An Asian invasive, more bitter than sweet

Oriental Bittersweet will climb over most other vegetation,
Today's blog post comes from Jordon Tourville, an intern with USFWS at the Rhode Island National Wildlife Refuge Complex. He is interested in invasive plant management and policy as well as hiking around New England.

Today’s blog post comes from Jordon Tourville, an intern with USFWS at the Rhode Island National Wildlife Refuge Complex. He is interested in invasive plant management and policy as well as hiking around New England.

As you drive along the highway this summer you’re probably thinking about a few different things, none of which are probably concerned with invasive plants. While your eyes are focused on the road (hopefully), you may not ever notice the jungle of vegetation growing like a wall on either side of you. Here in southern New England, there is a pretty good chance that a large portion of that sea of green around you is composed of a lovely invasive vine known as oriental bittersweet. Given that this plant is so common throughout the region these days, it might surprise you to learn that it was essentially unknown in the area 100 years ago. Where did it come from? Why is it here? The answers to these questions can be unearthed (no pun intended) with a little historical and ecological digging.

The fruit of Oriental Bittersweet

The fruit of Oriental Bittersweet (Celastrus orbiculatus) turns bright red in September when it ripens. Each fruit contains 3-6 seeds. Seeds are spread by wildlife that eat the fruit as well as by people who use the vines with colorful berries in decorative wreaths. (David Smith, Delaware Wildflowers) 

Oriental Bittersweet is native to eastern Asia, specifically northern China, Korea, and Japan. According to Peter Del Tredici of the Arnold Arboretum, the first recorded shipment of seeds and subsequent cultivation of the vine in the US was in 1879, when a certain Samuel Parsons sent them to the Arnold Arboretum outside Boston. Parsons procured these seeds from a man named Thomas Hogg Jr., an industrious person also responsible for the introduction of kudzu and other well-known invasive plants from Japan. These plants were so successful in the Arboretum, that after 10 years of cultivation they were up for sale at Kissena Nurseries in Flushing, New York.

Horticulturists were amazed by how many fruit the vine produced and how gorgeous the plant appeared in the fall. Due to its growing popularity as an ornamental, the next 30 years were characterized by rapid expansion of the plant into new markets. It was grown in the New York Botanical Garden, sold in nurseries in New England and as far south as Ashville, North Carolina, and planted as an ornamental and a hedge plant in countless gardens. In later years, several states (including Rhode Island) suggested that oriental bittersweet be used as a highway bank planting.

The most reliable way to identify Oriental bittersweet from the much rarer American bittersweet is by their fruit

The most reliable way to identify Oriental bittersweet from the much rarer American bittersweet is by their fruit. The Oriental bittersweet has clusters of 1-3 fruits attached at leaf axils along the stems. The fruit of American bittersweet is found only at the tip of the stem. (Monika Chandler, Minnesota Department of Agriculture)

While several individuals and papers urged caution in promoting this vine, it wasn’t until 1973, when an article entitled “Distribution of Oriental Bittersweet in the United States” by David Patterson, did the threats posed by Oriental Bittersweet really become acknowledged. Unfortunately, bittersweet had already long since escaped cultivation and today grows at thousands of sites in 25 states.

The next time you drive down the highway and you happen to glance at the side of the road, you might be shocked by the amount of oriental bittersweet you see that you never noticed before. You will see the bright green leaves all stemming from twisted green stalks. The US Fish and Wildlife service is making an effort to stem the tide and minimize the impact of this particular invasive, but any help is appreciated. If you find this vine growing around your house you can always cut or mow it at its base to help slow its growth and reproduction. It is very tenacious so multiple treatments will be necessary, but be persistent. With enough effort, maybe we can one day stop worrying about these invasive vines and go back to thinking about a nice drive to the beach.

Oriental Bittersweet will climb over most other vegetation,

Oriental Bittersweet will climb over most other vegetation, and will appear as a tangled mass of vines and leaves when passing it on the road in the summer. (Jordon Tourville/USFWS)

 

 

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