Knocking out knotweed

Groups mount eradication efforts parkwide

By Carolyn Shapiro

Doug Johnson remembers noticing Japanese knotweed for the first time about 15 years ago in southern Vermont, where his wife’s parents own an old farmhouse.

He didn’t recognize the plant, so he looked it up and learned of its invasive behavior. Johnson wondered whether it was in the Adirondacks around his second home, on Seventh Lake in the town of Inlet.

It was. But it wasn’t yet as far gone. Johnson saw an opportunity to get rid of the aggressive knotweed before it infested the town and squeezed out the native plants where it colonized in byways and waterways.

“I really hadn’t been aware of it in the Adirondacks until I started looking,” said Johnson, who lives in Springfield, Mass. He “started seeing a lot of it. Inlet was being overtaken.”

Johnson, a physician specializing in pulmonary and sleep medicine, grew so concerned about knotweed that he earned his New York State certification as a pesticide applicator so he could inject the plants with an herbicide that kills them. He also founded the Regional Inlet Invasive Plant Program to help locate knotweed clumps and eradicate them on public and private property.

“I’ve been going there basically every year of my life and really want to preserve what I like about the Adirondacks,” he said. “What I saw knotweed doing to southern Vermont, if that happened to the Adirondacks, it would really change the character.”

As invasives go, knotweed stands high on the list of bad actors identified by the Adirondack Park Invasive Plant Program, part of The Nature Conservancy. APIPP joins Japanese knotweed with giant knotweed and bohemian knotweed in the same related group—all similarly problematic.

APIPP classifies invasive species in four tiers. Knotweed falls in Tier 4, the most serious one, which means it has grown so dense and proliferated to the extent that it no longer qualifies for eradication or containment. It’s everywhere. APIPP can only try to suppress it, to mitigate damage to sensitive areas or prevent encroachment that threatens public safety.

And knotweed is determined. Almost any broken root or stem will regrow. Someone who rips it from a backyard or pulls it along the highway will only introduce knotweed to a new area wherever that debris is dropped. 

“A part as small as a centimeter, as long as it has one of those nodes on it, can become a new plant,” Bernacki said. “So not only do you have that erosion happening, in that streambank, all that flooding will break up the knotweed, and you just get infestation spread down the river.”

On top of that—or below it, actually—a non-native species of earthworm has shown up to eat the Japanese knotweed leaves that drop and decompose, said Bernd Blossey, a professor of national resources and the environment at Cornell University and an expert in invasive species. The earthworm poop runs off into the water with the increased erosion from the knotweed. That creates sediment in the river bottom, which cuts off oxygen to fish.

“We’ve brought these things here; they’re having an impact on our environment,” Bernacki said. “That’s not just, ‘They’re not pretty to look at and they make it hard to get to the stream.’ The stream washes out, they change the habitat and dynamics and structures of these ecosystems.”

APIPP is one of eight Partnerships for Regional Invasive Species Management that work under management contracts with the state Department of Environmental Conservation. Since its founding in 1998, APIPP has battled common buckthorn, tree of heaven, the hemlock woolly adelgid and zebra mussels, among others.

The most effective removal method for knotweed is a common herbicide called glyphosate that is injected with a syringe into the cane of the plant, which absorbs the poison and carries it to the roots. Bernacki’s crew of four, led by a certified pesticide applicator, also uses a foliar spray from a backpack for larger infestations.

“Those methods are very exacting,” she said. “We don’t want to impact those native plants that are growing nearby because we want to recolonize the area after the knotweed’s gone.”

APIPP began tracking knotweed in 2012. As of the end of 2021, it had mapped 1,373 infestations–including 92 new locations figures that suggest a growing presence.

Knotweed originated in East Asia—likely Japan, China and Korea—and belongs to the buckwheat family of plants. People compare its tubular, jointed stems to bamboo, but it’s unrelated.

Knotweed arrived in New York and the Adirondacks, and elsewhere in the United States, in the late 1800s. Many people liked its heart-shaped leaves and fronds of white flowers and planted it. Garden centers and nurseries carried it.

“We were not aware of it being an invasive, non-native plant,” said Ellen Collins, a Blue Mountain Lake resident since 1967. “A lot of it was in backyards, kind of out of public view.”

Collins said she found knotweed on the property of The Hedges at Blue Mountain Lake, a famous summer resort that her husband’s family once ran. “My husband thought probably his grandparents planted it in certain places at The Hedges because it created a barrier in front of the kitchen area,” she said.

In 2008, a mutual friend introduced Collins to Johnson, who alerted her to the evils of knotweed, she said. She joined him in his quest to beat back the plant and recruited others.

During budget discussions in the town of Indian Lake, which includes Blue Mountain Lake, she has asked for funds to pay for knotweed treatment. From fellow members of the Indian Lake Garden Club and the Blue Mountain Lake Association, she has solicited donations.

In 2020, APIPP took over the Regional Inlet Invasive Plant Program that Johnson had expanded to other knotweed-plagued areas of the park. APIPP provides limited resources and assistance to that program, now known as the Knotweed Management Partnership. It helped treat 117 partnership-identified sites in 2021 – more than the 97 that Bernacki’s crew tackled through APIPP’s own program, she said.

Collins and Johnson know of areas in the Adirondacks where more attention is needed: A stretch of knotweed runs along Route 28 through North Creek. Bolton Landing has had a serious knotweed problem that the town was addressing, but the Knotweed Management Partnership coordinator there dropped out, Johnson said. Around Otter Lake, outside of Old Forge, knotweed has proliferated, but the group has yet to find a coordinator for that site.

“A volunteer that’s from the community can really make the contacts to help make it more successful,” Collins said. “We’ve made huge, huge, huge progress in Blue Mountain Lake.”

Stem injection can work for small outbreaks but not for acres and acres of plants, Blossey said. He advocates biological control of widely problematic plants by introducing an insect or pathogen that will impede the invader’s rampage.

“Because they’re non-native species, they typically have lost their suite of specialized and other natural enemies,” Blossey said. Biological control involves finding those enemies from the invasive plant’s native territory and, after ensuring they would do no harm to domestic North American species—plants, animals or other bugs—introducing them to infested areas.

Blossey joined an international study on whether a tiny sucking insect called a psyllid, specifically the Aphalara itadori, could successfully take out knotweed. It is safe for native plants, but it isn’t thriving, Blossey said. “It doesn’t seem to be doing much,” he added.

In 2020, he put the psyllid to work in a knotweedy area near Binghamton that he continues to monitor. “It was released and now is in eight or nine different states,” he said. “And basically we can’t find it.”

Blossey holds out hope, though, for another bug that might do better. 

“Eradication is not going to be possible, unless you find the very first plant or the first couple, so that’s out of the equation,” Blossey said. “For me the goal is the reduction in the negative ecological impact so that it becomes just a community member, like everybody else. I don’t want to get rid of it. It can be fine just being here and be pretty when it flowers or whatever, but not dominate everything to the exclusion of all the other organisms.” Bernacki agreed that knotweed is a formidable foe. “Can one site be eradicated? Yes, that’s possible,” she said. “Can an entire township worth be eradicated of knotweed? Probably not, depending on how far it’s gone.”

APIPP has given up on knotweed management in Elizabethtown, for example, one of the worst infestation sites in the park, she said. That thicket would require so much time, labor and funds that it would siphon off resources, Bernacki said.

“We would need hundreds, probably, of landowner permissions to get that under control,” she said. “And that’s just not feasible. Not everyone’s going to let me come on their property and spray herbicide.” 

Not everyone wants to get rid of knotweed. Beekeepers like its fronds of white flowers that bloom in late fall, attracting pollinators that produce knotweed honey. People who forage for wild edibles have harvested knotweed and consumed it as a tea or tincture, even as knotweed pie, for its supposed beneficial properties. The plant contains resveratrol, a compound thought to provide protection against heart disease and some cancers. 

Johnson, though, has dedicated himself to the war against knotweed. His army includes the volunteer coordinators of the Knotweed Management Partnership.

They’ve made progress, he and Collins said. Most of the treated sites in Inlet have had “markedly fewer plants” for as long as four years, he said

In Blue Mountain Lake, Collins said, fewer properties contain the plant and she hasn’t seen it around the lake or along nearby streams for 13 years.

Johnson sees that as proof of the power of a few Adirondack-loving Davids to knock out the Goliath knotweed. “It’s very possible,” he said, “to control it in the Adirondacks.”