Found this article on the CT Master Gardeners facebook page.
Question: I’ve heard you shouldn’t use oriental bittersweet in wreaths, but American bittersweet is okay. Why is this, and how can I tell them apart?
Answer: The beautiful berry-studded vines of bittersweet are popular with crafters, but the trouble with oriental bittersweet (Celastrus orbiculatus) is that it is invasive. If you use it in your outdoor holiday decorations, birds may eat the berries and drop the seeds where they will sprout. Also, when the decorations are tossed at the end of the season, the vines can sprout from compost piles.
Left unchecked, this invasive species can overtake and destroy wooded areas by strangling small saplings and spreading throughout the canopy, preventing sunlight from reaching the forest floor. The weight of the vines can cause trees to topple. Oriental bittersweet is considered a noxious weed in Minnesota.
If you like the look of vines with berries in your arrangements, you do have options. American bittersweet (Celastrus Scandens), is native to the eastern United States, including Minnesota. It can climb our native trees without harming them, and it actually produces larger and showier berries than oriental bittersweet. There are several distinctive characteristics that can aid in identification of the two varieties:
If you are unsure about the berries in your holiday arrangement, it is important to dispose of it in a manner that does not support propagation: Add it to the logs in the fireplace, or place it in a plastic bag and dispose of it in the trash.
More information about identification and eradication resources may be found at: myminnesotawoods.umn.edu/wp-content/uploads/2011/08/gupta.chandler.2013.UMN-Extension.oriental-bittersweet.v1.1.pdf.