Eradicating Oriental Bittersweet in Southeastern Minnesota

By Celestine Duncan, editor

By Celestine Duncan, editor

Oriental bittersweet is a prohibited noxious weed in Minnesota and targeted for eradication. The noxious weed has been established in Winona County for at least 60 years, Photo by Anne Morse

Oriental bittersweet is a prohibited noxious weed in Minnesota and targeted for eradication. The noxious weed has been established in Winona County for at least 60 years, Photo by Anne Morse

In the hardwood forests of southeastern Minnesota, a group of committed biologists, conservationists and volunteers are tackling oriental bittersweet (Celastrus orbiculatus), an invasive woody vine that alters ecosystems and impacts property values.

Anne Morse, Winona County Sustainability Coordinator and Assistant County Agricultural Inspector, recognized the threat of oriental bittersweet to native hardwood forests and began organizing efforts to contain and control the invasive vine about six years ago.

 “My father was a forester and botanist, so I grew up with a deep love for these woodlands,” says Morse. “Without question, oriental bittersweet is one of our greatest invasive plant challenge. These hardwood forests are extremely valuable ecologically, and for recreation—including hunting, ginseng collecting, hiking, bird-watching, and mountain-biking. Mature oriental bittersweet threatens these values by making woodlands impassable, and vines kill healthy trees by girdling them and smothering the desirable tree canopy.”

Photographs (courtesy of Anne Morse): (L to R) Anne Morse holding stem sections of a 55-year-old oriental bittersweet; oriental bittersweet vine strangling a hardwood tree; and thickets of oriental bittersweet covering native trees

Photographs (courtesy of Anne Morse): (L to R) Anne Morse holding stem sections of a 55-year-old oriental bittersweet; oriental bittersweet vine strangling a hardwood tree; and thickets of oriental bittersweet covering native trees

Root Beer and Bittersweet

A political science major in college, Morse recognizes the importance of empowering the local community and state leaders to tackle oriental bittersweet. “Hiring enough people to cut and treat the vine wasn't possible within the county's budget,” she explains. So instead, Morse has been getting as many people as she can to care about the problem and take action.

To encourage volunteers and engage landowners, Morse sent invitations for a “Root Beer and Bittersweet” event to each landowner within the Mississippi River bluff landscape that’s infested with oriental bittersweet. The local “block-parties” showcase infestations and provide information on impacts, spread, identification, and control of the invasive vine.

 “An important part of our message is educating people not to spread seed by wild-crafting holiday decorations or transplanting the vine in their yard,” explains Morse. “Many of our dense oriental bittersweet infestations are behind homes where people likely discarded holiday wreaths made from the invasive vine”.

 Educating and mobilizing as many people as possible by showing them how the plant spreads and what can happen if oriental bittersweet is not controlled is the goal of the project. “When people see the impact to our forests, we want them to understand they are part of the solution,” Morse says.

The project also needed funding to support the control effort, so Morse and others worked with the legislature to secure special appropriations for invasive plants on the state eradication list. The county received grants for $22,000 in 2018 and $20,000 this year, allowing them to develop an eradication response. “The state agencies have been our unswerving partners in this effort. Without them we simply would not have been able to develop a response,” she says.

Bruce Eng cutting a large oriental bittersweet vine from native hardwood tree. Cut surfaces and stumps are treated with herbicide to kill the invasive vine. Photo by Liza Eng.

Bruce Eng cutting a large oriental bittersweet vine from native hardwood tree. Cut surfaces and stumps are treated with herbicide to kill the invasive vine. Photo by Liza Eng.

Management Strategy

Volunteers play a critical role in the eradication program and help coordinate local management efforts. Bruce and Liza Eng are lead volunteers who became involved in the effort because of their love of hiking in the woodlands.

 “We moved to Winona three years ago and saw that oriental bittersweet had the potential to wipe out our hardwood forests,” explains Bruce Eng. The couple organizes a growing list of volunteers who work about twice a week for two to three hours a day on the eradication effort. “Cutting and treating oriental bittersweet is a very labor-intensive effort, but we do whatever is necessary to carry on the battle against this plant,” says Eng.

Educational programs for landowners are also an important part of the eradication effort. Morse trains landowners on identification and control techniques, so that they in turn involve their family and friends in removing oriental bittersweet on their property and public lands.

“We will be tracking their hours closely this year, and I hope it will show that we successfully engaged them and have a far bigger impact on eradicating oriental bittersweet when combined with efforts of interns and volunteers,” says Morse.

Grant funds are used to purchase tools (saws, quart spray bottles, holsters for carrying bottles) and herbicide (Garlon® 4 Ultra and bark oil) that are provided to trained volunteers and landowners for controlling oriental bittersweet. Eng and county staff store and maintain the equipment.

Oriental bittersweet was successfully removed from more than 120 acres in 2018, and treatment efforts continue. Volunteers, landowners and interns work throughout the year to locate and treat the invasive vine. Mature, seed-producing vines are targeted first to reduce spread. Stems are cut near the ground surface, and cut stumps are treated immediately with a 25% solution of Garlon 4 Ultra mixed in bark oil.

 “It’s important to cut and treat immediately since it’s difficult to relocate cut stems,” explains Morse. “The herbicide treatment is very effective in killing the vine, but we still have to monitor an area for several years, to control plants that we miss.”

Click here for additional information on controlling oriental bittersweet.

Future

Morse and the Engs are optimistic about the eradication effort.

“Building capacity, so that we retain the skills, knowledge, and resources needed to expand the program, is so important,” explains Morse. “The town of Winona has a population of about 25,000, which makes it big enough to have a vision and small enough to implement an intensive management effort against oriental bittersweet.” Bruce Eng agrees. “There is simply not enough money or staff to control current infestations. Our vision is an army of volunteers that continues to grow exponentially in the future.”

 

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