Oriental bittersweet

Oriental bittersweet is a woody vine that wraps tightly around trees and can smother a canopy. The identification question that matters is whether you have the invasive vine or the native American bittersweet. The answer is in where the flowers and fruit sit, not in the leaf shape alone.

Oriental bittersweet identification

The vine climbs by twining. It has no tendrils and no aerial roots, so it wraps its main stems around a trunk or branch and tightens as it grows. Young stems are smooth and bright green. Older stems have light brown bark with a cracked, fish-netted texture. Climbing stems can reach 60 feet or more.

The leaves are simple, alternate and glossy, rounded to egg-shaped, with finely toothed edges. They turn yellow in fall. The flowers are small, greenish and five-petaled, and they open in late spring. They are easy to miss because they sit in small clusters among the leaves. Male and female flowers grow on separate plants, so only female vines make fruit.

The fruit is the showy part. Yellow or orange capsules split open in fall to reveal a red-orange berry. The fruit stays on the vine into winter, which makes the vine easy to spot after leaf drop. Older plants also have orange roots.

The flower and fruit position test

This is the check that separates the invasive vine from the native one.

The position is more useful than the color. A vine with fruit scattered along the stems is the invasive one. A vine with fruit only in a cluster at the tip of a branch is the native one. If you are unsure, do not cut. American bittersweet is uncommon, and the two species can hybridize.

Oriental bittersweet vs American bittersweet

American bittersweet is native and has many of the same features. Its flowers and fruit grow only at the ends of branches, and its clusters tend to have more than seven fruits. The covering on the fruit is bright red instead of yellow-orange. Penn State Extension says American bittersweet is listed as rare or vulnerable in several states, and that most bittersweet vines found in the wild in Pennsylvania are likely the nonnative species.

The two species hybridize where they grow together. That is another reason to identify before you remove. If you have the native vine, leave it and consider protecting it from the invasive one.

Oriental bittersweet removal

Cutting the vine is usually the first step, but cutting alone rarely kills it. Penn State Extension recommends the window-cut method: cut each vine at the ground and again at eye level. Do not pull the cut vines out of the tree, because that can damage the host. The dead vines will dry and break down over time.

Then treat the regrowth. Wait at least eight weeks after cutting so the new foliage has time to grow. Treat late in the growing season, no earlier than July 1, when the plant is moving carbohydrates down to its roots. Maryland Extension gives midsummer to early fall as the window.

Herbicide options named by the extension sources: triclopyr and glyphosate. Penn State Extension describes foliar sprays on regrowth, basal bark treatment on stems under 6 inches in diameter, hack-and-squirt on stems at least 1 inch in diameter, and cut-stump treatment. Maryland Extension names glyphosate and triclopyr for leaves, bark or a fresh-cut stump. Follow the product label; the label is the law. Check the label for restrictions near water and around desirable plants.

Repeated cutting alone can work only if you keep cutting the resprouts until the root system is exhausted. Penn State Extension says that takes multiple cuttings a year over several growing seasons, and that missing one cutting can let the vine recover. Mowing may encourage root sprouting, so do not expect mowing to control it.

What to do this week

1. Check where the fruit sits. Along the stem means Oriental bittersweet; only at the branch tips means American bittersweet.
2. If it is Oriental bittersweet, cut each vine at the ground and at eye level.
3. Do not pull the cut vines out of the tree.
4. Mark the site and plan to treat the regrowth after at least eight weeks, no earlier than July 1.
5. Bag fruit and cuttings so the seed does not spread.

For disposal, see how to dispose of invasive plants. For methods and timing across species, see the removal hub and the prevention guide. The native vs invasive honeysuckle guide covers another native-versus-invasive vine and shrub decision. State rules are on the Pennsylvania and Virginia pages. More profiles are under invasive plants, and image credits and licenses are on the image credits page.