Plants have been a part of this planet longer than humans have and are essential to our lives. They come in many varieties and provide us many different uses, leading to their travel across the globe with the people that appreciate them. In some cases, about 1 in 1000, one of these plants is brought to a place where it is able to thrive so well that it crowds out the local plant life. This is the case with oriental bittersweet (Celastrus orbiculatus), a climbing, woody vine that is now a problem in most of the eastern US.
Oriental bittersweet, also known as round-leaved or Asian bittersweet, originated in eastern Asia. It was brought to the US in the 1860s to be used in gardens for decoration. To this day, it is still sold in many plant nurseries and is often used in decorative wreaths.
Why it’s a problem:
Oriental bittersweet negatively impacts native plants in several ways. Initially it is a competitor to other plant species, using up light and soil resources. In addition to that, it has no natural predator in the US, meaning there are no animals that eat it and no plants that block its growth. Once it gets a hold in a forest area, this vine, unlike many native vines, causes harm to the tree or shrub it grows around by wrapping so tightly around the bark that nutrients are unable to move upward from the roots. Oriental bittersweet can also add significant weight to the tops of trees, causing them to fall in high winds. (Photo of a sapling freed from girdling by a bittersweet vine by Nicole Myers
How to identify it:
The woody appearance of the vine makes bittersweet easy to identify when comparing to some vines like English Ivy; Leaves are arranged alternately along the stem and can vary widely in shape, being round, oblong or teardrop-shaped with finely toothed margins and sometimes with a long, tapering point.
Oriental bittersweet has an American relative (Celastrus scandens) with which it can hybridize. The primary differences are in the leaf shape, which on the exotic plant are smaller and rounder than the native’s leaves, and in the cluster of flowers and fruits, which appear in the leaf axils on the invasive species as opposed to the tips of the branches in the native vine. (Photo of bittersweet vine and leaves by Mike Sowers)
How to stop it:
Oriental bittersweet can be removed at any time of year by pulling or digging it out by the roots. For larger vines, cut a window out of the vine, cutting close to the ground and then some distance higher. Using herbicide is most effective in early spring or late fall and is typically not recommended for use except by a certified applicator. After cutting the vine, immediately paint the stump with an herbicide like glyphosate or triclopyr. You can also spray the leaves with herbicide such as 2,4-D plus triclopyr, or triclopyr alone. However, you must be very careful not to get the herbicide on the plant it is climbing. When removing bittersweet by hand, disposal varies based on whether or not there are fruit present. When the fruit are present, bag the vine and remove it from the area; otherwise, leaving the vine and its roots on top of the forest floor to break down is appropriate.
Now that you know a little more about this terrible invasive plant, remember not to buy it or throw the fruits out in the woods. To help protect the native biodiversity from this vine, join the Carroll County Weed Warriors for a weeding this spring! E-mail firstname.lastname@example.org for more information!
Information for this article came from: http://na.fs.fed.us/spfo/invasiveplants/factsheets/pdf/oriental-bittersweet.pdf