Celastrus orbiculatus (Asiatic bittersweet)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Plant Type
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Hosts/Species Affected
- Growth Stages
- Biology and Ecology
- Soil Tolerances
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Impact Summary
- Environmental Impact
- Impact: Biodiversity
- Social Impact
- Risk and Impact Factors
- Uses List
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Celastrus orbiculatus Thunb.
Preferred Common Name
- Asiatic bittersweet
Other Scientific Names
- Celastrus articulatus Thunb.
- Celastrus orbiculata Loes.
International Common Names
- English: Asian bittersweet; Chinese bittersweet; Japanese bittersweet; oriental bittersweet
Local Common Names
- Germany: Baumwürger, Rundblättriger
- Japan: tsuru-ume-mo-doki
- New Zealand: climbing spindleberry
- USA: round-leaved bittersweet
- CELOR (Celastrus orbiculatus)
Summary of InvasivenessTop of page As a fast growing, twining vine, C. orbiculatus is a threat to other plants through constriction of the woody stems it climbs upon leading to slowed growth and eventually mechanical failure, over-topping and shading out plants beneath it, and outright competition for resources (Dreyer et al., 1987). Since its introduction to North America from eastern Asia as an ornamental vine in about 1870, C. orbiculatus has spread from sites of cultivation and naturalized extensively in the eastern half of the continent. Thanks to prolific fruit production, high seed production, rapid growth rates, wide tolerance of soils and light conditions, vegetative reproduction via rootsuckering, and its attractiveness to people, this plant is currently very widespread and expanding its territory quickly. Biologists and vegetation managers were slow to recognize the problem in part due to its similarity to the North American native C. scandens.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Celastrales
- Family: Salacia
- Genus: Celastrus
- Species: Celastrus orbiculatus
Notes on Taxonomy and NomenclatureTop of page The first written description of Celastrus orbiculatus by Thunberg in his 1784 Flora of Japan contained a printer's error that gave the specific epithet as articulatus, and this has caused over a century of confusion about the correct name of this plant (Hou, 1955). A feminine version of the specific epithet, orbiculata, was published in a 1901 description of a new form of the species (Hou, 1955) and this is the most commonly seen alternate name for the plant. Apparently, there is some debate about whether the genus name should be considered masculine or feminine. See Hou (1955) for a complete list of synonymy.
DescriptionTop of page C. orbiculatus is a deciduous woody vine that climbs by means of twining about a support. Branches are round, glabrous, light to darker brown, usually with noticeable lenticels. Axillary buds are 1-3 mm, rounded, with outer scales sometimes becoming spine-like. Leaves are glabrous, alternate in arrangement and extremely variable in size and shape, from broadly oblong-obovate to suborbicular, 2-12 cm long and 1.5-8 cm wide. Leaf margins are crenate-serrate and the leaf base is cuneate to obtuse, tip acute to rounded. Petioles are 1-3 cm long. Infloresences are axillary cymes, usually containing 3-7 flowers, sometimes terminal in male plants. Flowers are small, greenish-yellow and usually become unisexual by abortion or reduction of male or female parts, thus the plants are usually dioecious (Brizicky, 1964). Occasional vines develop both unisexual and perfect flowers and are then termed polygamo-dioecious (Gleason and Cronquist, 1991). Another reported variation is occasional monoecious plants, i.e. with both male and female flowers on the same vine (Hou, 1955). Sepals and petals are both 5. Male flowers contain 5 stamens about as long as the petals and inserted at the edge of cup-shaped disk around a vestigial pistil. Female flowers have vestigial stamens, a 3-lobed stigma, columnar style and a well developed superior ovary, sometimes imbedded in a disk (Gleason and Cronquist, 1991). Fruits are globose loculicidal capsules 6-8 mm in diameter which change in colour from green to bright yellow. Capsules are 3-valved with each locule containing 1-2 brown seeds completely enclosed in a fleshy red aril. Upon ripening, the yellow outer covering splits open to reveal the red aril, thus presenting a brightly bicoloured 'dispersal flag'. Fruit are born in clusters of 3-7 in the axils of leaves. C. orbiculatus fruit are never arranged in terminal clusters. The outer surface of roots are characteristically bright orange. The primary taxonomic reference for this section is Hou (1955). This morphological description was written by the present author for a Nature Conservancy Element Stewardship Abstract. Copyright The Nature Conservancy, used with permission.
Plant TypeTop of page Broadleaved
Vine / climber
DistributionTop of page Hou (1955) notes the native range as Japan, Korea and China, whereas USDA-ARS (2003) adds Mongolia and the Russian Far East (Primoye and Sakalin), although the abundance for C. orbiculatus is not given. C. orbiculatus is not considered harmful to the forests in Japan, i.e. not a noxious or invasive weed in its native range (Patterson, 1974). Patterson (1974) is still the best source for the area of naturalization in North America, but the work is at least 30 years out of date. It is occasionally cultivated, but presumably not naturalized, in all three Pacific coast states of the USA.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Planted||Reference||Notes|
|China||Present||Native||Hou, 1955; USDA-ARS, 2003|
|Japan||Present||Present based on regional distribution.|
|-Hokkaido||Present||Native||Not invasive||Hou, 1955; USDA-ARS, 2003|
|-Honshu||Present||Native||Not invasive||Hou, 1955; USDA-ARS, 2003|
|-Kyushu||Present||Native||Not invasive||Patterson, 1974; USDA-ARS, 2003|
|-Shikoku||Present||Native||Not invasive||Patterson, 1974; USDA-ARS, 2003|
|Korea, DPR||Present||Native||Hou, 1955; USDA-ARS, 2003|
|Korea, Republic of||Present||Native||Hou, 1955; USDA-ARS, 2003|
|Taiwan||Present||Native||Not invasive||Patterson, 1974|
|Canada||Present||Present based on regional distribution.|
|-Ontario||Restricted distribution||Introduced||Invasive||Soper and Heimburger, 1985|
|USA||Present||Present based on regional distribution.|
|-Arkansas||Restricted distribution||Introduced||Invasive||Patterson, 1974|
|-California||Present||Introduced||Not invasive||Patterson, 1974|
|-Iowa||Restricted distribution||Introduced||Invasive||Patterson, 1974|
|-Kentucky||Restricted distribution||Introduced||Invasive||Patterson, 1974|
|-Louisiana||Restricted distribution||Introduced||Invasive||Patterson, 1974|
|-Maine||Restricted distribution||Introduced||Invasive||Patterson, 1974|
|-Maryland||Restricted distribution||Introduced||Invasive||Patterson, 1974|
|-New Hampshire||Restricted distribution||Introduced||Invasive||Patterson, 1974|
|-New Jersey||Widespread||Introduced||Invasive||Patterson, 1974|
|-New York||Widespread||Introduced||Invasive||Patterson, 1974|
|-North Carolina||Widespread||Introduced||Invasive||Patterson, 1974|
|-Ohio||Restricted distribution||Introduced||Invasive||Patterson, 1974|
|-Oregon||Present||Introduced||Not invasive||Patterson, 1974|
|-Rhode Island||Widespread||Introduced||Invasive||Patterson, 1974; Dreyer, 2001|
|-South Carolina||Present||Introduced||Patterson, 1974|
|-Tennessee||Restricted distribution||Introduced||Invasive||Patterson, 1974|
|-Vermont||Restricted distribution||Introduced||Invasive||Patterson, 1974|
|-Washington||Present||Introduced||Not invasive||Patterson, 1974|
|-West Virginia||Restricted distribution||Introduced||Invasive||Patterson, 1974|
|-Wisconsin||Restricted distribution||Introduced||Invasive||Patterson, 1974|
|Russian Federation||Present||Present based on regional distribution.|
|-Russian Far East||Present||Native||Natural||USDA-ARS, 2003|
|UK||Present, few occurrences||Introduced||1891||Not invasive||Patterson, 1974|
|New Zealand||Present||Introduced||1981||Invasive||Owen, 1996|
History of Introduction and SpreadTop of page The exact date of introduction of C. orbiculatus to eastern North America is somewhat obscure, but may have been in 1860 (Rheder, 1940) or at least before 1879 (Patterson, 1974). With the abundant, attractive bi-coloured fruit and bright yellow autumn leaf colour, it quickly became a popular ornamental vine. The fruits are dispersed by birds and other wildlife as well as people, leading to its rapid spread from cultivated and naturalized sites (Dreyer et al., 1987). In the UK, the plant was cultivated in the Royal Botanic Gardens, Kew, by 1891 (Patterson, 1974) but there are no reports of C. orbiculatus naturalizing in Europe. It has been recorded as introduced into New Zealand in 1981 and is regarded as invasive there (Owen, 1996).
Risk of IntroductionTop of page C. orbiculatus is widely available from nurseries and mail order companies as an ornamental species and as such further spread is likely.
HabitatTop of page C. orbiculatus is common and widely distributed on lowland slopes or in thickets at altitudes of 100-1400 m in its native range (Hou, 1955). Patterson (1974) notes habitats as on lowland or upland pastures, under the canopy of little-light secondary forests, and as a hedge plant not forming dense tangled thickets. Where introduced in the USA, it is most abundant on roadsides, open, recently disturbed, mesic sites, and the edges between fields, thickets and forests.
Habitat ListTop of page
|Coastal areas||Present, no further details||Harmful (pest or invasive)|
|Cultivated / agricultural land||Present, no further details||Harmful (pest or invasive)|
|Disturbed areas||Present, no further details||Harmful (pest or invasive)|
|Managed forests, plantations and orchards||Present, no further details||Harmful (pest or invasive)|
|Managed grasslands (grazing systems)||Present, no further details||Harmful (pest or invasive)|
|Rail / roadsides||Present, no further details||Harmful (pest or invasive)|
|Urban / peri-urban areas||Present, no further details||Harmful (pest or invasive)|
|Natural forests||Present, no further details||Harmful (pest or invasive)|
|Natural grasslands||Present, no further details||Harmful (pest or invasive)|
|Riverbanks||Present, no further details||Harmful (pest or invasive)|
Hosts/Species AffectedTop of page C. orbiculatus is not generally a weed of agriculture but is an invasive plant threatening commercial forestry and pastures. For example, in the USA, invasions of C. orbiculatus are noted as a threat to hardwood silviculture in the Appalachians (McNab, 1987) and it invades abandoned pasture in Connecticut (Fike and Niering, 1999).
Growth StagesTop of page Flowering stage, Fruiting stage, Seedling stage, Vegetative growing stage
Biology and EcologyTop of page Genetics
The chromosome number is n=23 (Bowden, 1945). Artificial hybridization with the North American native C. scandens has been documented twice. When White and Bowden (1947) crossed the species, the resulting offspring were few in number and less vigorous than either parent. Pooler et al. (2002) crossed C. scandens (female parent) with C. orbiculatus and found classic hybrid vigour; the resulting plants had less seed dormancy and were more vigorous than progeny of C. scandens alone. Dreyer et al. (1987) found much higher pollen and seed viability in C. orbiculatus compared to C. scandens. Given the decline in C. scandens populations and the concurrent rise in C. orbiculatus populations, the possibility of introgressive hybridization has been speculated (Dreyer et al., 1987; Pooler et al., 2002; Steward et al., 2003). Plants apparently intermediate between these two species have occasionally been noted in the field (Dreyer et al., 1987) but not in great numbers.
Physiology and Phenology
Flowers bloom in late May to early June in Connecticut, USA, and fruit ripen in September and remain on the vine through much of the winter. Leaves are fully expanded by late May, begin to yellow in mid-September and fall by mid to late October. For a detailed study of photosynthesis and water relations in C. orbiculatus refer to Clement et al. (1991).
Plants are usually dioecious (Brizicky, 1964) and occasionally monoecious, i.e. with both male and female flowers on the same vine (Hou, 1955) or polygamo-dioecious, i.e. with both unisexual and perfect flowers on the same plant (Gleason and Cronquist, 1991). Brizicky (1964) notes Hymenopterous insects, especially bees, are its main pollinators, and Wyman (1950) also found wind pollination to be effective. Fruit dispersal is generally thought to be by birds and small mammals (Wheeler, 1987). Seeds require cold stratification for germination. Patterson (1974) found germination percentages of 30-95% with highest germination under low light intensities. Dreyer et al. (1987) found an average of 71% germination with seed collected in Connecticut, USA and confirmed higher germination at lower light levels. In a 3-year seed bank persistence study of native and non-native congeneric plants, Van Clef and Stiles (2001) found that both C. scandens and C. orbiculatus had negligible germination after the first year. C. orbiculatus produces root suckers prolifically, and thus a single individual can expand to a dense thicket in a relatively short time. Small pieces of root left during clearing operations resprout quickly to form new plants.
C. orbiculatus germinates well in low light conditions found beneath existing plant cover. Fastest growth is attained in high light locations, with plants suppressed by shade ready to take advantage of canopy gaps caused by wind or other disturbance events. At a forest site in the Appalachian Mountains of North Carolina, USA (McNab and Loftis, 2002) presence of the vine was associated with mesic soil conditions, overstorey canopy gaps, locations with past timber harvests, and forest floor scarification. In Massachusetts, USA, Silveri et al. (2001) found optimal growth in moist soil under high irradiance, and in a forest disturbed 14 years previously by logging, C. orbiculatus invaded 2 years after the harvest and the vines were more abundant on the former logging roads than the surrounding logged area. Sinclair et al. (1987) list this plant as intolerant of flooding or waterlogged soils.
A number of birds, including black-capped chickadees, the northern mockingbird, European starling and blue jay all feed on C. orbiculatus fruit during the winter in the USA.
Soil TolerancesTop of page
Special soil tolerances
Notes on Natural EnemiesTop of page No natural enemies have been reported in the literature where introduced, though studies may exist in its native range.
Means of Movement and DispersalTop of page Birds, small mammals and other wildlife are attracted to the multicoloured fruit and are a primary means of dispersal. Commercial plant nurseries are still propagating and selling this plant and this is the principal means of long-distance dispersal. In the USA, plants are bought from nurseries and mail order companies, that often mistakenly represent it as the native North American species, C. scandens. People also collect and dry fruiting stems for decorative purposes, moving the seeds to new locations where the material is later discarded. In addition to seeds, pieces of root, moved in soil for landfill and other purposes, can also spread the plant to new locations.
Impact SummaryTop of page
|Fisheries / aquaculture||None|
ImpactTop of page Economic impacts have not been documented. Given that awareness of the problem is increasing, infestations are extensive in many locations, and removal is very labour intensive, increasing costs can be expected.
Environmental ImpactTop of page Competition, to the point of complete suppression and exclusion of native species is a major impact (Patterson, 1974; Dreyer et al., 1987; Fike and Niering, 1999), though there are no reports of specific effects on environmental processes.
Impact: BiodiversityTop of page Competition, to the point of complete suppression and exclusion of native species is a major impact (Patterson, 1974; Dreyer et al., 1987; Fike and Niering, 1999). This leads to a loss of biodiversity. There appears to be less C. scandens in the USA than before the introduction of C. orbiculatus (Dreyer et al., 1987; Steward et al., 2003), and the possibility of introgressive hybridization eliminating the native C. scandens is a possible threat to biodiversity.
Social ImpactTop of page Although an attractive plant, it is so invasive that it negatively affects the aesthetics and usefulness of cultivated and natural landscapes.
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Highly adaptable to different environments
- Highly mobile locally
- Has high reproductive potential
- Negatively impacts agriculture
- Negatively impacts tourism
- Reduced amenity values
- Reduced native biodiversity
- Competition - monopolizing resources
- Difficult/costly to control
UsesTop of page C. orbiculatus is intentionally grown as an ornamental vine in the USA, Asia, the UK and probably elsewhere in Europe. It is an attractive vine that gardeners and landscapers still purchase and utilize. It is also used as a hedging plant and well as for urban amenity planting.
Uses ListTop of page
Similarities to Other Species/ConditionsTop of page In North America, the introduced C. orbiculatus and the native C. scandens are often confused. C. orbiculatus can be reliably distinguished from the native C. scandens only by the location of female flowers and fruit. These are uniformly axillary cymes in C. orbiculatus and terminal panicles of numerous flowers or fruit in C. scandens. A second difference is the yellow colour of the outer fruit covering in C. orbiculatus compared to the orange colour of C. scandens outer fruit cover. The colour of the inner aril is red in both species. Identification by leaf shape or size, or by male inflorescence type, is not reliable. Reasonably good illustrations showing the differences between the two species can be found in Gleason (1952), Holmgren (1998) and McNab and Meeker (1987).
Prevention and ControlTop of page Cultural Control
Goats and sheep have been observed to effectively control C. orbiculatus infestations in the USA.
Repeated cutting or mowing, where possible and appropriate, will suppress and eventually eliminate C. orbiculatus. In Connecticut, USA this must be more often than monthly during the growing season.
Dreyer (1988) reported that the use of herbicides was successful for controlling dense, low patches of C. orbiculatus. Vegetation in the entire area is cut to the ground early in the growing season and allowed to regrow, and approximately one month later, foliar applications of a triclopyr ester or salt applied by backpack sprayer results in a 100% rootkill of C. orbiculatus. No off-target damage or root uptake by adjacent plants has been noted in many years of using this technique. The same study found foliar applications of glyphosate and amitrole were both ineffective in killing the roots of C. orbiculatus. Hutchison (1992) reports that foliar applications of a mixture of 2,4-D and triclopyr to C. orbiculatus will effectively reduce the population when applied in mid to late October. Ahrens (1987) noted complete control with tripclopyr ester and imazapyr, and partial control with glyphosate. Dreyer (2001) modified the mow and spray technique previously mentioned for use on larger areas with tractor-mounted agricultural equipment to test for the minimum effective dose of triclopyr, and the effect of spray date. Late growing season (early September) applications as low as 0.5% triclopyr in water effectively killed C. orbiculatus, whereas early summer applications of 1% triclopyr provided significant, but not complete, rootkill. An additional advantage to using triclopyr is that, unlike the commonly used glyphosate, it does not kill monocotyledonous plants and, when present, these plants will remain to prevent soils from being completely denuded and potentially eroded. Work is currently underway in Connecticut, USA to test the effectiveness of treating large cut stems of C. orbiculatus with herbicides.
No biological control of C. orbiculatus has been recorded.
Control of C. orbiculatus along roadsides would go a long way toward decreasing the seed source. In heavy infestations on fields and shrublands, an initial herbicide treatment to rootkill existing plants followed by periodic controlled burning (Niering and Dreyer, 1989) or periodic selective re-spraying should prevent re-establishment by seed.
ReferencesTop of page
Aherns J, 1987. Herbicides for Control of Oriental Bittersweet. Proceedings of the Northeastern Weed Science Society, 41:167-170.
Brizicky G, 1964. The genera of Celastrales in the Southeastern United States. Journal of the Arnold Arboretum, 45:206-218.
Clement C; Warren R; Dreyer G; Barnes P, 1991. Photosynthesis, water relations and fecundity in the woody vines American and Oriental bittersweet (Celastrus scandens and C. orbiculatus). Annual Meeting Bot. Soc. Amer. Poster Abstract in American Journal of Botany, 78(6):134-135.
Dreyer G, 2001. Oriental Bittersweet Control Project, Sachuest Point National Wildlife Refuge. Unpublished Final Report. Produced under contract to the US Fish and Wildlife Service.
Dreyer G; Baird L; Fickler C, 1987. Celastrus scandens and Celastrus orbiculatus: Comparisons of reproductive potential between a native and an introduced woody vine. Bull. Torrey Bot. Club 114(3):260-264.
Dreyer GD, 1988. Efficacy of triclopyr in rootkilling oriental bittersweet (Celastrus orbiculatus Thunb.) and certain other woody weeds. Proceedings, 42nd annual meeting of the Northeastern Weed Science Society, 120-121
Fike J; Niering WA, 1999. Four decades of old field vegetation development and the role of Celastrus orbiculatus in the northeastern United States. Journal of Vegetation Science, 10(4):483-492; 2 pp. of ref.
Gleason H, 1952. The New Britton and Brown Illustrated Flora of the Northeastern United States and Adjacent Canada, Volume 2. New York, USA: The New York Botanical Garden and Hafner Press.
Gleason HA; Cronquist A, 1991. Manual of Vascular Plants of Northeastern United States and adjacent Canada. Second edition. New York, USA: The New York Botanical Garden.
Holmgren N, 1988. The Illustrated Companion to Gleason and Cronquist's Manual. Illustrations of the Vascular Plants of Northeastern United States and Adjacent Canada. Bronx, NY, USA: The New York Botanical Garden.
Hou D, 1955. A revision of the genus Celastrus. Annals of the Missouri Botanical Garde,n 42:215-302.
McNab WH; Loftis DL, 2002. Probability of occurrence and habitat features for oriental bittersweet in an oak forest in the southern Appalachian mountains, USA. Forest Ecology and Management, 155(1/3):45-54; 27 ref.
Niering W; Dreyer G, 1989. Effects of prescribed burning on Andropogon scoparius in postagricultural grasslands in Connecticut. American Midland Naturalist, 122:88-102.
Owen SJ, 1996. Ecological weeds on conservation land in New Zealand: A database. Department of Conservation, Wellington, New Zealand: DOC Science Publications. http://www.hear.org/weedlists/other_areas/nz/nzecoweeds.htm.
Pooler MR; Dix RL; Feely J, 2002. Interspecific hybridizations between the native bittersweet, Celastrus scandens, and the introduced invasive species, C. orbiculatus. Southeastern Naturalist, 1(1):69-76; 17 ref.
Rheder A, 1940. Manual of Cultivated Trees and Shrubs. Second Edition. New York, USA: MacMillan Publishing Co., Inc.
Scoggan HJ, 1978. The flora of Canada, Part 3 - Dicotyledoneae (Saururaceae to Violaceae). Ottawa, Quebec, Canada: National Museum of Natural Sciences, National Museums of Canada, 568 pp.
Silveri A; Dunwiddie P; Michaels H, 2001. Logging and edaphic factors in the invasion of an Asian woody vine in a mesic North American forest. Biological Invasions, 3:379-389.
Sinclair W; Lyon H; Johnson W, 1987. Diseases of Trees and Shrubs. Ithaca, NY, USA: Cornell University Press.
Soper J; Heimburger M, 1985. Shrubs of Ontario. Life Sciences Miscellaneous Publications. Second revised printing. Toronto, Ontario, Canada: The Royal Ontario Museum.
Steward A., Clemants S, Moore G, 2003. The concurrent decline of the native Celastrus scandens and spread of the non-native Celastrus orbiculatus in the New York Metropolitan area. Journal of the Torrey Botanical Society, 130 (2): 143-146.
USDA-ARS, 2003. Germplasm Resources Information Network (GRIN). Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch.aspx
Van Clef M; Stiles E, 2001. Seed longevity in three pairs of native and non-native congeners: assessing invasive potential. Northeastern Naturalist, 8(3):301-310.
Wheeler L, 1987. Oriental bittersweet: avian dispersal in winter in relation to other species of fruiting plants. Undergraduate Individual Study Report. Zoology Department, Connecticut College, New London, USA.
White O; Bowden W, 1947. Oriental and American bittersweet hybrids. Journal of Heredity, 38(4):125-127.
Wyman D, 1950. Fruiting habits of certain ornamental plants. Arnoldia, 10(13):81-85.
Distribution MapsTop of page
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