Data: Bittersweet

You can't talk about invasive plant species in this part of New York State and not talk about Asiatic Bittersweet (AB). This vine is one of the most visible and damaging of the invasive species found in the Hemlock Forest. I know a little more about the specifics of this plant because about 10 years ago it appeared in my backyard. I've been battling it there ever since. I cut it off at the ground and I pull it out by the roots. I've fought AB to a draw in my yard but it is everywhere in the surrounding area; especially in a successional field near my house where it has pulled down several trees by the sheer weight of the vines. AB spreads both by the dispersal of seeds by birds (that eat the berries) and via rhizomes that spread out from every established vine. This plant is not going away anytime soon.

Image One: A dense cluster of Asiatic Bittersweet vines in the Hemlock Forest.

Asiatic Bittersweet is not a shy plant and even in a dense forest spotting the vine is easy. It wraps itself tightly around the trunks of trunks of trees and it will bridge from tree to tree in the canopy. But it is in the late fall and winter that AB really stands out. Mature plants produce large quantities of orange-red berries with yellow sheaths that are quite distinctive. The only plant you might confuse it with is its native cousin, American Bittersweet. Asiatic Bittersweet hybridizes with the native variety and by all accounts the hybrid is quickly replacing the native version everywhere that both species are present. Unfortunately, the hybrids appear to take on the negative characteristics of the invader. Namely, it's ability to produce a mass of vines that tend to strangle whatever it gets a hold of. The native variety is certainly not extinct, so before you take actions to control this plant be sure you know which one you are looking at. The plants are very similar in appearance with one easily spotted distinction. When berries are present, if the berries are found all along the vine it is Asiatic Bittersweet. The berries of the native variety appear only at the very ends of each vine.

AB will be one of the plants I focus on in studying the invasive species present in the Hemlock Forest. The general questions I've discussed in other posts certainly apply and, in the case of AB, there is the additional issue of why the non-native variety is so much more destructive than the native species. In the Hemlock Forest AB is found pretty much everywhere there is an opening in the canopy. There are several old fields in various stages of succession in the forest and AB is present in all of them. It is almost certainly present in other places in the forest as well and one of my first goals will be to map the full extent of its' presence. That data can be used in the future to learn more about how AB disperses. AB can also be used to study how community assemblages are changed by a well established and aggressive invasive species.

Map One: The purple polygons show areas where Asiatic Bittersweet is present in significant quantities. This highly aggressive vine is probably found in other parts of the forest but I have not yet specifically mapped its' presence.


References and Resources:
Asiatic Bittersweet (Wikipedia)
Mistaken Identity: Invasive Plants and their Native Look-alikes