Oriental bittersweet is Celastrus orbiculatus, which according to Wikipedia has leaves that are round and glossy, which is not how I would describe the leaves pictured in that article. However, there are better ways to distinguish it from American bittersweet, Celastrus scandens. See Celastrus orbiculatus (Oriental Bittersweet): Minnesota Wildflowers and Celastrus scandens (American Bittersweet): Minnesota Wildflowers Those pages point out that the invasive one, Oriental bittersweet, is often sold as American bittersweet. And they hybridize, with the hybrid acting like the invasive one.
