Round Leaf Bittersweet (Celastrus orbiculatus)

A man puts his hands into a mass of Oriental bittersweet vines covering a shrub.

 
 

Round leaf bittersweet (also known as oriental bittersweet) is a woody vine that can form dense cover and pull down trees. It has been planted as an ornamental vine and the fruits can be spread by birds to new locations.

Description

Appearance

Round leaf bittersweet is a deciduous vine that grows up to 66 feet long. Vines climb by winding around a tree or other support structure.

Leaves and Stem

Leaves vary in shape from oblong to almost round. Leaves alternate on the stem. Leaf size is variable, ranging from 2-5 inches long and 1.4-2 inches wide. Leaf edges have rounded teeth.

Flowers

There are separate male and female plants—only female plants produce fruit. Flowering occurs in the spring and flowers are arranged in clusters of two to seven at the leaf axils. Each flower has five petals and five sepals. Flowers are small and greenish-yellow.

Seeds and Fruit

Fruits are round and change in color from green to bright red with a yellow capsule as they mature. Each fruit contains 3-6 seeds. A typical female plant can produce up to 370 fruits that ripen in the fall.

Rhizomes and Roots

Horizontal stems growing below the soil surface, called rhizomes can send up new plants.

Biology

Round leaf bittersweet is a perennial vine that flowers in May and June. There are separate male and female plants. Birds can eat the fruits and spread the seeds. Seeds germinate in late spring. Plants can also spread vegetatively through underground rhizomes.

Origin and Spread

Round leaf bittersweet is native to eastern Asia. It was brought to the Unites States as an ornamental landscape plant and spread from areas where it was planted. It is widely distributed in the eastern United States. Round leaf bittersweet still has a limited distribution in Minnesota. By detecting Round leaf bittersweet populations early and rapidly treating infestations in Minnesota, we may be able reduce the impact this species has in Minnesota.

Refer to EDDMapS Distribution Maps for current distribution.

Don't be fooled by these look-alikes

Minnesota has a native bittersweet vine, called American (climbing) bittersweet (Celastrus scanden). To distinguish between American and Round leaf bittersweet:

  • American bittersweet has orange capsules around red fruits; Round leaf bittersweet has yellow capsules around red fruits.
  • American bittersweet flowers and fruits are only found at the terminal ends of stems (the tips); Round leaf bittersweet flowers and fruits are found all along the stem at leaf axils.
  • Leaf shape is highly variable in both species and not a good characteristic for distinguishing between American and Round leaf bittersweet.
  • See MDA website for photos comparing the two species.
  • Additional resources for distinguishing American and Round leaf bittersweet:
 
Regulatory Classification

Round leaf bittersweet (Celastrus orbiculatus) is a Minnesota Department of Agriculture Prohibited Noxious Weed on the Control List meaning that efforts must be made to prevent the spread of seeds or other propagating parts. Additionally, no transportation, propagation, or sale is allowed.

Threat to Minnesota
  • Round leaf bittersweet vines can dominate the canopy and shade the understory, reducing and preventing the growth of other plant species. Vines can also girdle trees.
  • At times, the weight of Round leaf bittersweet vines in the canopy can break trees, especially with the additional weight of snow and ice.
  • Round leaf bittersweet outcompetes and displaces the native American bittersweet to the point that Connecticut now lists the formerly common American bittersweet as a species of concern. Additionally, the two species can hybridize but the offspring are generally sterile and unable to further reproduce. By hybridizing with American bittersweet, Round leaf bittersweet causes further loss of American bittersweet populations.
What you should do

Seed could be spread by using fruiting stems in flower arrangements. Avoid using Round leaf bittersweet in flower arrangements.

Round leaf bittersweet is sometimes mistakenly labeled as American bittersweet then sold and planted. Avoid planting Round leaf bittersweet.

One way that invasive plant seeds and fragments can spread is in soil. Sometimes plants are planted purposefully. You can prevent the spread of invasive plants.

PlayCleanGo: Stop Invasive Species in Your Tracks

  • REMOVE plants, animals & mud from boots, gear, pets & vehicles.
  • CLEAN your gear before entering & leaving the recreation site.
  • STAY on designated roads & trails.
  • PLANT non-invasive species.
Native Substitutes
 
Control Methods

Mechanical control can be done for smaller plants. Seedlings can be hand pulled or dug up. Regular, weekly mowing will control Round leaf bittersweet, but less frequent mowing may result in suckering from the roots. For larger plants that have vines extending into trees, cutting would need to be followed by herbicide. Do not try to pull down vines in trees as there is danger that you will pull down heavy plants or branches and injure yourself.

Herbicide control can be done using glyphosate and triclopyr. These are systemic herbicides that are taken up by plants and move within the plant, which can kill leaves, stems, and roots. See the MDA Oriental bittersweet brochure for detailed chemical concentrations and treatment advice.

For woody vines, the vines can be cut and both sides of the cut treated with herbicide. Chemical control options for cut vines include treating the stumps immediately after cutting (within 2 hours) with an herbicide containing triclopyr (Garlon 3A/Vastlan, Garlon 4, or other brush killers with triclopyr) or glyphosate to prevent re-sprouting. Always follow label instructions for herbicides. Herbicides can be applied to cut stumps with a paintbrush, wick applicator such as a dauber or "buckthorn blaster," or a low volume sprayer.

In cases where more than a few plants are treated, add an indicator dye such as Mark-It Blue (dyes are available where pesticides are sold) to the herbicide to mark cut stumps you have sprayed.

For basal stem treatment, a method that applies chemical through the bark, low volume spray applications can be made with Garlon 4 and similar oil-based products. This application method uses triclopyr ester mixed with an oil diluent (i.e. Bark Oil Blue, kerosene) applied directly to the bark of Round leaf bittersweet from the root collar up about 12-18 inches. An ultra-low volume spray wand should be used to minimize herbicide use and reduce the potential for non-target injury.

Disposal

If you need to remove plants from your property, please review the Minnesota Department of Agriculture's Guide to Removal and Disposal of Noxious Weeds in Minnesota contact your local County Agricultural Inspector for disposal suggestions in your county.

Reporting

Report new occurrences by submitting a report through EDDMapS Midwest, emailing Report a Pest, calling Report a Pest (1-888-545-6684), or contacting your local county agricultural inspector.

Resources

Identification and Management

Management

Identification