ASIATIC BITTERSWEET
Celastrus orbiculatus

Name and Family
History
Identification Guide
Impacts
Management
Reporting
Image Gallery
References

Name and Family

Asiatic bittersweet, Celastrus orbiculatus, is a member of the staff-tree or bittersweet family (Celastraceae). Asiatic bittersweet is formerly known as Oriental bittersweet.

History

Asiatic bittersweet is native to China, Japan and Korea. It was introduced into North America around 1860 as an ornamental plant. Around Christmas, the vines and bright red berries are often used to make wreaths and other dried plant arrangements, which can promote the plant’s spread. The vines have also been used in basketmaking and in traditional ropemaking. Although poisonous to people, bittersweet fruit is eaten by many birds and small mammals, for whom it is a nutritious food source, especially when eaten in late winter. The seeds are often retained in bird’s digestive systems for a long time, promoting long-distance dispersal from the parent plant (reports indicate seed persistence in the gut over several weeks in some cases).

Identification Guide

Here are some features that may help you identify Asiatic bittersweet:

Extremely shade tolerant.
All parts of the plant are poisonous.
Perennial woody vine capable of climbing up surrounding vegetation to 18m high. Usually dioecious (male and female flowers are found on separate plants) but sometimes, the plant can have perfect flowers. This means that ta single plant produces both male and female reproductive structures and can self-pollinate.
Flowers: Small, five-petaled, pale yellowish-green with white centers, found growing in clusters along the leaf axils.
Fruit: Produces bright red berries that begin their growth as small green fruit with a short stem-like feature at the end where the flower once grew. As the fruit matures, the berry will enlarge, and its outer capsule turns from green to yellow. In late summer and early fall, the capsule will dry and split apart, revealing the mature red berry within. Capsules split open in three parts (each with a central ridge), and the berries within are also split into three sections. Berries persist into the winter after the leaves die back (on female plants).
Leaves: Leaves are alternately arranged, roundish to teardrop-shaped, with finely toothed edges. The shape can be quite variable even on the same plant.
Stem: Twigs are light brown and have distinct round leaf scars when leaves fall off for the winter. Older stems are silvery brown, and the trunk is often finely scaly.
Root: Deep and extensive root system. Roots are orange and run horizontally over large distances, sending up sprouts. This lateral spread is seen even in young plants.
Habitat: Broad habitat suitability. On PEI, it is often found in roadsides, hedgerows, woodlands, forest edges, and meadows.
Lookalike: American bittersweet, Celastrus scandens. looks similar but the flowers & berries grow in different places along the stem; Asiatic bittersweet’s grow along the leaf axil whereas the American bittersweet has them growing in clusters at the terminal end of the branch. NOTE: American bittersweet is not known to grow on PEI, and any populations found should also be reported to the PEIISC.
Reproduction: Spreads by seed and vegetatively by laterally spreading underground roots that form new stems. The seed bank is short lived. Studies show that most seeds established after the first year, and the two years following had no appreciable germination. The plant reaches maturity and can begin producing seeds at 2 years of age.

Impacts

As a vine, Asiatic bittersweet depends on the support of other plants and structures to climb, as it cannot support itself for upright growth. This dependance impacts the plants Asiatic bittersweet climbs on, competing with its support plant for light, space, and nutrients. Over time, Asiatic bittersweet’s squeezing action as it wraps around another plant can completely cut off the flow of water and nutrients in the plant being climbed. Asiatic bittersweet also adds weight and wind resistance, making the climbed plant’s limbs susceptible to breaking and the entire plant susceptible to falling down. Asiatic bittersweet grows at a very high rate and can easily outcompete many native species.

Management

Caution: Vines are often attached to dead or weakened branches that could fall down and injure those nearby if shaken or disturbed. Do not tug on vines. Instead, sever the plant’s connection to the roots and leave the aboveground material in place. Over time this material will likely dry and fall off on its own. Care must be taken when walking while managing this plant as the likelihood of tripping on vines is high.
Management timing: Preventing seed dispersal is important in stopping the spread of this species. Ideally management will have begun before berries have formed. Formation occurs in August – November, and berries often persist on branches until February. Female plants with berries will be easy to identify from November to February as many other plants will have died back and the red berries will be obvious against the white snow. Marking these plants for future management is recommended.
Small Infestations:
- i. Hand Pulling up root systems can be effective. Cut the vine at eye level and follow the stem downwards to the root system (which spreads outward horizontally) and hand pull gently so that all the root fragments are removed. If root fragments are left behind, the plant will usually resprout. Do not try and untangle the part above eye level, this can be left on the tree and will loosen overtime, pulling is hazardous.
- ii. Tarping can be effective. Cut the vine at eye level and again at ground level then tarp entire area occupied by the root system, which can extend further than you may think. If you are unsure as to how far to tarp, follow a few outer roots to get a better idea.
- iii. If it is too late in the season to pull roots or tarp due to snow, the fruit can still be removed from the plant to prevent further spread. Take the time to mark this plant for future management.
Large Infestations:
- i. Must be tackled using a combination of methods. The PEIISC recognizes that herbicides can be effective in managing this plant on a large scale but does not offer chemical control advice at this time. If the need arises, we remind all land managers to follow provincial and federal regulations as well as manufacturer’s directions on the product labels.
- ii. Although cutting the plant will temporarily protect trees it is not a permanent solution, the roots will resprout from any remaining stumps and roots. Repeated cutting over many growing seasons is required to control Asiatic bittersweet. If it is not done consistently, it is likely to increase the population’s size.
- iii. If it is too late in the season to pull roots or tarp due to snow, the fruit can still be removed from the plant to prevent further spread. Take the time to mark this plant for future management.

Reporting

Quick reporting and swift action to invasive species establishment is key to a successful response.
If you have seen, or suspect you have seen, Asiatic bittersweet on PEI, report your findings to the PEIISC.
Include the location of your find, your contact information, the date you found the invasive species, and photos of your observation.
PEIISC staff will review your report, confirm the identity of the plant, and if necessary, provide instructions on how to proceed.
Ensure you do not remove any Asiatic bittersweet from the area by cleaning equipment and removing all plant parts from your footwear, clothing, and bags before leaving the site.
Reporting methods:
- Send reporting information to peiinvasvies@gmail.com.
- Make your report through iNaturalist, either on www.inaturalist.ca or the iNaturalist app.
- Contact the PEIISC via Facebook or Instagram.