Standing in a patch of Japanese knotweed, Jack Shaida, land protection specialist with Coastal Mountains Land Trust, talks about the invasive plant.

NORTHPORT, Maine — Ever since Bub and Meg Fournier bought their home on about 2 acres in Belfast, they’ve been waging war against a weed.

They can’t let up. They know if they let their guard down, even just a little, the weed will win.

That’s because they’re fighting Japanese knotweed, which is fast-growing, extremely adaptable and characterized by the Maine Department of Agriculture, Conservation and Forestry as “severely invasive.” It’s notoriously difficult to kill, and so hardy it’s been known to grow through asphalt, concrete and even the solid foundations of homes.

But Meg Fournier didn’t really know about any of that before the family moved into their new house about two and a half years ago and found themselves coping with “a jungle” of knotweed that her husband spends much of his free time trying to mow down.

“I’d never really thought twice about knotweed until we bought this piece of property,” she said. “I still forget, until springtime, when you start seeing it pop up.”

The weed that colonized the family’s backyard is, as its name suggests, a native of Asia. It was brought from Japan to the United Kingdom during the Victorian era as an ornamental plant, and even won a gold medal back then at a prestigious flower show, according to the BBC. It came to North America from England in the late 19th century as both an ornamental and to control erosion, but it didn’t take long before its less attractive qualities came to light.

Knotweed, which looks like bamboo but is actually a member of the buckwheat family, is really good at reproducing. It spreads aggressively, sprouting from rhizomes that can be 30 feet long and grow deep underground. It doesn’t take long for it to form a dense, tall thicket that chokes out native plants. It thrives in wet areas, and is especially worrisome along streams and rivers.

“It’s probably one of the worst invasives that we have,” Gary Fish, the state horticulturist, said, adding that it is one of 33 plants that are illegal to sell in Maine. “It takes only a few fragments and you can have a colony. Basically, it’s one that’s very difficult to exhaust by mowing or cutting, unless you’re really tenacious with it. You have to stay on top of it. It stores a lot of energy, and is very apt to keep coming back year after year after year.”

Managing knotweed

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That’s something that Jack Shaida, the stewardship project manager at the Coastal Mountains Land Trust’s McLellan-Poor preserve in Northport, knows very well. The 66-acre preserve features old conifer forests, trails that cross over streams and some frontage on the Little River Reservoir.

Oh, and a field that was largely overtaken by Japanese knotweed.

But Shaida and others at the land trust are working on it. First, they had a tractor operator come in and bush hog the half-acre field. Then, three years ago, they covered the field with huge swaths of geotextile fabric. They expect to leave the fabric on the field for two more.

“The knotweed is losing its strength,” he said. “Every time it sends up a sprout, the root gets weakened.”

But even though it’s been largely starved of sunlight for three years, everywhere there’s a gap in the fabric, it’s possible to see little shoots trying to grow. Knotweed also grows along the edges of the tarp. That’s why the land trust cannot just “set it and forget it:” Shaida and others need to check in on the field periodically to remove the new growth.

“Ideally, you want to come every two weeks, and pick all the sprouts you can,” he said. “You want to go low and get all the roots you can.”

They can’t just leave those roots, or any other part of the plant, in a pile on the ground, or throw them in the back field. That’s a recipe for knotweed disaster, because the plant can easily regrow.

“It can resprout from any of its stems and joints,” Shaida said. “You need to dispose of them either in a trash bag or somewhere they will die.”

A negative picture

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Nancy Olmstad, an invasive plant biologist at the Maine Natural Areas Program, said that other strategies for getting rid of knotweed are the herbicide approach or the grow-and-cut approach.

“I would let it grow a little bit, then cut it. Let it grow a little bit, and cut it,” she said. “You just want to pile the material right there into the patch, or if it’s a small amount, put it in a contractor bag and dispose of it as trash. That would take several years of persistent cutting to exhaust the rhizomes.”

But it’s worth it, she believes — even though some people do like to forage knotweed, whose tender shoots taste a little like rhubarb, and which has some health benefits. Also, beekeepers appreciate that honeybees like its white flowers.

“If you haven’t seen how badly it can change the habitat along our rivers and streams, it might not sink in, the damage it can be doing,” she said. “I certainly think the problems associated with the plant far outweigh any positive aspects of it. When you step back, the picture is pretty solidly negative.”

That’s how midcoast resident Jana McQuilken sees it, too. When she bought her first home in Belfast, she didn’t notice the robust patch of knotweed in its yard. But she caught on quickly.

“I was constantly mowing, mowing, mowing. And every year it kept creeping up the lawn.”

She got a lot of advice from people about how to manage the knotweed. But it seemed to her that they hadn’t succeeded in getting rid of it, either — not with poison, or chemicals, or by covering up the shoots.

It started to get to her.

“I remember having dreams, feeling like it was marching towards the house, getting closer and closer,” she said. “I think it really made me more aware of anything that is not naturally occurring here, and how quickly it can really strangle out more beneficial plants.”