Invasive Plant Talk: Oriental Bittersweet

Bittersweet is a vine with beautiful reddish orange berries popping out of little yellow jackets, often used to make wreaths and decorations in the fall. There are two species that grow in our area: native bittersweet and Oriental bittersweet. Oriental bittersweet is a menace, responsible for killing trees and pushing its American cousin, as well as other native plants, into near extinction.

Oriental bittersweet (Celastrus orbiculatus), also called Asian bittersweet or Chinese bittersweet, looks almost identical to our native bittersweet, but is easier to grow and blooms more prolifically. That’s the problem: the Oriental bittersweet is taking over and crowding out native plants.

This is an all too common story, similar to the honeysuckle I blogged about last week. Oriental bittersweet vines can grow to over 60 ft. It grows rampantly, climbing over trees, shrubs and whatever else happens to be in its way. The weight of the vines can kill a tree; the thick foliage can prevent sunlight from reaching the leaves or needles. You can often see dead trees covered by heavily twining vines in an area where Oriental bittersweet (or honeysuckle) has invaded.

Because of the abundant berries, grazing birds and animals help Oriental bittersweet to liberally reseed itself. Sometimes birds will even snatch the berries off a wreath hung on an outside door.

It is now illegal to sell or transport Oriental bittersweet in Connecticut, Massachusetts and other states. Although there is a native alternative, there are issues with planting that as well. It is difficult to accurately tell the difference between the native and Oriental bittersweets, and cross-breeding further complicates the identification. In fact, due to these issues, some horticulturalists discourage planting native bittersweet as well as Oriental.

Killing Oriental bittersweet may take repeated applications of herbicide. Start by cutting it close to the ground, then apply glyphosate (one common brand is Roundup) or triclopyr (Brush-B-Gon), according to directions. Repeat the process if (when!) it grows back, until it’s eradicated. Make sure you protect any other plants in the area that you want to survive. You can also dig up the bittersweet, making sure you get as much of the root system as possible.

 I’d like to put in a plug here to hire a licensed professional (such as Almstead) for controlling an invasive plant like Oriental bittersweet. A plant health care specialist has access to different, and often more effective, products than a consumer does. They will also have the equipment and experience to safely mix and apply these controls. Finally, they have the facilities to dispose of unused products and clean their equipment in an environmentally-responsible manner.

One final note: bittersweet wreaths and decorations are illegal in some areas, and condemned by environmentalists. This fall, look for some alternatives like winterberry or juniper.