Common Name: Asian Bittersweet or Asiatic Bittersweet or Oriental Bittersweet
Specific Name: Celestrus orbiculatus
Known Occurrence at Taylor Point:
Map Areas: Cliffs 2A, Cliffs 2D, Cliffs 2H, Woodlands 3A, Woodlands 3B, Woodlands 3C, Woodlands 3D, Bridge 4A, Bridge 4B
Category: Invasive, Non-Native, Vine
Ecological Considerations:
Asian Bittersweet is a woody, perennial vine with thin, spindly, silver to reddish brown bark. The vines of this bittersweet twist around the trunks of nearby trees or shrubs and can grow to 100 feet. The leaves are alternate, toothed, and teardrop-shaped to round with a pointed tip. The flowers are small and greenish yellow, with male and female flowers on separate plants. They bloom in early summer and fruit in the fall. The fruit are greenish to yellow and grow in clusters of 3-7 along the stem. In the fall split the fruit open to reveal a bright red inner fruit. A distinctive feature of the plant is the bright orange roots. All parts of the plant are poisonous. Plants are extremely shade tolerant.
Problems Posed by this Plant:
The rapidly growing vines girdles trees and shrubs, cutting off water and nutrients. The vines can smoother vegetation due to excessive shading and the weight of the vines in tall trees can lead to uprooting of trees during storms.
Native Species Affected by this Plant:
Native shrubs and trees are impacted by the rapid growing of this vine by smothering, and girdling of their stems and trunks.
Factors Affording a Competitive Advantage to this Plant:
Asian Bittersweet’s very effective utilization of sunlight to increase plant height provides a competitive advantage over native plants in the surrounding area. It also out competes native plants by forming associations with beneficial arbuscular mycorrhizal fungi (AMF) in the soil that help to colonise the plant roots and aid in the uptake of soil nutrients. It is also extremely shade tolerant.
Propagation Mechanisms and Related Issues Affecting Efforts to Remove and/or Eliminate this Plant from Taylor Point:
Asian Bittersweet reproduces by its seeds being dispersed by birds. Additionally stems can form off of their extensive root structure and small root fragments can regenerate.
Documented Best Removal Practices and Options/Pros and Cons of Various Options:
Small plants are easily hand-pulled if the soils are loose. For larger plants, cut them back in late June or early July, after the plant has put its stored energy into making leaves and flowers. Use a weed wrench to pull them from the ground, bearing in mind that when cut, bittersweet will send up suckers from the roots. Repeat cutting with loppers.
If vines are climbing trees, cut them at about 4 to 5 feet high and again at the ground level to prevent re-spouts form climbing old vines. Weekly mowing will help control runners that can sprout prolifically below or just on the surface of the ground.
Preventing seed production and dispersal and stopping the destructive impacts of climbing vines are primary goals. Early detection and eradication of small populations is essential. Pulling up the plant is effective if all of the roots are removed.
Cutting bittersweet will stimulate resprouting. Mowing is only effective if done weekly when it can deplete the plant’s energy reserves.
Case Studies of Removal Efforts, Lessons Learned and Recommendations:
Additional Photos
Sources cited:
Michigan Department of Natural Resources
Wiki Bittersweet
URI College of Environment and Life Sciences
Suzanne Enser, TPRA CRMC Permit Request Support Paper
Key Words:
Asian Bittersweet
Asiatic Bittersweet
Oriental Bittersweet
Celestrus orbiculatus
Vine