Asiatic (Oriental) Bittersweet AKA Python Vine or Round-leaved Bittersweet is a monster. This woody vine is an east Asia native that has been in the U.S. since about the Civil War. But, like so many of our 100 or so (and counting) invasive exotic plant species, there was considerable lag time between introduction, naturalization and becoming a widespread ecological problem. Python Vine became an issue in the northeast states first but its monsterous behavior is now on display throughout the Midwest. Celastrus orbicularis (its scientific name) is very similar to our native bittersweet (C. scandens). Both species are usually dioecious (separate male and female plants) but occasionally the plants are monoecious, sometimes even with perfect flowers (i.e., both male and female parts in the same flower). Both species are shade tolerant and frequently hybridize to produce indistinguishable offspring. The main differences between the separate species are the roots, fruits and bark. All parts of both species are poisonous.
A large part of the invasive problem stems from the fact that when in fruit the exotic, like the native, is very appealing. Branches with pretty open fruit gathered for ornamental display is a main means of spread. But do not let its attractiveness in autumn fool you. The moniker Python Vine is well deserved. The stems, which can exceed 5-inches in diameter, are capable of climbing the tallest trees. The additional weight of the rampant vine can result in branches and whole trees falling. Moreover, the encircling vines become woody and literally wrap around the host in an ascending counterclockwise fashion.. The bark of young stems is smooth but older and thicker stems resemble a coarsely scaled serpent. I have witnessed wild grape and black locust, themselves both thuggish species, be squeezed to contortion and death -- girdling its host. When I first saw this constriction, I remember saying WOW! The above pic is Python Vine wrapping around a 6-inch diameter black locust. Most of the foreground leaves and stems also belong to the vine.
Python Vine has reddish roots, a tendency to grow at an angle out of the ground, and the new growth has tapered leaf tips rather than the more round leaves found on older stems. The enticing clustered capsules -- yellow orange case with red seeds -- are produced axillary along the stem rather than at the apex which is characteristic for the native lookalike. Python Vine is fecund and not picky regarding water or substrate. Remove it ASAP. FYI Python Vine belongs to the same family (Celastraceae) as the horrendous wintercreeper and burning bush. I recommend nothing in the family for ornamental use on your property.