Image credit: Ansel Oommen, Woody Invasives of the Great Lakes (WiGL) Collaborative
Round Leaf Bittersweet
Brought from Asia in the 1860s as an ornamental plant, round leaf bittersweet is a
perennial in the Celastraceae family. It is an invasive woody vine that inhabits suitable
areas where it can find a host, commonly in undisturbed forests where it clings to
other woody plants and on roadsides where it climbs fences.
The vine can reach lengths of 98.5 ft and reach a diameter of 7 inches.
Stems are light brown, often with noticeable lenticels, and have a solid white pith
Leaves are 2-5 inches long, rounded, alternate, finely toothed, and glossy.
Flowers appear in small, green-yellow clusters with five petals and blooms from May
Fruits are green in the summer months, ripening into a yellow-orange color in the
fall. These fruits remain on the vine throughout the winter
While round leaf bittersweet may look similar to its native counterpart, American
bittersweet (Celastrus scandens), some key differences for identification are found in the leaves and fruits of the
two species. In round leaf bittersweet, the leaves and fruits grow along the stem
of the vine on the leaf axil. Whereas the American bittersweet leaves and fruit only
grows in terminal clusters on the ends of the stem. There is notably a chance of hybridization
between the two species, which can make identification more difficult.
KISMA Management Practices
One large patch of round leaf bittersweet that has been managed by KISMA was treated
with a combination of manual and chemical management practices. First, the KISMA crew
dug up the patch, removing as much of the root mass as possible. Dug up plants were
then burned. Lastly, all resprouts were chemically spot-treated by the Forest Service.
Note: Round leaf bittersweet is able to hybridize with American bittersweet and impact
host species by reducing photosynthesis and girdling trees makes it a KISMA species
of concern. Report any instances of round leaf bittersweet found in natural habitats
to KISMA. Currently, we are focusing on building a better understanding of where this
invasive vine occurs throughout the Keweenaw.
Both woodbine (Parthenocissus inserta) and Virginia creeper (Parthenocissus quinquefolia) make excellent alternatives for round leaf bittersweet as they are native to the
Great Lakes region. Importantly, American bittersweet should be avoided as a native
alternative as nurseries can easily confuse it with round leaf bittersweet.