Field Notes—

The Bittersweet Tale Of The Aggressive Vine With Pretty Berries

By Curtiss Clark

For most of the year, there is not much distinction between inside and outside at our house. We throw open windows and doors and bring in flowers from the gardens, shells from the beach, found feathers, and odd specimens of this or that natural curiosity. Field mice and insects don’t wait for an invitation and let themselves in.

But now, with snow on the ground on Thanksgiving morning, there is an urgency to seal the borders with storm doors and weather stripping to keep out the cold. Most of what we bring in from outside these days goes right from the woodpile into the woodstove and fireplaces. The exceptions are evergreen boughs cut from hemlocks, yews, and pines. And bittersweet. Plenty of bittersweet.

It’s been a couple of weeks since Kate and I took pruning shears along on one of our regular walks to clip long vines of Oriental bittersweet. Some of it made its way into a grapevine wreath on the back door and onto the mantel over the fireplace in the living room. A few sprigs were stuck in ginger jars, and the rest lies in a tangle on an old oak table on the back porch awaiting assignment in our emerging holiday décor.

The berries on the bittersweet vines and the sumac bushes are the last vestiges of color in the increasingly monochromatic landscape of winter. The sumac berries are a deep, dark red and will linger as the final glowing ember of October’s flame. Bittersweet berries are a brighter red-orange, and they burst from a bright yellow wrapping, perfect little gifts for the darkening corners of a house. Evidently, lots of people think so. In recent years, we have seen wreath vendors charging a small fortune for a modest coil of bittersweet vines in early December.

Unfortunately, the supply of the pretty berried vines of Oriental bittersweet (Celastrus orbiculatus) is quickly outgrowing demand. Much to the dismay of botanists working hard to preserve New England’s dwindling stock of native plants, there isn’t much that Oriental bittersweet can’t outgrow. It has become, along with purple loosestrife, one of the most dreaded invasive plants in the landscape. It spreads quickly and is difficult to eradicate.

Native to eastern Asia, the Oriental bittersweet was introduced to the United States in the mid 19th Century and has spread throughout most of the eastern states, except Florida. It employs what botanists call a “sit and wait” strategy, establishing itself in untouched closed-canopy forests and woodlands and persevering until the canopy is disturbed, bringing sunlight to the understory. (With so much residential development in this area of Connecticut, there are, unfortunately, plenty of disturbances in the woodland canopy.) Then it grows like Jack’s beanstalk, making up for lost time. It covers over and strangles mature trees, poking more holes in the canopy and overwhelming smaller shrubs and plants below. It can quickly replace a diverse community of plants with a monoculture of vines.

In just the last two years, the median strips of the interstates in this part of Connecticut have developed large patches of it, growing like lesions over old stalwart cedars, sapling maples, and everything in between.

Sadly, Oriental bittersweet has nearly obliterated the indigenous American bittersweet (Celastrus scandens), which is not invasive. American bittersweet has oblate leaves, unlike the nearly round leaves of the orbiculatus, and the berries cluster at the end of the vines rather than throughout. If you have American bittersweet on your property, you are blessed with a truly beautiful native vine. Protect and encourage it.

If you are not so lucky and you cannot resist bringing Oriental bittersweet inside to punctuate the long, cold shadows of winter with fiery red berries, be careful not to abet its attack on our native landscape. When you are done with the vines, let them warm you one last time. Commit them to the woodstove and not to the compost pile.