Photo by Sarah Squires
Oriental bittersweet, an invasive species, can cause devistation to natural forests in the area. Similar to American bittersweet, the Oriental variety has yellow berry casings, as opposed to the more orange colored cases found on the native variety.
The Emerald Ash Borer is old hat; an invasive species, the Oriental bittersweet plant, is here and growing, well, like a weed in the region.
Unlike the Emerald Ash Borer, Oriental bittersweet is not discriminatory. It targets just about anything it can climb, snaking up trees and often killing them in the process.
The woody vine is native to Eastern Asia, Korea, China, and Japan. It was first introduced to the area as an ornamental planting and in floral wreaths. Some residents still maintain the plant in landscapes and gardens. Because of the threat the invasive vine poses to native forests, however, Minnesota statutes prohibit the transportation, propagation or sale of Oriental bittersweet.
Entire plant communities may be overwhelmed by Oriental bittersweet, and a "large infestation" has been confirmed in Winona, according to the Minnesota Department of Agriculture. The best way to combat the invading vine is to learn how to spot it and get rid of it, experts agree.
Jhad Fetting, a forester and certified arborist, has worked to eliminate the pest from areas in Winona County. It is easy to confuse the plant with American bittersweet, he said, and there are several characteristics that people can use to determine whether they have found the Oriental variety. "The characteristics of Oriental bittersweet are the more rounded leaves and the fruit clusters emerging at many points along the branch stems," he explained. "This differs from the native American bittersweet, which produces fruit only at the ends of branches and has a longer, more slender leaf. Also, the native bittersweet has an orange capsule that covers the berries, as opposed to yellow on Oriental."
Because Oriental bittersweet produces many more berries than the American variety, it proliferates rapidly. The vines grow quickly and can reach lengths of 66 feet. "As the vine grows up the tree it can wrap around the stem, deforming and girdling the tree. The vine then begins to weigh down the tree, causing it to break during wind, snow, or ice storms," explained Fetting. "Then, once the tree has toppled, the vine continues to spread over the debris, creating a mat that prevents regeneration of new trees. This ruins our native forest."
The vines should be cut back and the stump should be killed using an herbicide or other method. Simply trimming back the vines can cause the bittersweet to grow back and sometimes spread. The Minnesota Department of Agriculture recommends a foliar or stump herbicide application, or consulting an expert.
The Minnesota Forest Pest First Detectors program is being used to train volunteers to help detect and destroy Oriental bittersweet. Trainers were in Winona Thursday helping volunteers identify the invasive species.
More information about Oriental bittersweet can be found by visiting the Minnesota Department of Agriculture web site