Oriental bittersweet was introduced into North America in 1860 and has spread widely, principally with the help of birds, animals, and humans. The berries that appear in the spring will later become an attractive feature of the plant as well as food for birds and animals.
In the fall, oriental bittersweet can be quite attractive. At that time of year the outer covering of the berries turns yellow, and, as these husks split open, they reveal a red-orange berry. Because the color combination is so attractive, people cut off branches to use in floral arrangements. Unfortunately, the berries are often disbursed when the arrangement is thrown away, helping the spreading of the vine.
The yellow husked bittersweet fruits are about 1/4 inch across, appearing from July to October. The yellow ovary walls begin to fall from the fruit after the first frost. The fruit splits open at maturity revealing three red-orange axils that contain the seeds.
Like all living things, bittersweet serves a purpose in the ecosystem. It provides food and shelter for some animals.
Despite providing some benefits, bittersweet tends to run out of control to the detriment of the forest around it. It thrives best in sunny areas, but also survives in deep shade. In Marblehead, it can be found almost anywhere, but is most invasive in the Hawthorn Pond, Ware Pond, and Steer Swamp conservation areas. It is also widespread along the Path that follows the old railroad bed.
Bittersweet damages other plants in a number of ways:
* Shading blocks their light.
*The vine girdles the plants, cutting off their circulation.
*The weight of the vines causes branches and entire trees to collapse from the weight, especially during snowstorms.
Bittersweet is a deciduous, woody, perrenial vine. The brownish vines have been found to grow in Marblehead as much as sixty feet long and over seven inches in diameter! The stems have a dark brown to brown-striated bark. Twigs are dark brown, brown, or light gray and are smooth and hairless.
* The common name is Oriental bittersweet, Asiatic bittersweet, Round-leaved bittersweet and the full scientific name is Celastrus orbiculatus Thunb.
* The alternate, spiral leaves have only one per node. They are evenly placed around the stem. Leaves have a light green color and are widely elliptic or ovate to obovate or circular.
* Buds, and flowers that bloom in May or June, are axillary in their position on the stem. There are 3-4 very small (1/10 inch or so) greenish flowers per inflorescence.
* Celastrus orbiculatus is easy to confuse with native bittersweet (C. scandens). The main difference between the two plants is the location of the inflorescence. The inflorescence of C. scandens is located terminally and not axillary on the stems. Another, but not always consistent feature is the color of the ovary walls. In the fall, the color of the ovary walls in C. orbiculatus are yellow while C. scandensis a darker orange color that does not contrast as much with the red arils.
* A threat is the possibility of it displacing American bittersweet (C. scandens). C. scandens does not exhibit this aggressive nature, but it can hybridize with C. orbiculatus.