Oriental Bittersweet: Accurate Identification

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- Oriental bittersweet is an invasive woody deciduous perennial vine.

Originating from East Asia, it was introduced and marketed for ornamental use in the United States starting in the mid-1800s.

It has since naturalized and become an extremely aggressive and damaging invader of natural areas.

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

Oriental bittersweet chokes out desirable native vegetation by smothering them with its dense foliage and by strangling stems and trunks with its twining vines.

Oriental bittersweet can be found growing in forests, meadows, roadsides, and fence lines.

It prefers full sun, but tolerates dense shade when young.

Sprouts growing in dense shade seek out full sun by climbing nearby vegetation and forming a blanket over the forest canopy.

It thrives especially well in moist locations in areas with exposed mineral soil, such as disturbed sites, but will grow in many soil conditions, including sand dunes and bogs.

The three to four-inch-long leaves are distinctly round, with tooth margins or edges, with leaves on new growth often having pointed tips.

They are alternately arranged along the stem.

In autumn, the leaves turn a vivid yellow, usually before the native plants gain their fall color, making the vines easy to spot from a distance.

Oriental bittersweet is diecious, meaning the pollen and fruit are born on separate male and female plants.

Female vines have flowers that appear in late spring in clusters of two or three at the base of each leaf all along the stem.

They are less than 1/2 inch long and yellow-green in color.

The male flowers are not distinct.

The yellow-skinned fruit first appear on female plants in late summer.

In fall, the yellow skin splits to reveal a bright red center.

The fruit is retained on the stem through winter.

The conspicuous combination of yellow and red make Oriental bittersweet simple to identify, even after leaf drop.

Young growth on Oriental bittersweet vines is bright green and flexible.

Large woody stems have red-brown bark that has a cracked, fishnetted texture.

Oriental bittersweet climbs by twining or winding itself around host plants.

It does not have tendrils, barbs, or aerial rootlets to assist in climbing.

Single vines can reach 60 feet in length, though they only grow as high as the vegetation they climb.

As a perennial vine, it puts on annual growth and can reach diameters of over 10 inches.

The native lookalike, American bittersweet, is far less common than the invasive Oriental bittersweet and is listed as rare or vulnerable in several states.

American bittersweet leaves are more football-shaped than rounded.

Their flowers and fruit also emerge only from the ends of the stems rather than at each leaf axle as with Oriental bittersweet.

The fruit of American bittersweet also has a bright red covering instead of yellow.

Oriental bittersweet reproduces by seeds and vegetatively by sprouting from an extensive root system.

Root sprouting is especially vigorous after the vine or roots are cut or damaged.

Vegetative reproduction can result in large patches of bittersweet.

Birds and other wildlife readily consume the large numbers of berries, spreading the seeds far and wide.

Humans continue to be a significant vector in the spread of Oriental bittersweet due to its continued use in arts and crafts projects, such as decorative wreaths and other dried arrangements.

Its seeds remain viable even after drying and can germinate once the wreath is discarded.

To summarize, Oriental bittersweet is an aggressive woody perennial twining vine with alternately arranged leaves, yellow-skinned red fruit that appear on female vines, and red-brown bark that has a cracked, fishnetted texture.

By using these key characteristics, you'll be able to properly identify Oriental bittersweet on your property as well as across the landscape.

This is the first step in any invasive plant control program.