Introduced Species Summary Project
Oriental
Bittersweet (Celastrus orbiculatus)
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Common Name: Oriental Bittersweet, (Japanese
Bittersweet, Asian bittersweet, Asiatic bittersweet. In
Scientific Name: Celastrus orbiculatus
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Classification:
Phylum or Division:
Magnoliophyta
Class: Magnoliopsida
Subclass: Rosidae
Order: Celastrales
Family: Celastraceae
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
Site and Date of Introduction: The exact date of introduction to eastern
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
throughout
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.
Control
Level Diagnosis: Medium Priority. C.
orbiculatus is still expanding its range in the Northeast and westward
across the
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.
No
biological controls are currently available for this plant.
Photograph: Allison, James R., Georgia
Department of Natural Resources, www.invasive.org
References:
“The
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
Last Edited:
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