Saturday, May 19, 2012

The Oriental Bittersweet - Illinois Invasive Plant

On the "Illinois Most Wanted" list for invasive plants is the Oriental Bittersweet.

What is Oriental Bittersweet?
Oriental bittersweet is a deciduous woody perennial plant which grows as a climbing vine and a trailing shrub. Stems of older plants 4 inches in diameter have been reported. The leaves are alternate, glossy, nearly as wide as they are long (round), with finely toothed margins. There are separate female (fruiting) and male (non-fruiting) plants. Female plants produce clusters of small greenish flowers in axillary clusters (from most leaf axils), and each plant can produce large numbers of fruits and seeds. The fruits are three-valved, yellow, globular capsules that at maturity split open to reveal three red-orange, fleshy arils each containing one or two seeds. The abundance of showy fruits have made Oriental bittersweet extremely popular for use in floral arrangements.

IMPORTANT: Because Oriental bittersweet can be confused with our native American bittersweet (Celastrus scandens) which is becoming less and less common, it is imperative that correct identification be made before any control is begun. Contact your local arborist or tree service.  A professional tree service like Trees "R" Us, Inc. will have highly qualified arborists on staff to quickly assess your plants and have the qualified staff to take care of them for you.  
American bittersweet produces flowers (and fruits) in single terminal panicles at the tips of the stems; flower panicles and fruit clusters are about as long as the leaves; the leaves are nearly twice as long as wide and are tapered at each end. 
Oriental bittersweet produces flowers in small axillary clusters that are shorter than the subtending leaves and the leaves are very rounded. 
Comparing the two, American bittersweet has fewer, larger clusters of fruits whereas Oriental bittersweet is a prolific fruiter with lots and lots of fruit clusters emerging at many points along the stem. Unfortunately, hybrids of the two occur which may make identification more difficult.  I highly recommend you contact Trees "R" Us, Inc. or your local tree care provider for assistance in identification of Oriental Bittersweet and its treatment or removal if you have it infesting your yard.

Oriental bittersweet is an ecological threat.  It 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.

Oriental bittersweet currently occurs in a number of states from New York to North Carolina, and westward to Illinois. It has been reported to be invasive in natural areas in 21 states (CT, DE, IL, IN, KY, MA, MD, ME, MI, MO, NC, NH, NJ, NY, PA, RI, TN, VA, VT, WI, and WV) and at least 14 national parks in the eastern U.S.

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.

Oriental bittersweet reproduces prolifically by seed, which is readily dispersed to new areas by many species of birds including mockingbirds, blue jays and European starlings. The seeds germinate in late spring. It also expands vegetatively through root suckering.

Manual, mechanical and chemical control methods are all effective in removing and killing Oriental bittersweet. Employing a combination of methods often yields the best results and may reduce potential impacts to native plants, animals and people. The method you select depends on the extent and type of infestation, the amount of native vegetation on the site, and the time, labor and other resources available to you. Whenever possible and especially for vines climbing up trees or buildings, a combination of cutting followed by application of concentrated systemic herbicide to rooted, living cut surfaces is likely to be the most effective approach. 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.

No biological controls are currently available for this plant.

A basal bark application, cut stem application, foliar application, manual and mechanical applications
are all also possible.  Contact Trees "R" Us, Inc. or your local tree service for more information on these different types of applications.
Trees "R" Us, Inc. services the North Shore area of Chicago and its surrounding suburbs.  With experience in the tree care and maintenance industry since the 1990s, we are highly qualified in all areas of tree and plant care, removal and treatment.  Our highly qualified staff and arborists work hard to make sure your job, what ever it may be, is done correctly, safely and with 100% satisfaction.
For all your tree and plant health care needs, contact Trees "R" Us, Inc. through our website at, or give us a call at 847-913-9069.  

Thanks for reading, 

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