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Don't be fooled by its pretty orange berries: Asiatic bittersweet is a nasty invasive

Licensed forester Dave Griswold, in white, removes an invasive Asiatic bittersweet plant with the help of Auburn resident Mary Caron, during a recent workshop on the plant.
Patty Wight
/
Maine Public
Licensed forester Dave Griswold, in white, removes an invasive Asiatic bittersweet plant with the help of Auburn resident Mary Caron, during a recent workshop on the plant.

It's found all around New England, an aggressive climbing vine that grows wildly out of control along roadsides, can topple trees and take over entire woodlots. Asiatic bittersweet (not to be confused with the American variety) snuffs out native trees, shrubs and plants. If there's a vacant building in your neighborhood, chances are the vine has made its mark.

And don't be fooled by its eye-catching, yellow-orange berries in the fall: this plant is one of the worst.

You might call it a "super spreader." I first became aware of it from a Facebook post. Someone shared a photo of the vine's glossy, round, fine-toothed leaves and I realized, not only did I have bittersweet in my yard, but I was seeing it everywhere — on neighborhood walks with my dog and on recent road trips to Massachusetts and New York.

And its bright berries, so popular for making Autumn wreaths? Birds love them, too.

The orange-red berries of Asiatic bittersweet can be eaten by birds, who spread the seeds in their droppings.
Maine Natural Areas Program
/
Maine Department of Agriculture, Conservation and Forestry
The orange-red berries of Asiatic bittersweet can be eaten by birds, who spread the seeds in their droppings.

"Almost every berry that a bird will eat because it's bright orange, they go poop the seed and there's another plant," says Rick Gammon, a horticulturist who runs a landscaping company based in Auburn, Maine.

He says a lack of public awareness is another reason bittersweet is so prolific. Left unchecked, it can climb 60 feet and higher into tree tops and creep across the ground in a monstrous mass, smothering everything in its path.

"People are just not doing anything," Gammon says. "It wouldn't be near as bad as this if people controlled it. There'd be no seed factory. There'd be no producer of the next generation."

So, in some cities like Auburn, they're trying to get after it.

The invasive plant Asiatic bittersweet sends out an aggressive climbing vine that can help it grow wildly out of control along roadsides, topple trees and take over entire woodlots.
Maine Natural Areas Program
/
Maine Department of Agriculture, Conservation and Forestry
The invasive plant Asiatic bittersweet sends out an aggressive climbing vine that can help it grow wildly out of control along roadsides, topple trees and take over entire woodlots.

"If you come over here you can see how it's climbing up the oak tree. It's already cut into it. So, we're gonna try to cut that out," says Dave Griswold, during a recent workshop in a city park, with thunder in the distance.

Griswold, a licensed forester, shows residents how to identify bittersweet, how to pull or dig it out of the ground and use clippers to cut vines at ankle and chest height.

Applying some muscle, Griswold and others work together to yank out this particular culprit and all of its roots.

It's a massive cluster of bittersweet that has wrapped itself around a stand of oak trees. If left alone, the vines would thicken and twist around the trees, strangling them in the process as they climb toward the sun.

"We're not going to solve the problem here, for sure, but we've made some progress anyway," Gammon says.

But getting rid of bittersweet, like so many other invasive plants, takes years of persistence and a combination of methods.

"When we bought our property a year ago there were some vines about the size of my arms that we've had to cut and manage and it just keeps coming back," says Auburn resident Mary Caron.

Caron says she came to the workshop to make sure she's doing everything she can to combat bittersweet. She's already lost some trees that were weakened under the weight of the vines.

"We had some that are just so covered in it that we ended up cutting them down because we didn't want them to fall on our house and didn't want them to fall on our property and such," Caron says.

The leaves of Asiatic bittersweet are rounded with slightly toothed edges, and their fruit appears green before ripening.
Maine Natural Areas Program
/
Maine Department of Agriculture, Conservation and Forestry
The leaves of Asiatic bittersweet are rounded with toothed edges, and their berries appear green in spring.

Caron says she's avoided the use of herbicides which can be applied to freshly cut stalks in the ground, but can harm other native species. And even with mechanical removal methods, bittersweet is still likely to return.

Native to east Asia, the plant was brought here as an ornamental more than a hundred years ago, and is still used in some places. However, it's now considered so severely invasive that its sale has been banned in many New England states, including Maine.

Back in my own yard, horticulturist Rick Gammon gives me the bad news: "I see very well established bittersweet vines growing on your ornamentals — crabapples, cherry, oak — and if left to its own devices, it could kill all of those."

Well, we're not going to let that happen. So, we've worked out a plan that involves intensive pulling and cutting at least a couple of times a year. When it comes to management of invasive plants like bittersweet, Gammon and others say it's all about thinking globally and acting locally — and by all means, spreading the word.

Patty Wight contributed reporting.

Support for Deep Dive: Invasives is provided by Maine Audubon, Friends of Acadia and Coastal Maine Botanical Gardens.

A pile of the invasive plant Asiatic bittersweet that was removed during a recent workshop in Auburn.
Patty Wight
/
Maine Public
A pile of the invasive plant Asiatic bittersweet that was removed during a recent workshop in Auburn.

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