Oriental bittersweet (Invasive Plants of Maryland)

Oriental bittersweet

Celastrus orbiculatus

Description and biology ¹¹

Plant: deciduous, woody, twining vine, sometimes occurring as a trailing shrub; stems of older plants can reach 4 in. in diameter.
Leaves: alternate, glossy and rounded with finely toothed margins.
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 fleshy red-orange arils that cover the seeds; seeds germinate in late spring.
Spreads: by seed, which is dispersed to new areas by many species of birds and by people who are not responsible when disposing of faded bittersweet wreaths and other floral decorations; it expands locally by stolons and rhizomes and through root suckering (the ability to send shoots up from the roots).
Look-alikes: is easily confused with the native American bittersweet (Celastrus scandens), which produces flowers just at the terminal ends (stem tips) rather than from multiple leaf axils as in the exotic invasive. For this reason, it is important to correctly identify the vine before controls are attempted.

Ecological threat in the united states ¹²

Oriental bittersweet is a vigorously growing vine that climbs over and smothers vegetation which may die from excessive shading or breakage. When bittersweet climbs high up on trees the increased weight can lead to uprooting and blow-over during high winds and heavy snowfalls. In addition, Oriental bittersweet is displacing our native American bittersweet (Celastrus scandens) through competition and hybridization.

Habitat in the united states ¹³

Oriental bittersweet infests forest edges, woodlands, fields, hedgerows, coastal areas and salt marsh edges, particularly those suffering some form of land disturbance. While often found in more open, sunny sites, its tolerance for shade allows oriental bittersweet to invade forested areas.

Management ¹⁴

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.

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.

Biological Research Needs: Research in species biology is needed in the following areas: pollination ecology; extent of natural hybridization with C. scandens; mechanisms of seed dispersal; annual vegetative growth rates; mechanisms of rootsucker induction; possible allelopathic effects on other species; seed bank dynamics.

Research is also needed to define the current range of C. orbiculatus and to monitor subsequent spread.

Work on biological control methods is apparently completely lacking. Langdon (1993) located an ornamental planting of C. orbiculatus in north Georgia that was losing vigor due to an infestation of Euonymus scale (Unaspi euomyi) and suggests this lead should be followed. The little published on chemical and mechanical control indicates further work in these areas would also be fruitful.

Prevention and control ¹⁵

Do not buy, plant, transplant Oriental bittersweet or dispose of live or dead seed-containing material. Manual, mechanical and chemical methods can be employed to control it. Vines can be pulled out by the roots, cut repeatedly or treated with systemic herbicides. No biological controls are currently available for this plant.

Description ¹⁶

Deciduous twining shrubs; branchlets glabrous, gray- brown or brown, with sparse and inconspicuous lenticels; axillary buds small, ovate to elliptic, 1-3 mm. Petiole slender, 1-2 cm; leaf blade generally broadly ovate, suborbicular, or rectangular-elliptic, 5-13 × 3-9 cm, glabrous or abaxially sparsely pubescent on veins, base broadly cuneate to obtuse-orbicular, margin serrate, apex broadly rounded, muriculate, or shortly acuminate; secondary veins 3-5 pairs. Cymes axillary, sometimes terminal, 1-3 cm, 1-7-flowered; pedicels jointed below middle or nearly to base. Male flowers: sepals obtuse-triangular; petals obovate-elliptic to rectangular, 3-4 × 2-2.5 mm; disk shallowly cupuliform, lobe shallow, apex rounded-obtuse; stamens 2-3 mm. Female flowers: corolla relatively shorter than that of male flower; disk slightly thick, carnose; staminodes very short; ovary approximately globose; styles ca. 1.5 mm; stigma deeply 3-lobed, lobe apex shallowly 2-lobed. Capsule approximately globose, 8-13 mm wide, yellow, 3-valved. Seeds elliptic, slightly flat, 4-5 × 2.5-3 mm, reddish brown; aril orange-red. Fl. May-Jun, fr. Jul-Oct.

Sources and Credits

(c) Elizabeth Sellers, some rights reserved (CC BY-NC-SA), http://www.flickr.com/photos/76276920@N00/4651430506
Qwert1234, no known copyright restrictions (public domain), https://upload.wikimedia.org/wikipedia/commons/1/18/Celastrus_orbiculatus_081202.JPG
(c) Alpsdake, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/f/f4/Celastrus_orbiculatus_fruits.JPG
Qwert1234, no known copyright restrictions (public domain), https://upload.wikimedia.org/wikipedia/commons/8/8d/Celastrus_orbiculatus_080614.JPG
(c) Dalgial, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/e/e1/Celastrus_orbiculatus_01.JPG
(c) Dalgial, some rights reserved (CC BY-SA), https://upload.wikimedia.org/wikipedia/commons/7/7d/Celastrus_orbiculatus_02.JPG
(c) Priyantha Wijesinghe, some rights reserved (CC BY-NC), uploaded by Priyantha Wijesinghe
(c) samuelcr, some rights reserved (CC BY-NC)
no rights reserved, uploaded by Ira Gershenhorn
(c) kaitlyn0508, some rights reserved (CC BY-NC)
(c) Unknown, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/22734031
(c) Unknown, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/22948554
(c) Unknown, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/22948556
(c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/29047112
(c) Unknown, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/22734032
(c) Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/4971205

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