Oriental Bittersweet

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- Oriental bittersweet, Celastrus orbiculatus, is a deciduous, woody, perennial vine.

It was originally introduced in the 1860s from East Asia, and has since become an aggressive invader of natural areas.

It is much more damaging than native vine such as wild grape, Virginia creeper, and poison ivy, which all provide significant habitat for wildlife.

Oriental bittersweet displaces desirable native plants by smothering them with dense foliage, and girdling trees by twining or spiraling around their trunks.

As vines seek out sunlight, they form a layer over the forest canopy.

In some areas, it forms nearly continuous blankets along entire stretches of woodlands.

One of the ways Oriental bittersweet spreads is by seed.

Its conspicuous fruit persists from late summer through winter, and is readily eaten and dispersed by birds.

Established vines also spread by sending up new sprouts from extensive root systems.

One control option is to cut Oriental bittersweet vines and treat the regrowth.

On well-developed vines, most of the leaf area is out of reach of herbicide applications.

Therefore, the first step is to cut the vines.

This kills the strangling aerial portions in the canopy.

Cut vines will shed their leaves and dry so the weight on the host tree will no longer be an issue.

As the vine dies and begins to decompose, the tree is eventually freed from strangling vines that may be wrapped around stems and trunks.

Use the window cut method where the vines are cut at the ground, and again at chest height.

This ensures all vines are located and cut.

It also clears the site at ground level to facilitate follow-up herbicide spraying of resprouts.

Do not pull cut vines from trees.

You could damage the tree while trying to pull the vines down.

Additionally, pulling vines may create a safety hazard from falling branches.

Be sure to flag cut vines as you go.

This will allow you to work more efficiently, as you'll be able to see where you already cut.

The flagging will also allow you to easily locate areas in need of spraying resprouts.

Cutting can be done anytime of year, but is easiest to do during the fall or winter months.

The brilliant lemon lime fall colors make locating the vines easy in autumn.

Cutting is only the first step.

Alone is not an effective means of controlling Oriental bittersweet.

Cut vines will re-sprout vigorously from stumps and roots.

Periodic cutting does help keep vines from strangling desirable trees, but it is nearly impossible to exhaust the plant's root system through repeated cutting.

In fact, mowing has been shown to encourage root sprouting, and may not control the plant even when done periodically.

For long-term control, cutting must be followed with a systemic herbicide treatment applied to foliage.

Treatments applied prior to six weeks of regrowth may not effectively control the roots.

It is recommended that all foliar herbicide treatments to bittersweet vines be applied late in the growing season.

In Pennsylvania, this means no earlier than July 1st.

Mid to late summer herbicide applications enhanced herbicide movement to roots.

Herbicide applications to Oriental bittersweet foliage can be done using a backpack sprayer or a mist blower.

A mixture of the herbicides glyphosate and triclopyr provides more effective control than either active ingredient alone.

This mix is non-selective, meaning it will control other plants it comes in contact with, but with no soil activity, this mix poses no risk to non-target plants to root uptake of herbicide from the soil.

The second option for controlling Oriental bittersweet is to cut and treat the stumps.

Following cutting, you could choose to apply a herbicide to the cut surface of the stumps instead of waiting to treat the resprouting foliage.

This method reduces the amount of regrowth you have to treat, but is not likely to eliminate it entirely.

Cut stump herbicide applications using oil-based herbicides, such as triclopyr ester, can be applied to stumps anytime following cutting.

This mix should treat the cut surface as well as the sides of the stump.

If using water soluble herbicides such as glyphosate or triclopyr, only the freshly cut surface is treated, and the herbicide must be applied immediately following cutting.

A well-development Oriental bittersweet root system may support dozens of stems.

This can make it impractical to treat all the cut surfaces.

It is often less work to simply cut all the vines and wait to treat the regrowth.

The third control option is to treat vines without cutting them.

Herbicide application techniques that target intact stems without cutting include hack-and-squirt and basal bark applications.

They're challenging and often impractical in well-developed infestations, especially where vines are tightly wrapped around desirable trees.

Basal bark applications use a concentrated mixture of the herbicide triclopyr ester mixed in a basal oil.

They effectively treat stems under six inches in basal diameter.

The mixture is applied to the lower 12 to 15 inches of the vine, completely around the stem.

Avoid getting the spray solution on the bark of desirable trees, as it may cause unwanted damage.

Stems one inch in diameter and larger that aren't tightly twined around desirable trees can be treated using the hack-and-squirt method, where a hatchet is used to make downward angle cuts around the stem at a convenient height.

Using a handheld trigger or pump-up sprayer, apply a water-based formulation of triclopyr or glyphosate immediately to the cuts, saturating them but avoiding runoff.

Space the cuts approximately one-inch apart.

To facilitate translocation of herbicide to roots, do not girdle the vines completely.

Of these treatment options, choose the method or combination of methods that is tailored to your specific conditions.

Well-developed vines will require ongoing monitoring to ensure complete control is achieved.

Because Oriental bittersweet seeds are dispersed by birds, new invasions will likely occur.

Continuing monitoring must be a part of any successful Oriental bittersweet control program.