This past Saturday, Bernardo and I spent more time trying to distinguish between American and Oriental Bittersweet than actually ridding the garden of it.  Needless to say, we left most of it in place but pulled some down off of of a small tree to prevent any future harm, and to provide an up-close photo for you viewers to help us identify.
Oriental Bittersweet (Celastrus orbiculatus) is an aggressive and invasive climbing deciduous woody vine.  The leaves are difficult to identify because they are extremely variable, so should not be relied upon for identification.  The leaves can be round to oblong in shape and appear as alternate, simple with bluntly toothed margins.  Oriental Bittersweet propagates by seed and produces greenish white flowers in the spring. In the autumn, red berries are enclosed in yellow capsules.  Oriental Bittersweet grows in thickets and can strangle trees and shrubs by entangling their stems.
American Bittersweet (Celastrus scandens L.) is native to Maine.  It is also a climbing deciduous woody vine but is not nearly as aggressive as Oriental Bittersweet.  American Bittersweet produces red berries but they are enclosed in orange capsules and appear only at the terminal ends of the stems, whereas on Oriental Bittersweet, berries and flowers can be found all along the stem at leaf axils.