatus, substantial seedling regeneration occurs in following years, probably due to a persistent soil seed bank. In cases where all nearby seed sources cannot be eliminated, reinfestation is a continual possibility.
biological controls are currently available for this plant.
Photograph: Allison, James R., Georgia Department of Natural Resources, www.invasive.org
Comparative Ecology of an Invasive Bittersweet Species (Celastrus orbiculatus) and its Native Congener (C. scandens),” Leicht,
Stacey Anne (Ph.D. Thesis,
“Interspecific Hybridizations between the Native Bittersweet, Celastrus Scandens, And The Introduced Invasive Species, C. Orbiculatus,” Pooler, Margaret R., Dix, Ruth L., Feely, Joan (Southeastern Naturalist, Volume 1, Issue 1 (March 2002), pp. 69–76)
Invasive Exotic Weeds (http://www.invasive.org/weeds.cfm)
ITIS Standard Report Page Celastrus orbiculatus (http://www.itis.usda.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=506068)
Oriental Bittersweet – Nonnative Invasive Plants of Southern Forests (http://www.invasive.org/eastern/srs/OAB.html)
GRIN-NPGS Taxonomy Information (http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?9719)
Oriental Bittersweet – Southeast Exotic Pest Plant Council Invasive Plant Manual (http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?9719)
Element Stewardship Abstract for C. orbiculata (http://tncweeds.ucdavis.edu/esadocs/documnts/celaorb.html)
USDA PLANTS Profile for Celastrus orbiculatus (Oriental bittersweet (http://plants.usda.gov/java/nameSearch?keywordquery=Celastrus+orbiculatus&mode=sciname&submit.x=15&submit.y=9)
Oriental Bittersweet: A Patient Invader (http://www.srs.fs.usda.gov/newsroom/newsrelease/2004/nr_2004-06-24-bittersweet.htm)
Author: Jennifer L. Costley
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