Invasive bittersweet (Celastrus orbiculatus) is a woody, perennial vine that can climb up to 60 feet using plants or structures. Leaves alternate on each side of the vine and are oval in shape. The fruits are yellow-orange berries that emerge from an outer shell and can persist over winter. The vines often climb on shrubs or strangle trees by coiling tightly around their trunk.
There is also a species of bittersweet that is native to Michigan called American bittersweet. One of the main differences between invasive bittersweet and the native species is that the native species has clustered berries at the end of the stem and invasive species has berries spread along the stem. Check out this guide from USGS to learn more about their differences [PDF of Guide]
Invasive bittersweet overtakes native trees and shrubs and can girdle trunks. As the vines mature, they weigh down the tree canopy and can break branches or uproot trees. To prevent this, cut the vines at their base. The plant will still be alive, but all the biomass about the cut will die and eventually fall down. Another important thing to note is that this species spreads easily because birds and other wildlife eat the berries and disperse their seeds.
There are multiple treatment options for invasive bittersweet. These include both chemical and non-chemical options.
Non-chemical control methods:
- hand-pulling seedlings: small seedlings can be uprooted by hand. They should be placed in an area where they will not re-sprout, or in the garbage.
- cutting: bittersweet vines can be cut near the ground to kill any vegetation above the cut. Cut vines will take some time to fall down from the trees on their own. Note: this method will not kill below any of the plant below the cut, and it can regrow.
Chemical control methods:
- foliar spray: herbicide is sprayed onto the foliage of the plant. This is the most common method used to treat large patches, often done by contractors. Note: keep in mind that bittersweet grows on trees and herbicides used can often affect the trees if they are sprayed as well.
- cut-stump treatment: herbicide is applied to the outer rings of a cut stump within a few minutes of making the cut. Note: should not be done in spring, as herbicide will be pushed out of the plant and have little to no effect.
- basal bark: herbicide is applied with an oil carrier to the entire circumference of the lower 15 inches of bark. Note: should not be done in spring, as herbicide will be pushed out of the plant and have little to no effect.