Invasive bittersweet (Celastrus orbiculatus) is a deciduous woody perennial vine that is native to eastern Asia. It is in the Staff-tree family and may reach 66 ft in length.
Invasive bittersweet invades a great variety of sites including thickets, forests, beaches, roadsides, old fields, and urban areas. It outcompetes trees, shrubs, and other vegetation through climbing and shading. It may also kill trees by girdling them. The seeds are dispersed by water, humans, and animals. Birds and small mammals are attracted to the red inner portion of the fruit and spread the seed after ingesting.
Invasive bittersweet can grow in many different soil types and tolerates a range of soil moistures. It is shade and sun tolerant and can survive and grow slowly in closed-canopy forests until sunlight through disturbance becomes available.
Stems: Occasionally branching, twining, and up to 4 in. wide.
Leaves: Alternate, light green in color (turn yellow in fall), oblong to elliptical shaped (highly variable), 2-5 inches long and 1.4-2.0 inches wide with round, fine toothed margins and a tip that comes to an abrupt sharp point or short taper to a point.
Flowers: Small greenish-yellow flowers with 5 petals that are clustered in leaf axils from May-June.
Fruit: Occurs from July to October. Fruit starts out green in color then turns yellow late in summer with the outer layer splitting into 3 parts revealing bright red fruit inside.
Lookalike: American bittersweet (Celastrus scandens) is native and looks very similar to invasive bittersweet. American bittersweet has more elliptical leaves (twice as long as they are wide), while invasive bittersweet is usually more oval (less than twice as long as wide). This difference must be observed with caution since invasive bittersweet leaves are highly variable. A definitive difference is that invasive bittersweet flowers/fruit are clustered in the leaf axils, while American bittersweet fruits are clustered at the end of the stems. Also, the husk (capsule) of invasive bittersweet fruit is yellow, rather than orange.
Successful management strategies may require a multi-year effort. Always follow chemical label instructions.
Hand-pulling: This method requires the removal of the entire plant including the roots and should be only used for small patches. All climbing vines should be cut at a comfortable height prior to the removal of roots. Cutting at ground level and again at eye height ensures that the plants have been cut while also providing a visual aid to keep track of what has been cut and where treatments can be applied. Attempting to remove vines from trees may cause damage to the host and pose serious safety issues. Cut vines will decompose over time. Plants bearing fruit should be burned or bagged and disposed of in a landfill. Repeat pulling will likely be required since re-sprouting will occur without chemical treatment.
Cut stem treatment: Stems should be cut about 2 inches above the ground and followed immediately by the application of 25% glyphosate or triclopyr solution to the cut stem. Chemical applications are best when applied in the fall when plants naturally draw the chemical to their root system more effectively.
Basal bark treatment: Use a string trimmer or hand saw to remove some of the foliage in a band a few feet from the ground. Apply 20% solution of triclopyr ester in commercially available basal oil with a penetrant to vine stems. Avoid getting herbicide on the host tree.
Foliar treatment: This method should be used for large patches of invasive bittersweet. Apply either 2% solution of triclopyr ester or triclopyr amine mixed in water with a non-ionic surfactant to the leaves. Thoroughly wet the foliage with herbicide, but not to the point of runoff. Foliar applications are best done in the fall when native plants have lost their leaves and target plants will better draw the chemical to their root system.