Bittersweet - The vine that is taking over NH’s landscape

An apple tree now smothered in bittersweet now looks like an elephant, says Dianne Amand. Trees become so covered in the vine it can be difficult to identify them. (Courtesy photo)

By THOMAS P. CALDWELL, LACONIA DAILY SUN

The Lakes Region and, indeed, the whole state of New Hampshire are seeing what Meredith resident Dianne Amand describes as “a silent epidemic” in the form of Oriental Bittersweet (calastrus orbiculatus), a fast-growing, vicacious vine that grows around and eventually strangles its host tree or plant.

Amand said, “Once you learn to identify bittersweet, you will be amazed, perhaps horrified like me, at the extent the plant has spread.”

Malin Clyde, who operates Stewardship Network: New England, said many people do not recognize invasive species like bittersweet when they see it.

“It’s amazing how many people see green and don’t understand one plant from another,” she said.

Stewardship Network: New England is a partnership of 190 organizations representing people who are interested in volunteering for the environment.

“Invasive plants are a fairly hefty component of the projects our partners have,” Clyde said. Two weeks ago, there was a workday at Sewall Woods in Wolfeboro. “The main problem there is oriental bittersweet, and our first line of defense was hand-pulling. It’s amazing how much you can accomplish with 40 volunteers. We made a huge dent in the site and had to move on to a different quadrant.”

With a large party like that, it is much easier to accomplish the task, but for the individual homeowner, it may not be as quick and easy.

“In the most infested areas, like in a forest setting, some people are comfortable using herbicides, and we can put people in touch with the county foresters familiar with herbicide use and who can refer them to professionals who handle herbicides,” she said. “But a lot of landowners aren’t super comfortable with that.”

Aggressive hand-pulling can work if followed up by mowing, she said, noting that pulling bittersweet up by the roots is much easier after a rainstorm.

Forester Andy Fast said invasives are extremely challenging by nature and eradication is not a realistic goal. Instead, he recommends targeting treatment to what can be accomplished.

“I don’t want to discourage mechanical treatment,” Fast said. “There is a role for cutting and hand-pulling, but it’s really hard to greatly reduce and push back that tide of invasion.”

He said strategies depend upon the situation with each property.

“Most natural resource professionals would recommend thinking about what’s trying to be accomplished first,” he said. “In a fully invaded landscape, you could be working on your property and eradicate it there, but if your neighbor is not doing it, it’s a lot of effort that probably will not be tremendously successful in the long term. But if it’s a new localized population, or it’s creeping into a given area, you can target treatment and have a greater opportunity to stem the tide and slow the spread.”

Use of chemicals may be necessary from an efficiency and cost-effectiveness perspective, Fast said.

“It’s important to get recommendations from a licensed pesticide applicator,” Fast said, noting that pesticides are regulated in New Hampshire. “You shouldn’t be using them if it’s not approved for that plant. The folks from the UNH Cooperative Extension can provide those recommendations.”

Dangerous liaisons

A number of invasives are affecting New Hampshire’s forests, Fast said — not just bittersweet and other plants, but also insects and diseases. Most are invasive because they outcompete the native vegetation, and they are especially effective when there is some sort of disturbance, such as a die-off, road expansion, or timber harvest. Invasives respond faster and more effectively than the native vegetation, and a plant like bittersweet can climb to the top of a tree and overtake it.

Bittersweet also is spread by people who are attracted to its red berries and use it for decorations. People make wreaths and other crafts, and the berries fall off and create new seedlings.

“Mostly, it’s birds spreading it,” said Clyde.

“I’m always shocked at the travel corridor between here and Connecticut,” she said. “I thought bittersweet was cold-limited, but we’re just on a slower trajectory. There are already corners of New Hampshire where it’s well-established.”

Amand says the vine is apparent between Meredith and Center Harbor, but also Laconia and New Hampton.

“The vine will engulf trees to the point individual species will be hard to point out, due to the bittersweet vine veil that will be draped over and around them,” Amand said.

She is worried that the trees providing spectacular fall foliage will be strangled out by the vines.

“The plant has taken quite a foothold and the momentum it has picked up will be hard to stop,” Amand said. “As a community, we must address this problem now. Although we cannot eradicate it, we must at least learn to identify bittersweet and show others and weed it out. If we can’t win the war, we must at least try to win the battle.

“Start by going in your own yard, identify it, and rip it out or use chemicals to control the spread,” she said. “Once you learn to identify it, you will not be able to ignore it. The bright leaves make it stand out as a juvenile, and you can’t miss the reaching vines as they creep upward as the plant matures. Once you start pulling it out, its orange root will let you know you are on the right track.”

She said it must be pulled out by the root for permanent removal.

“If large parts of the root are left in the ground, it will grow back,” Amand said.

She also warns not to leave the plants in a compost pile.

“Put the plants in the sun so the roots dry out, then put them in the burn pile,” Amand said.

“There’s no silver bullet,” Fast said. “Whether it’s plants, insects, or diseases, invasives are significantly impacting our woods and forests.”

Clyde said that, although most of the stewardship projects are winding down now, Stewardship Network: New England will be holding an invasive plant workshop at the Squam Lakes Association, 534 Route 3 in Holderness, this Saturday, Nov. 9, with information at http://newengland.stewardshipnetwork.org.

There also is information from the New Hampshire Department of Agriculture Markets and Food at https://www.agriculture.nh.gov/divisions/plant-industry/invasive-plants.htm.

Laconia's 107 Junction sign is barely visible due to bittersweet encroachment. (Courtesy photo)

Wakonda Pond Road in Moultonborough. What kind of trees are these? (Courtesy photo)

A very recognizable bittersweet sprout among some wild strawberries. (Courtesy photo)

Bittersweet vine has covered almost all the trees in this yard on Main Street in Laconia. (Courtesy photo)