Safeguarding Sharon’s forests from bittersweet takeover

SHARON — As a young boy, Tom Zetterstrom remembers his father stopping by the side of the road to pick bittersweet to hang as a decoration at their home. He even crafted a lamp out of the bark of the plant. Sixty years later that son, a conservation expert, is crusading for the extinction of the oriental vine that is wreaking havoc with trees.

Zetterstrom gave a talk to a packed house at Sharon Town Hall Saturday, March 29, on “Defeating Invasive Bittersweet and Reversing Forest Collapse.” This is part of an ongoing series on managing invasives put on by Sharon Land Trust, Sharon Energy and Environment Commission, Sharon Audubon and Sharon Conservation Commission.

The presentation was basically focused on the work that’s been done on Sharon Land Trust’s Hamlin Preserve at 19 Stone House Road. Later that day, there was a guided tree walk and invasive control demonstration at the preserve.

The 180-acre preserve is rich in diversity and aesthetically appealing, said Zetterstrom, who described how he and Roger Liddell of Sharon Land Trust tried to walk the area in September 2022, only to find they were almost immediately engulfed in a sea of invasive bittersweet. “With trees down from the effects of invasives, we were seeing a collapsed forest. This, unfortunately, is a sign of our times.”

With a determination to help clear the area of the harmful perpetrators, a legion of volunteers invaded the property the next spring. One area was not very approachable, so a group of Hotchkiss School students were recruited. Zetterstrom described how the teens cut the vines down to the stubs so that the remainder of the offenders could be treated later. “We made a dent in the problem and declared the site the ‘Hotchkiss Grove.’”

The bottoms of the vines were treated with the chemical glyphosate, which Zetterstrom acknowledged has a controversial reputation. “We’re a little less apprehensive of that chemical than others,” he said. “It bonds to soil particles and doesn’t migrate to water. When put on a cut stem, a year later the vine is gone.”

He then demonstrated using what he called a “blaster” to squeeze the chemical onto a stem. One audience member asked what a blaster is, never having heard the term. “It’s a bingo dauber,” Zetterstrom explained, much to the amusement of those gathered.

Photos of the preserve, from both the ground and Brian Wilcox’s drone shots, showed the audience how it looked when it was first approached and the clear lush meadow now visible.

Early detection is key to eradicating invasives, with the aim of zero growth in order to have a resilient forest. “We’re looking at prevention,” he said. “We want to get it out before it seeds. Seeds can be viable for 12 years.”

While advances in eradication have been made, Zetterstrom was realistic, saying, “We won the battle, but haven’t won the war.” There are aspects of invasives that some people find appealing, such as bittersweet’s red berries. He stressed the need for vigilance, prevention, timing and mapping when dealing with their encroachment. Management plans are highly recommended.

Zetterstrom praised Sharon Land Trust members for their stewardship of the preserve.

The next session is on Saturday, April 5, at 10 a.m. at Sharon Town Hall, when Bethany Sheffer of Sharon Audubon and Mike Nadeau, native landscape expert, will present a talk on invasives and answer questions on plant identification and control.