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Digging in: A bittersweet tale

Oriental bittersweet could become the next buckthorn, if we let it. Here's how to nip a potential invasive in the bud.

May 31, 2011 at 6:57PM
Oriental bittersweet
Oriental bittersweet (Star Tribune/The Minnesota Star Tribune)

Dandelions, crabgrass, Canadian thistle, buckthorn.

There's a long list of exotic plants that have invaded Minnesota and made it their home at the expense of native plants.

Usually, by the time people realize how damaging these plants are, they're so widespread that trying to get rid of them is an exercise in futility. So it's refreshing when a plant is recognized as invasive before it becomes a serious problem. Such is the case with Oriental bittersweet.

Oriental bittersweet is a fast-growing plant usually seen as a climbing vine or, less frequently, as a shrub. Originally from East Asia, it was brought to the United States in the 1860s and widely planted on walls and fences. Because it spread quickly and could tolerate harsh conditions, it was later used to help control erosion along roadsides. It also produces lots of seeds, which are distributed by birds. All of which led to its status as an invasive plant across much of the Eastern and Southern United States.

For years, most experts thought Oriental bittersweet wouldn't be a problem in Minnesota because it wasn't believed to be hardy.

How wrong we were.

Problems sprout up

The Minnesota Department of Transportation reported the first infestations of Oriental bittersweet in 2010. But once those plants were examined, it became clear that this invasive has been in the state much longer.

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Oriental bittersweet is a pest plant because it's so aggressive that it can smother entire plant communities. It also breeds with our native bittersweet, American bittersweet, which could lead to a loss of this less-aggressive plant. And our American bittersweet is a favorite of gardeners because of its bright berries and its strong climbing habit.

The nursery industry has been trying to prevent the spread of Oriental bittersweet by not selling the plant and by developing attractive cultivars of our native bittersweet. If you're thinking of planting an American bittersweet, consider purchasing a cultivar such as Autumn Revolution, Indian Maiden or Indian Brave. All of these cultivars are less likely to be confused with Oriental bittersweet at a nursery.

And if you have any bittersweet in your yard, check to make sure that it's American bittersweet, not Oriental.

Telling them apart

It's not difficult to distinguish Oriental from American bittersweet -- if you know what to look for.

In the fall, Oriental bittersweet has clusters of berries all along the length of its stems, while American bittersweet has clusters of berries only at the ends. But the plants also can be distinguished by their leaves. In spring, the young leaves of American bittersweet are curled as they emerge from buds, while Oriental bittersweet has leaves that are folded over.

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If you find Oriental bittersweet in your yard, you should remove it. Pull out young plants, making sure to remove as much of the root system as possible. Larger plants should be treated with an herbicide. (Look for an herbicide that's advertised as effective against vines and brush and that includes the active ingredients glyphosate or triclopyr.) Be sure to follow label directions.

Oriental bittersweet is not yet considered a major weed in Minnesota. And, if we control it, it may never become one.

Jeff Gillman is an associate professor of horticulture at the University of Minnesota. He also is the author of three books, "How Trees Die," "The Truth About Garden Remedies," and "The Truth About Organic Gardening" (Timber Press, $12.95).

REPORTING A PROBLEM

Monika Chandler, a scientist working with invasive species at the Minnesota Department of Agriculture, has been keeping tabs on Oriental bittersweet since it was found in Minnesota. If you find Oriental bittersweet, contact the agency's "Arrest the Pest" hot line at 651-201-6684.

For more information, go to www.mda.state.mn.us/ and search on Oriental bittersweet.

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about the writer

about the writer

Jeff Gilman, Contributing writer

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