Celastrus orbiculata - Thunb.
Oriental Bittersweet
Other English Common Names: Asian Bittersweet
Other Common Names: oriental bittersweet
Taxonomic Status: Accepted
Related ITIS Name(s): Celastrus orbiculatus Thunb. (TSN 506068)
Unique Identifier: ELEMENT_GLOBAL.2.131407
Element Code: PDCEL03010
Informal Taxonomy: Plants, Vascular - Flowering Plants - Bittersweet Family
 
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Celastrales Celastraceae Celastrus
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Concept Reference
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Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Celastrus orbiculata
Taxonomic Comments: Sometimes erroneously referred to as C. articulatus.
Conservation Status
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NatureServe Status

Global Status: GNR
Global Status Last Changed: 22Mar1994
Rounded Global Status: GNR - Not Yet Ranked
Nation: United States
National Status: NNA
Nation: Canada
National Status: NNA (26Oct2017)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Arkansas (SNA), Connecticut (SNA), Delaware (SNA), District of Columbia (SNA), Georgia (SNA), Illinois (SNA), Indiana (SNA), Iowa (SNA), Kentucky (SNA), Maine (SNA), Maryland (SNA), Massachusetts (SNR), Michigan (SNA), Minnesota (SNA), New Hampshire (SNA), New Jersey (SNA), New York (SNA), North Carolina (SNA), Ohio (SNA), Pennsylvania (SNA), Rhode Island (SNA), South Carolina (SNA), Tennessee (SNA), Vermont (SNA), Virginia (SNA), West Virginia (SNA)
Canada New Brunswick (SNA), Nova Scotia (SNA), Ontario (SNA), Quebec (SNA)

Other Statuses

NatureServe Global Conservation Status Factors

Range Extent Comments: Celastrus orbiculatus is native to temperate east Asia, including central and northern Japan, Korea, and China north of the Yangtze River.

The exact date of Celastrus orbiculatus introduction to eastern North America is obscure, but appears to have been before 1879 (Patterson 1974). Patterson (1974) stated that C. orbiculatus has become "naturalized" in 21 of the 33 states in which it is cultivated. By the early 1970's it was naturalized north to central Maine, through New England, New York, Ohio and west to Iowa, south to Louisiana and Georgia. It was considered weedy in all of New England and most of the Atlantic Coast States by 1971. It is especially troublesome in the southern Appalachians and is considered epidemic in the vicinity of Asheville, North Carolina (Langdon 1993). Patterson (1974) also found it cultivated in the three Pacific Coast states, but it has not been reported "naturalized" there. It is reasonable to assume the vine has expanded its North American range in the twenty years since Patterson completed his research.

The western-most citation of naturalized populations found was for the "southeastern Great Plains" (Great Plains Flora Assoc. 1986). In southern Illinois, it is sometimes found in woodlands (Mohlenbrock and Voigt 1974), while the authors of "Plants of the Chicago Region" call it "an aggressive weed which gives every indication of being a future problem in the area" (Swink and Wilhelm 1979). C. orbiculatus is also "sometimes found in semi-natural situations, as in woods" in southern Ontario, Canada (Soper and Heimburger 1985).

Other NatureServe Conservation Status Information

Distribution
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Global Range: Celastrus orbiculatus is native to temperate east Asia, including central and northern Japan, Korea, and China north of the Yangtze River.

The exact date of Celastrus orbiculatus introduction to eastern North America is obscure, but appears to have been before 1879 (Patterson 1974). Patterson (1974) stated that C. orbiculatus has become "naturalized" in 21 of the 33 states in which it is cultivated. By the early 1970's it was naturalized north to central Maine, through New England, New York, Ohio and west to Iowa, south to Louisiana and Georgia. It was considered weedy in all of New England and most of the Atlantic Coast States by 1971. It is especially troublesome in the southern Appalachians and is considered epidemic in the vicinity of Asheville, North Carolina (Langdon 1993). Patterson (1974) also found it cultivated in the three Pacific Coast states, but it has not been reported "naturalized" there. It is reasonable to assume the vine has expanded its North American range in the twenty years since Patterson completed his research.

The western-most citation of naturalized populations found was for the "southeastern Great Plains" (Great Plains Flora Assoc. 1986). In southern Illinois, it is sometimes found in woodlands (Mohlenbrock and Voigt 1974), while the authors of "Plants of the Chicago Region" call it "an aggressive weed which gives every indication of being a future problem in the area" (Swink and Wilhelm 1979). C. orbiculatus is also "sometimes found in semi-natural situations, as in woods" in southern Ontario, Canada (Soper and Heimburger 1985).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
NOTE: The distribution shown may be incomplete, particularly for some rapidly spreading exotic species.

U.S. & Canada State/Province Distribution
United States ARexotic, CTexotic, DCexotic, DEexotic, GAexotic, IAexotic, ILexotic, INexotic, KYexotic, MA, MDexotic, MEexotic, MIexotic, MNexotic, NCexotic, NHexotic, NJexotic, NYexotic, OHexotic, PAexotic, RIexotic, SCexotic, TNexotic, VAexotic, VTexotic, WVexotic
Canada NBexotic, NSexotic, ONexotic, QCexotic

Range Map
No map available.

Ecology & Life History
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General Description: Celastrus orbiculatus is a deciduous woody vine. The branches are round, usually with noticeable lenticels. The outer surface of its roots are characteristically bright orange. 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 to 8 cm wide. Flowers are small and greenish-yellow with 5 sepals and 5 petals.
Technical Description: Celastrus orbiculatus is a deciduous woody vine which climbs by means of twining about a support. The branches are round, glabrous, light to darker brown, usually with noticeable lenticels. The outer surface of its roots are characteristically bright orange. Individuals have been found climbing to heights up to 18 m in the Great Smoky mountains (Langdon 1993). Plants with stems 5 cm diameter at breast height are common and some reach 13 cm dbh. Axillary buds are 1-3 mm long, 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 to 8 cm wide. Leaf margins are crenate-serrate and leaf base cuneate to obtuse, tip acute to rounded. Petioles are 1-3 cm long.

Inflorescences are axillary cymes, usually containing 3 - 7 flowers. However inflorescences are 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).

The flowers have 5 sepals and 5 petals. Male flowers contain 5 stamens which are about as long as the petals and inserted at the edge of a 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 embedded in the disk (Gleason and Cronquist 1991).

The fruit are globose, loculicidal capsules, 6 to 8 mm in diameter, which change in color from green to bright yellow as they mature. The capsules are three valved with each valve (locule) containing one or two 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 bicolored "dispersal flag".

Diagnostic Characteristics: This species can be reliably distinguished from the native Celastrus scandens only by the location of female flowers and fruit. In C. orbiculatus they are borne in clusters of 3 - 7 in the axils of leaves. Celastrus orbiculatus fruit are never arranged in terminal clusters. In contrast the flowers and fruit of C. scandens are borne in terminal panicles which may contain numerous flowers or fruits. A second, less reliable, difference is the yellow color of the outer fruit covering in C. orbiculatus vs. the orange color of C. scandens outer fruit cover. The color of the inner aril is red in both species. Identification by leaf shape or size, or by male inflorescence type is not reliable. Illustrations showing the differences between the two species can be found in Gleason (1952) and McNab and Meeker (1987).

The primary taxonomic reference for this section is Hou (1955).

Ecology Comments: Flowers bloom in late May to early June in Connecticut. Fruit ripens in September and remains on the vine through much of the winter. Brizicky (1964) notes that hymenopterous insects, especially bees, are its main pollinators, but Wyman (1950) also found wind pollination to be effective. Wyman also states C. orbiculatus and C. scandens can pollinate each other, and White and Bowden (1947) created a fertile hybrid through a controlled breeding program. No naturally occurring hybrid plants have been reported in the literature. However, Dreyer et al., (1987) reported two distinct sizes of pollen grains on certain individuals, tentatively identified as C. orbiculatus, growing in close proximity to C. scandens. They speculated that these plants may be hybrids.

Fruit dispersal is generally thought to be by birds and small mammals. In an unpublished undergraduate study in Connecticut, removal of fruit from seven species of woody plants by birds was observed during fall and winter (Wheeler 1987). C. orbiculatus was considered an important winter food, and was comparable in lipid and sugar content to the fruit of other species, but was not taken at all by animals in the fall. Black-capped Chickadees, Northern Mockingbirds, European Starlings and Blue Jays all fed on C. orbiculatus during the winter months.

Humans are also important dispersal agents. Fruiting stems are collected for dried flower arrangements, and are soon disposed of on compost and brush piles. The vine is highly attractive, easy to grow and propagate, and available at many nurseries, where it is often mislabeled as C. scandens. It was, and still may be, planted extensively in highway landscaping and for "conservation" plantings for wildlife food and cover, and erosion control, both as itself or mistakenly for C. scandens.

Seed germination is generally high in C. orbiculatus, particularly when compared to C. scandens. Patterson (1974) conducted a wide variety of germination tests with seed from 4 eastern U.S. states and found between 30 and 95% germination. He also noted that the highest germination rates occurred at low light intensities. Dreyer et al. (1987) confirmed the ability to germinate at low light levels and reported germination from 59 to 82%. Also in Connecticut, Clement et al. (1991) found C. orbiculatus produced 4.2 viable seeds per fruit compared to 3.2 in C. scandens. Mean germination rates for C. orbiculatus were 70% compared to 20 % for C. scandens.

In field experiments Clement et al. (1991) found that C. orbiculatus photosynthetic rates increased with increasing light intensity. In contrast, C. scandens photosynthetic rates at the same sites, tended to reach a plateau beyond which additional light had no significant effect. The ability of C. orbiculatus to acclimate to a variety of irradiance levels may be one of the factors which has allowed it to spread rapidly.

C. orbiculatus rootsuckers prolifically, especially after the main vine is damaged or cut. Rootsuckering is a common occurrence and results in large clones or patches which often spread from one or a few original plants which originated as seedlings.

Patterson (1974) noted the scarcity of other plants under dense canopies of C. orbiculatus, but could not attribute this to soil moisture, soil nutrients, precipitation interception or temperature changes. However, shading by the C. orbiculatus canopy was considered a potentially significant factor.

Habitat Comments: Celastrus orbiculatus habitat on its native continent of Asia is said to be lowland slopes or thickets at altitudes from 100 to 1,400 m. The vine is widely distributed in northern and central Japan and Korea. In China it is found primarily in provinces north of the Yangtze River (Hou 1955).

Its North American habitat preferences are wide but seem to be exclusively terrestrial. It is variously described as occupying open woods and thickets (Gleason and Cronquist 1991), roadsides, fence-rows, and thickets (Fernald 1970), alluvial woods, roadsides and thickets (Radford et al. 1968).

Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: Celastrus orbiculatus is an invasive, non-native woody vine. It is particularly troublesome in natural areas in coastal Connecticut and New York state and in the southern Appalachians but can be found growing wild from Maine to Louisiana and the southeastern Great Plains. It can severely damage desirable plants by strangling and/or overtopping them and can blanket entire stands. Upland meadows, thickets, young forests, and beaches are most vulnerable to Asian bittersweet invasion and dominance.

The species can be distinguished from its native congener C. scandens by the location of its fruit - C. orbiculatus has small clusters in the leaf axils while C. scandens has clusters at its branch tips. The two species may be capable of hybridizing and since the native is relatively rare it is possible that its distinct genetic identity is threatened.

Little research has been conducted on C. orbiculatus control but low-growing populations have been successfully treated by cutting and applying triclopyr herbicide to the regrowth about a month later. Larger vines can be cut and the stump treated immediately with triclopyr herbicide. Unfortunately, Asian bittersweet is frequently cultivated and its fruits are gathered for decorative use, which will make preventing further spread and reinfestation all the more difficult. For this reason it is of the utmost importance that land managers, naturalists, botanists, students, horticulturists, gardeners, retailers, etc. learn to distinguish between the native and the introduced bittersweet vine. The seriousness of the problem must be communicated to those in areas where C. orbiculatus either has not yet reached or is not well established.

Species Impacts: Celastrus orbiculatus poses a serious threat to individual plants and plant communities due to its high reproductive rate, long range dispersal, ability to rootsucker, and rapid growth rates. Individual plants can be severely damaged and even killed by the aggressive growth habits of this vine. Tree and shrub stems are weakened and killed by the twining and climbing growth that twists around and eventually constricts solute flow (as shown by Lutz, 1943 for C. scandens). Trees with girdled stems and large amounts of vine biomass in their canopies are more susceptible to damage by wind, snow and ice storms (Siccama, et al. 1976, Langdon 1993). All types of plants, and even entire plant communities, can be over-topped and shaded by the vine's rapid vegetative growth. Nearly pure stands of this vine are not uncommon in affected areas. Upland meadows, thickets and young forests, both natural and managed, appear to be most vulnerable to C. orbiculatus dominance.

Langdon (1993) notes that many of the rarest plants in the southeastern United States require a natural disturbance regimen of a certain quality and frequency. Because many of these processes have been altered some of these species are now relegated to roadway and utility corridors that provide exactly the sort of habitat most often invaded and dominated by C. orbiculatus. Langdon (1993) also points out that the region's old growth forests such as cove hardwood stands lose 1-2% of their canopy each year which may provide C. orbiculatus with opportunities to invade. Fortunately, it has not yet been found in virgin forests in the Great Smoky Mountains.

Beaches are also open to invasion. In Connecticut, The Nature Conservancy is managing a C. orbiculatus infestation in sand dunes adjacent to a Piping Plover nesting area on Long Island Sound. The managers are concerned that the vines will either spread into actual nesting areas or alter the dynamics of dune formation and erosion (Lapin 1992). In either case, they could interfere with the reproduction of a bird officially listed as a Threatened Species by the State of Connecticut. Very vigorous patches of C. orbiculatus have also been observed growing in pure sand in coastal Rhode Island (Dreyer, pers. obs.).

It is considered of particular concern to forestry programs in some parts of the southern United States (McNab and Meeker 1987). The problems throughout the East are most noticeable along roadsides where vegetation is blanketed by bittersweet in a way reminiscent of Kudzu infested areas of the southeastern United States.

Given the fact that hybrids with C. scandens are clearly possible, and that C. scandens appears to be less common than in the recent past (Dreyer et al. 1987, Mehrhoff 1986), the potential for introgressive hybridization, resulting in the loss of C. scandens genetic identity, is possible. Connecticut has recently listed C. scandens as a Species of Special Concern, i.e. one for which more information on distribution and abundance is needed. In Great Smoky Mountains National Park C. scandens is restricted to circumneutral soils and is considered a non-reproducing rare plant (Langdon 1993).

Restoration Potential: Recovery of natural areas highly infested with C. orbiculatus is unpredictable. Previous natural vegetation structure and function are often severely altered, although remnants of the flora may persist. Removal methods often further disrupt remnants of previous plant communities. A number of workers report that even with complete removal and rootkill of C. orbiculatus, substantial seedling regeneration occurs in following years, probably due to a persistent soil seed bank. Langdon (1993) stresses that individual clones are difficult to kill. For example, one 5m x 5m clone treated with triclopyr in 1986 has produced 50+ sprouts each year since. The sprouts are hand-pulled but often break and resprout later. Fortunately, the six years of work at this site appear to have nearly exhausted the seed bank. In cases where all nearby seed sources cannot be eliminated, however, reinfestation is a continual possibility.
Management Requirements: Effective biological and additional effective chemical/mechanical control methods are needed. Education of nursery growers, retailers, and the gardening public is also needed to reduce the demand for and the dissemination of the vine and its fruit.
Monitoring Requirements: Due to the ease of and apparent interest in cultivating C. orbiculatus in the eastern half of the United States and elsewhere, a very large geographic area is potentially threatened. The spread of the vine from coastal States westward should be monitored. In addition, the status of C. scandens populations, especially in east coast States, should be evaluated.

Langdon (1993) strongly suggests that natural areas be scouted for infestations about 2 weeks after the autumn foliage peak. In the Great Smoky Mountains this falls around November 10. By this time other native deciduous plants drop almost all of their leaves while C. orbiculatus leaves turn lemon- to golden-yellow making the plants easy to identify even at a distance or from a vehicle at moderate speeds. Since individual plants are usually exclusively male or female and the seeds may disperse a kilometer or more, these types of searches are essential to locate individuals that have recently become established in previously uninfested areas. If carried out conscientiously, such searches will enable managers to implement control programs that contain infestations to particular areas and prevent them from spreading. ½MONIT.PROG? The following individuals have experience monitoring and controlling Celastrus orbiculatus:

Glenn Dreyer, The Connecticut College Arboretum, 270 Mohegan Avenue, New London, CT 06320.

Lise Hanners, Devil's Den Preserve, P.O. Box 1162, Weston, CT 06883. Phone: 203-226-4991.

Keith Langdon, Great Smokey Mt. National Park, 107 Park Headquarters Road, Gatlinburg, Tenn. 37738. Phone: 615-436-1218.

Beth Lapin, TNC Connecticut Office, 55 High Street, Middletown, CT 06457. Phone: 203-344-0716.

W. Henry McNab, USDA Forest Service, SE Forest Experiment Station, Asheville, NC 28806.

David Patterson, USDA Ag. Research Service, Botany Department, Duke University, Durham, NC 27706.

Paula Piehl, Potomac State College, West Virginia University, Keyser, West Virginia 26726.


Management Programs: HERBICIDES: A successful control technique was developed by Dreyer (1988) for dense, low patches of C. orbiculatus where herbicide use is appropriate. Vegetation in the entire area is cut to the ground early in the growing season and allowed to resurge. Approximately one month later, foliar applications of an herbicide containing triclopyr (Garlon 4, a triclopyr ester, or Garlon 3A, a triclopyr salt) mixed at 1% to 2% in water and applied by backpack sprayer result in essentially 100% rootkill of C. orbiculatus. No off-target damage or root uptake by adjacent plants has been noted in over four years of using this technique. The same study found foliar applications of glyphosate (Roundup, Rodeo) and amitrole (Amitrol, Weedazol) were both ineffective in rootkilling C. orbiculatus.

Another advantage to using triclopyr instead of glyphosate is that it does not kill monocots. Thus grasses, sedges, liliaceous plants, etc., will not be killed and will remain to prevent soils from being completely exposed. These remaining plants often dominate sprayed sites a year after treatment. Triclopyr is also the active ingredient, in relatively dilute form, in the Ortho product Brush-B-Gone which, unlike Garlon, is not a restricted use chemical.

Hutchison (1992) reports foliar applications of a 2,4-D and triclopyr mixture (Crossbow) to C. orbiculatus will effectively "reduce the population" when applied in mid to late October.

In locations where large vines climb high into trees, cutting and treating the vine stump surface with a triclopyr-containing herbicide is a logical procedure. The vine stems hanging in the trees will decompose and fall within two to three years. Hutchison (1992) recommends cut surface treatment with "100% Roundup" (presumably undiluted with water) applied at the time of the last killing frost, but he included no data concerning the effectiveness of this technique.

MOWING: Regular, weekly mowing will exclude C. orbiculatus. However, less frequent mowing, eg. 2-3 mowings per year, stimulates rootsuckering (Dreyer, pers. obs.).

CONTACTS WITH ADDITIONAL INFORMATION ON CONTROL: In addition to the Connecticut College Arboretum program described above, the following organizations have some type of C. orbiculatus control programs or experience:

Connecticut DOT, Contact: James Stotler, Conn. DOT, 24 Wolcott Hill Rd., Drawer A, Wethersfield, CT 06109.

Great Smokey Mountains National Park (Contact is Keith Langdon, see MONITORING PROJECTS section above for address).

Max Hutchison, Cache River Wetlands Project, The Nature Conservancy, Route 1, Box 53E, Ullin, Illinois, 62992. Phone: 618-634-2524.

Southeastern Forest Experiment Station (contact is W. Henry McNab, see MONITORING PROJECTS section above for address).

TNC Connecticut (Contact Beth Lapin, see MONITORING PROJECTS section above for address).

Management Research Programs: Researchers at the Connecticut College Arboretum and the College's Botany and Zoology Departments (Dreyer, Clement, Wheeler, etc.) have pursued various aspects of the problem. No projects are currently underway. Future research will probably continue to examine the comparative species biology of C. scandens vs. C. orbiculatus. No other active research programs are known.
Population/Occurrence Delineation Not yet assessed
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Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank)
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Disclaimer: While I-Rank information is available over NatureServe Explorer, NatureServe is not actively developing or maintaining these data. Species with I-RANKs do not represent a random sample of species exotic in the United States; available assessments may be biased toward those species with higher-than-average impact.

I-Rank: High/Medium
Rounded I-Rank: High
I-Rank Reasons Summary: Celastrus orbiculatus reduces system-wide light levels and alters community structure and composition by overtopping existing vegetation and shading lower layers (Dreyer 1994; Miller 2003). It is reported invasive in much of its range and listed as a noxious weed in Vermont (USDA-NRCS 2004). It invades a number of habitat types including at least beach dunes, meadows, forest edges, and disturbed forests (Dreyer 1994, Miller 2003; D. Taylor pers. comm. 2007). Experts believe the range is expanding (Dreyer 1994, D. Taylor pers. comm. 2007). Seeds are dispersed by birds (Dreyer 1994). The species is used for ornamental purposes, further contributing to its spread (Dreyer 1994). A long-lived seed bank increases overall management difficulty; control may therefore take over five years to achieve (Dreyer 1994). May contribute to the decline of the native C. scandens through competition and, potentially, hybridization; the extent of natural hybridization between these two species requires further investigation.
Subrank I - Ecological Impact: Medium/Low
Subrank II - Current Distribution/Abundance: High
Subrank III - Trend in Distribution/Abundance: High/Medium
Subrank IV - Management Difficulty: Medium
I-Rank Review Date: 25Sep2007
Evaluator: Heffernan, K., minor rev. K. Gravuer
Native anywhere in the U.S?
Native Range: Temperate east Asia, including central and northern Japan, Korea, and China north of the Yangtze River (Dreyer 1994)

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Screening Questions

S-1. Established outside cultivation as a non-native? YES
Comments: (Dreyer 1994; Bergman and Swearingen 1997).

S-2. Present in conservation areas or other native species habitat? Yes
Comments: Beach, dune, and meadows in northeast; forests in southeast (Dreyer 1994; Miller 2003; D. Taylor pers. comm. 2007).

Subrank I - Ecological Impact: Medium/Low

1. Impact on Ecosystem Processes and System-wide Parameters:Low significance
Comments: Blankets vegetation in some habitats (e.g. young forest), reducing system-wide light levels (D. Taylor pers. comm. 2007).

2. Impact on Ecological Community Structure:High significance
Comments: Overtops existing canopy (Dreyer 1994; Miller 2003).

3. Impact on Ecological Community Composition:High significance
Comments: Severely reduces native plants by strangling or overtopping (Dreyer 1994). Can "devastate young woody growth" (D. Taylor pers. comm. 2007).

4. Impact on Individual Native Plant or Animal Species:Medium/Low significance
Comments: In controlled crosses between C. orbiculata and C. scandens, between-species crosses produced nearly as many viable seeds as within-species crosses using only C. scandens (Pooler et al. 2002), and a few reports of hybridization between these two species in the wild are known (e.g. L. Mehrhoff pers. comm. cited in Pooler et al. 2002). Assessment of the extent of natural hybridization is greatly needed; because it is difficult to identify hybrids when plants are not flowering or fruiting, the extent of natural hybridization may be greater than currently realized. The potential for natural hybridization is of concern, as preliminary results show that hybrids tend to be faster growing and have shorter seed dormancy than pure C. scandens (Pooler et al. 2002). Furthermore, Steward et al. (2003) documented a concurrent decline of C. scandens and expansion of C. orbiculata in the New York City metropolitan area, and considered whether C. orbiculata spread may be contributing to the decline of C. scandens. Given that these species occasionally co-occur and that C. orbiculata exhibits greater fecundity, more vigorous and aggressive growth, and higher pollen and seed viability than C. scandens (Steward et al. 2003 and references therein), it is possible that C. orbiculata is having a disproportionate impact on C. scandens even if further research shows that natural hybridization is not widespread.

5. Conservation Significance of the Communities and Native Species Threatened:Unknown
Comments: No data in referenced literature.

Subrank II. Current Distribution and Abundance: High

6. Current Range Size in Nation:Moderate significance
Comments: All Northeastern and Mid-Atlantic states, most Mid-western states, Georgia, South Carolina, Tennessee, and Arkansas (Kartesz and Meacham 1999. USDA-NRCS 2004).

7. Proportion of Current Range Where the Species is Negatively Impacting Biodiversity:High significance
Comments: Reported as invasive in Maine, New York, Ohio, Virginia, Tennesse, Kentucky, and Wisconsin; list as noxious weed in Vermont (USDA-NRCS 2004; Bugwood Network 2004). Also reported invasive in Arkansas, Georgia, South Carolina, North Carolina (Miller 2003).

8. Proportion of Nation's Biogeographic Units Invaded:Moderate significance
Comments: Less than 20 TNC ecoregions (Heffernan, pers. obs., using USDA-NRCS 2004; Slaats 1999).

9. Diversity of Habitats or Ecological Systems Invaded in Nation:Moderate significance
Comments: Beach, dune, meadows, forest edges, disturbed forests (Dreyer 1994; Miller 2003; D. Taylor pers. comm. 2007).

Subrank III. Trend in Distribution and Abundance: High/Medium

10. Current Trend in Total Range within Nation:Moderate significance
Comments: Probably expanding overall (Dreyer 1994; Ma and Moore 2003); known to be moving eastward in Kentucky (D. Taylor pers. comm. 2007).

11. Proportion of Potential Range Currently Occupied:Unknown
Comments: In Kentucky, well-established on limestone soils and is expanding eastward into more acid sites (D. Taylor pers. comm. 2007).

12. Long-distance Dispersal Potential within Nation:High/Moderate significance
Comments: Dispersal by birds and humans (Dreyer 1994).

13. Local Range Expansion or Change in Abundance:Moderate significance
Comments: Locally expanding in at least Kentucky (D. Taylor pers. comm. 2007).

14. Inherent Ability to Invade Conservation Areas and Other Native Species Habitats:High/Moderate significance
Comments: Benefits from but does not require disturbance to become established; described as an aggressive invader that can dominate all levels of forest and open areas (Ma and Moore 2003).

15. Similar Habitats Invaded Elsewhere:Unknown
Comments: No data in referenced literature.

16. Reproductive Characteristics:Moderate significance
Comments: Quickly spreading vines; resprouts following cutting (Dreyer 1994) or burning (D. Taylor pers. comm. 2007).

Subrank IV. General Management Difficulty: Medium

17. General Management Difficulty:Moderate significance
Comments: Triclopyr herbicide combined with mowing is effective (Dreyer 1994). Burning or grazing with goats are not effective techniques (D. Taylor pers. comm. 2007).

18. Minimum Time Commitment:Moderate significance
Comments: Minimum six years treatment to exhaust the seed bank (Dreyer 1994).

19. Impacts of Management on Native Species:Moderate significance
Comments: Triclopyr herbicide does not kill monocot species, thus allowing for quick reocvery of those species following control (Dreyer 1994).

20. Accessibility of Invaded Areas:Insignificant
Comments: No mention of accessibility issues in literature referenced.

Other Considerations: The publication at the following web link describes how to differentiate Oriental Bittersweet (C. orbiculatus) from American Bittersweet (C. scandens): http://www.glsc.usgs.gov/_files/factsheets/2007-2%20Identifying%20Bittersweet.pdf
Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 03May1994
NatureServe Conservation Status Factors Author: GLENN D. DREYER, CONNECTICUT COLLEGE ARBORETUM, 270 MOHEGAN AVENUE, NEW LONDON, CT 06320
Management Information Edition Date: 03May1994
Management Information Edition Author: GLENN D. DREYER, CONNECTICUT COLLEGE ARBORETUM, 270 MOHEGAN AVENUE, NEW LONDON, CT 06320
Management Information Acknowledgments: Keith Langdon of Great Smoky Mountains National Park contributed important information on the biology and control of C. orbiculatus in the southern Appalachians. Beth Lapin of The Nature Conservancy's Connecticut Field Office provided valuable editorial comments.
Element Ecology & Life History Edition Date: 03May1994
Element Ecology & Life History Author(s): GLENN DREYER

Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

References
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