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Ann Wessel, St. Cloud Times, Published October 28 2013

Bittersweet a beautiful but bothersome plant

ST. CLOUD, Minn. – An invasive plant that agriculture and forestry professionals describe as worse than buckthorn is establishing itself in Minnesota – in one case planted because nursery stock was mislabeled, taking root elsewhere when flower arrangements were tossed.

Bittersweet is a potential door-brightener, often collected, sometimes woven into wreaths or tucked into fall floral arrangements. The native species, American bittersweet, produces orange fruits and capsules on a contained vine. The invasive version is a potential forest-killer, often spreading unnoticed while it smothers everything in its path.

“Wherever it’s going to move into a native woodland it could take out all of the understory species and it could take down the overstory species,” said Susan Burks, the Minnesota Department of Natural Resources’ forestry invasive species program coordinator.

“You could end up with nothing but bittersweet growing over the skeletons of the other plants.”

Discovered in the U.S. in the late 1880s, Oriental bittersweet produces orange fruits and yellow capsules on a vine that can put down roots wherever it touches the ground. It was first noticed in Minnesota in 2011, where it had been planted from bareroot nursery stock in an Anoka County right of way.

A 30-year-old colony was later discovered in Winona. Other large infestations emerged in Red Wing and Stillwater.

“I think it’s the worst invasive plant I have ever worked with. It’s so destructive because what it does is it climbs up the tree, and the vine weight alone is heavy. But then if it’s compounded with snow and ice and maybe high wind, the trees just break,” said Monika Chandler, invasive species specialist with the Minnesota Department of Agriculture.

Because the cheery fruits are so pervasive in fall floral arrangements, this is a good time of year to watch for it.

“I think the most important thing for people to understand is something that looks as innocent as a floraculture arrangement can really cause enormous problems,” Chandler said.

Tossed wreaths can take root. Birds can eat the fruits and spread the vines, which can reach 66 feet long, according to the Minnesota Department of Natural Resources. They can root in a mass of ground cover, climb trees and smother the leaves.

“In terms of how it behaves, it’s like the kudzu of the North because it covers everything and weighs it down,” said Susan Burks, St. Paul-based forestry invasive species program coordinator with the DNR. “It’s worse than buckthorn. Buckthorn only gets to be a small tree. It doesn’t get up into the canopies. It doesn’t get up to the top and wrap around the other plants.”

While the known state infestations are small, Burks said they are difficult to treat because of how easily they grow and spread. Simply cutting the vine and brushing the stump with herbicide – a common buckthorn treatment – doesn’t always work because both ends of the plant must be treated.

Dead vines are left in place because removing them is cost-prohibitive and would damage remaining trees.

In states such as Connecticut and Massachusetts, Chandler said American bittersweet may go extinct because it’s being out-competed. While the native bittersweet accepts pollen from the invasive, the reverse is not true. Hybrids usually don’t survive.