Oriental bittersweet
early fall oriental bittersweet fruits

Invasive bittersweet fruit in early fall in a southeast Michigan park.

Oriental bittersweet growing up tree at Matthaei

It’s easy to spot invasive bittersweet in the fall.

Ripe oriental bittersweet fruits
In farmers markets and shops this time of year you might come across Asian bittersweet (Celastrus orbiculatus) for sale as part of a seasonal decoration. Despite the colorful beauty of Asian bittersweet this is a uniquely noxious invasive woody vine. In this post we take a look at C. orbiculatus along with some ID tips and other details.
Asian bittersweet is native to China, Japan, and Korea. In our neck of the woods it’s found in many different habitats. To complicate matters, its native cousin, American bittersweet (Celastrus scandens) looks similar to orbiculatus but without its aggressive growth rate and size.
C. orbiculatus can grow up a tree to nearly 100 feet, with a “trunk” that may reach a diameter of 5 inches. Its extensive vines smother and strangle by cutting off water and nutrient flow to the tree. In what might be a supreme example of botanical irony, oriental bittersweet has even been observed smothering another invasive plant.
Oriental bittersweet climbing a tree

In a local southeast Michigan park, this invasive bittersweet makes its sinuous advance into the branches of a small tree.

Oriental bittersweet climbing tree
Side by side bittersweet roots-inv and native

A side-by-side comparison of Asian and native bittersweet reveal an important identification clue. Asian bittersweet’s fruits grow in the leaf axils while native bittersweet’s fruits appear only at the ends of branches. 

Native bittersweet fruiting
Just Say No
At farmers markets, Asian bittersweet is sometimes seen in holiday decorations or wreaths that may spread seed when it falls off the wreath outside. Most likely it is C. orbiculatus. If you see it for sale at a farmers market or another location, just say no and gently alert the vendor that they probably have an invasive plant for sale.
To do that with confidence you’ll need a few ID tips. According to the USDA:
  • Asian bittersweet’s fruit and flowers are located in the leaf axils along the length of the stem. American bittersweet has fruit and flowers in terminal clusters.
  • Asian bittersweet has yellow capsules surrounding the fruit, while those of American bittersweet are orange.
  • The pollen of Asian bittersweet is white while that of American bittersweet is yellow.
  • Asian bittersweet’s roots are orange.
How to remove Asian bittersweet? Matthaei-Nichols Natural Areas Manager Steve Parrish says that a very judicious application of an herbicide to the just-cut surfaces of a branch can be one of the most effective eradication techniques. But first, start by pulling or digging up sprouts and seedlings. Mowing may work but most be done regularly, otherwise intermittent mowing may stimulate regrowth. Finally, apply an herbicide only to cut branches as a last resort.
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