Oriental bittersweet (Celastrus orbiculatus)
Oriental Bittersweet is a deciduous, woody vine native to China, Korea, and Japan1. It is extremely shade tolerant and grows in forests, woodland edges, grasslands, roadsides, and fencerows. It was brought to the United States in the mid 1800s as an ornamental plant and has since escaped and spread throughout the eastern US, Ontario, and Quebec2. Oriental Bittersweet is found in isolated patches throughout the Credit River Watershed.
Oriental Bittersweet grows by twining around shrubs and trees. It can reach a height of up 30 m where tall trees are present3. It has alternating glossy leaves that are rounded with finely toothed edges. The stems are light brown, with noticeable lenticels and have solid white piths. The roots of the plant have a characteristic orange colour4. Oriental Bittersweet is dioecious, meaning there are separate male and female plants. It blooms May to June, producing greenish yellow flowers in the leaf axils. Female plants produce round leathery seed pods that are green at first but turn a bright yellow or orangish yellow in fall. The seed pods open to reveal a red fruit which contains three to six seeds5. These seeds are distributed by birds that eat the fruit.
Oriental Bittersweet can easily overrun native vegetation, forming nearly pure stands. It can strangle shrubs and small trees and weaken or even kill mature trees, by girdling the trunk and smothering the crown4. Oriental Bittersweet prolifically reproduces both by seed and by spreading its underground roots, which are capable of sprouting new stems2. Because of this, it is a major threat to any ecosystem it invades. There is also evidence that it can hybridize with the native American Bittersweet (C. scandens)4. Hybridization between American Bittersweet and Oriental Bittersweet could result in the genetic elimination of American Bittersweet4. The American Bittersweet is distinguished by flowers clustering at the tips of its branches, while Oriental Bittersweet has flower clusters along the leaf axils3.
Oriental Bittersweet can become a serious problem if not detected and removed early. It can be removed by pulling or digging, provided the root is removed entirely. If the plant is female, it should be removed before it goes to seed. Herbicides applied directly to foliage, cut stumps, basal bark, or stem injection are generally the most effective means in which to control populations of Oriental Bittersweet3.
*CVC is interested in any locations of Oriental Bittersweet and is tracking the population within our watershed. If you think you have located Oriental Bittersweet, please contact CVC via email and call the Ontario Federation for Anglers and Hunters Invasive Species Hotline at 1-800-563-7711 and add the sighting to the EDDMaps Ontario website.
https://www.youtube.com/watch?v=7wmZ1Zuho1c (Video created by the University of Michigan)
- Swearingen, J. 2009. “Fact Sheet: Oriental Bittersweet”. Plant Conservation Alliance’s Alien Plant Working Group. Web. 16 August 2018. https://www.invasive.org/alien/fact/pdf/ceor1.pdf
- Fire Effects Information System. “Celastrus orbiculatus”. United States Forest Service. Web. 16 August 2018. https://www.fs.fed.us/database/feis/plants/vine/celorb/all.html
- Michigan Natural Features Inventory. 2012. “Invasive Species Best Control Practices: Oriental Bittersweet (Celastrus orbiculatus)”. Michigan Department of Natural Resources. Web. 16 August 2018. https://mnfi.anr.msu.edu/invasive-species/OrientalBittersweetBCP.pdf
- Invasive Plant Species Assessment Working Group. 2006. “Invasive plant species fact sheet. Oriental Bittersweet (Celastrus orbiculatus)”. Web. 16 August 2018. http://www.inpaws.org/wp-content/uploads/Oriental_Bittersweet.pdf
- Midwest Invasive Plant Network. 2012. “New invasive plants of the Midwest fact sheet: Asian Bittersweet (Celastrus orbiculatus)”. Web. 16 August 2018. https://bugwoodcloud.org/mura/mipn/assets/File/Midwest20Invasives%0Fact20Sheets/abitt.pdf