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Nature Notes

The Bittersweets--American and Oriental

When looking for a festive red-berried arrangement, or looking through seed catalogs with an eye to making your own in the future, be sure to check the identity of the bittersweet and only purchase the American species. If you have an old wreath of the Oriental species, please dispose of it properly. Your local trees and wildlife will thank you!

Invasive species are seemingly everywhere—our forests, prairies and rivers—but in our decorative wreaths? Unfortunately, yes.

Bittersweet vines have long been used as fall and winter decorations. Originally, the American Bittersweet (Celastrus scandens) was used, but increasingly the non-native, invasive Oriental Bittersweet (Celastrus orbiculatus) is being wrapped into wreaths. If these wreaths are improperly disposed of, Oriental Bittersweet can become established, causing massive problems for local natural areas.

Oriental Bittersweet is a woody vine that can grow 40-50 feet into tree canopies. With vines of up to six inches in diameter, it can strangle and smother entire forest stands. It can dominate tree canopies and reduce forest floor light to levels that prevent other plant species from growing. The vine weight, combined with snow and ice or high wind, can literally break trees. Heavy infestations result in swaths of downed trees covered with thickets of Oriental bittersweet vines. Because of its aggressive nature, several states, including Connecticut, Massachusetts, Minnesota, New Hampshire, North Carolina, Vermont and Wisconsin have banned the sale of Oriental Bittersweet.

At Kankakee Sands, we have both species. American Bittersweet is found throughout the Kankakee Sands project, and is a common, well-behaved resident. Oriental bittersweet is found in scattered locations, particularly near the south end of Willow Slough Fish and Wildlife area.

They can be somewhat difficult to tell apart. In the field, or in crafts, there are a few key differences to look for: Oriental Bittersweet has yellow seed capsules on red berries, while American Bittersweet has orange seed capsules on red berries. Oriental bittersweet has berries strung-out along the stem, with a few berries next to the leaf buds, while American bittersweet’s berries are in larger clusters near the end of the stems.

When we use Oriental bittersweet fruiting branches to make seasonal arrangements, we are inadvertently moving seed to new locations. If these arrangements are placed outside, birds can eat the fruit and move the seed. Composting old arrangements can also result in new infestations. Existing arrangements containing Oriental bittersweet should be bagged or burned for disposal.

This winter, if you are looking for a festive red-berried arrangement, or looking through seed catalogs with an eye to making your own in the future, be sure to check the identity of the bittersweet and only purchase the American species. If you have an old wreath of the Oriental species, please dispose of it properly. Your local trees and wildlife will thank you!

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