The Bittersweet Invasion

There may be occasions when Oriental bittersweet (Celastrus orbiculatus) still seems somewhat attractive: perhaps as a single vine with a small flourish of orange and yellow fruit. But modest stature and limited fruit production are what we never see as bittersweet tries, and succeeds, to dominate every habitat it traduces. At this time of year, fruiting or not, there is nothing about the vine that doesn't proclaim its thuggishness, tenacity, and conquest.

In October the waxy leaves turn from an inconspicuous medium green to lime green to bright yellow. There is no mistaking the bittersweet invasion at this time of year. Mature conifers are coiled with the vines to their uppermost branches (see photo); hedgerows of smaller trees that had some individuation in late spring have become enormous yellow caterpillars of roiling, climbing, clinging vines. Trees, fields, outbuildings succumb while the vine has its own genetic license to climb and engulf. It is gardeners (even garden designers like Beatrix Farrand) who have introduced Oriental bittersweet to the wild landscape unable to rally any defense.

American bittersweet (Celastrus scandens) is native from New Brunswick south to Georgia and west to Texas and Wyoming. It is uncommon in Maine, but may inhabit forest edges, rocky slopes and river banks. It can be distinguished by its elongated and serrated leaves compared to the ovate, entire leaves of its cousin from Asia. The flowers and resulting fruit are found at the terminus of the vine, whereas those of Oriental bittersweet are found along small branches originating anywhere on the vine, not just at the tip.

Oriental bittersweet can become an overwhelming problem and if it is on your property, please, don’t throw up your hands and say there’s nothing to be done. We have managed this bittersweet on properties over several years and the results are rewarding.

Ideally, digging up the plant and getting all its roots offers the greatest success, however when plants are established, the roots extend horizontally throughout the ground. And, bittersweet is often growing among trees and shrubs; making it hard to dig.

We suggest a method for the larger vines that focuses on two things: keeping the plants from producing another crop of berries and starving the roots. The fall is a good time to spot climbing vines, with their very particular shade of yellow-green climbing in the trees. If the frost has arrived to your yard and the bittersweet has dropped all the leaves, look for the tangle of berries in the overstory.

We recommend cutting the vines now. Pulling as much of the vine down from the tree or shrub and hauling them to be burned or take them to the dump where they will compacted and taken to the biofuel plant. If that is not easy for you, consider what we are doing at the Native Garden site. We have made a very large pile and covered it with a tarp (see photo) to discourage birds from eating the berries and depositing in places farther away. We will be monitoring this area closely and any new sprouts in subsequent years will be easy to pull.

Sprouts occurring next year from the remaining roots will be closer to the ground, and more manageable. Once you have identified where the vines are, it will be easy to visit these spots during future years’ growing seasons to continue cutting back the plant as often as you can. Each time you snip the plant you are depriving it of its leaves and its ability to photosynthesize and feed its roots. The more you cut over the season, the more you starve the roots. You will also be keeping the vine from producing berries.

When you visit the vines to cut them this fall, look below on the ground for signs of small one and two year plants. (see photo) The leaf color will pop out and you will start to see the many small plants that are quickly establishing themselves. Because they are easy to spot in the fall when other plants are dying back, this is a good time to weed. The leaves on these small plants can be 1/2 inch long, the plant itself as short as an inch, but don’t be fooled by their diminutive character, they will become a beasts!