Tag Archives: Oriental Bittersweet

THIS WEEK IN STEWARDSHIP: Battling Oriental Bittersweet

The stewardship crew has been busy managing more invasive woody shrubs along the Paint Creek Trail and at Bear Creek Nature Park. One invasive woody shrub species we would like to highlight is oriental bittersweet (Celastrus orbiculatus). Bittersweet can be found in a wide range of habitats from woodlands to marshes. It’s a woody vine that will wrap around other plants and trees, covering the vegetation completely and killing them in the process. The twining stems can even climb up to the top of mature trees!

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Oriental bittersweet climbs anything it can. The weight of its heavy vines can take down mature trees and smother ground vegetation.

One way to identify bittersweet is by its extensive, bright orange roots. The leaves are alternate along the stem (not in pairs), with toothed margins. The leaves often have a roundish body that tapers to a long tip, but can vary in shape. Its flowers are a pale greenish-yellow and can be found at the base of the leaves along the stem. Bittersweet produces small orange fruits, which makes the vines popular in holiday wreathes.

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Ripe bittersweet fruits are attractive with their orange and red contrast, but don’t be fooled! Bittersweet will take over if you throw your holiday wreath in the woods. Photo by iNaturalist user Ganeish, used with permission CC-BY-NC.

This aggressive invasive species can produce large populations from just one seed! Small root fragments can also regenerate, making it difficult to remove completely. Birds and small mammals enjoy the fruits and help this invasive species travel long distances – however the fruits are poisonous to humans and livestock. Don’t spread bittersweet with your holiday wreath!

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So if you see the crew out in the parks and would like to learn more about bittersweet and how to identify it, please stop to ask questions!

Beware of a Beautiful Killer! Appearing Now on a Tree Near You!

Bittersweet killing young red maple
Asian Bittersweet killing a young Red Oak

Lovely and lethal.  That’s the sad truth about Asian Bittersweet (Celastrus orbiculatus).  Every fall people fall in love with this aggressive, invasive vine that chokes the life out of trees and bushes.

In the autumn, the vine is seductively beautiful.  Bittersweet produces seed casings that, in the fall, look like bright yellow berries that crack open to show the red fruit inside.bittersweet

People are tempted to pick them for fall wreaths and some people plant them in their gardens, thinking that the berries will provide food for the birds.  And indeed, that’s a major way that this killer spreads!

This aggressively invasive vine wraps itself around and through trees and shrubs and chokes them to death! In its search for sunlight oriental bittersweet climbs to the top of the tree, squeezing it tightly and choking off its access to light and nutrients. Bittersweet can get so heavy in the crowns of trees that they are more vulnerable to falling in wind storms. It also shades out plants below, killing them as well. By killing mature trees and preventing new trees from growing, bittersweet can turn a  healthy forest into a bittersweet monoculture.

Dr. Ben VanderWeide, Oakland Township’s Natural Areas Stewardship Manager, works to keep this killer plant under control, but it still crops up in our parks.  So please, don’t pick this plant and thereby spread its seed more!  Don’t use it for decorations, especially out of doors where birds can eat the seeds and where you could drop seeds on the ground.

If you already have this plant on your property, it would be wise to get rid of it!  The video below from University of Minnesota Extension gives great information about how to do that.  Here are a couple of quick hints:

  • Don’t try to pull the vine from the trees; you’ll only spread the seeds. The thick and heavy vines, or the tree itself, could fall down on you!
  • It’s best to cut the vine and then immediately treat the stump with an herbicide.  But choose your herbicide carefully and don’t let it touch your other plants, especially native ones! Always read and follow the herbicide label.
  • For landscaping, use native fruit bearing plants that birds can enjoy, like Nannyberry (Viburnum lentago), Serviceberry (Amerlanchier interior), Flowering Dogwood (Cornus florida), Eastern Red Cedar (Juniperus virginiana) and other listed by the Cornell Ornithology Lab as good for birds.

Here’s the video from the University of Minnesota extension on why and how to rid your property of Asian Bittersweet:

If after you’ve watched the video, you still have questions or would like to help control this plant in our parks, call Dr. Ben VanderWeide at the Parks and Recreation Commission for more information.