Live in Massachusetts? This invasive plant could damage your house’s foundation.

Japanese knotweed, an invasive plant that's extremely difficult to get rid of, has moved into wetlands and pine barrens across Massachusetts.

When construction began in their Saugus neighborhood more than a decade ago, couple Bob and Rosanne Maher slowly began noticing a weed growing on their property. Now, they’re seeking help from the town.

But Japanese knotweed isn’t just a weed. It’s a rapidly growing invasive plant that, when left unchecked, grows fast, tall, deep, and big. Bob said they’ve used chemicals to kill it, placed tarps to starve it out, and have tried to pull it up from its root.

“The stuff is hard to get rid of,” Bob told Boston.com.

KNOTWEED:

The Mahers went to Saugus’s Planning Board last month to urge the town to help contain the plant. Right now, the weed is encroaching on their Fiske Avenue home where they’ve lived for more than two decades.

The relentless weed has already breached their neighbor’s property and is threatening nearby wetlands. Rosanne told Planning Board members they’ve spent hundreds of dollars to get the knotweed under control.

“If we were ever to sell our home, that’s something that we would have to address,” she said. “They wouldn’t necessarily want to buy the house because it’s very difficult to get rid of.”

Japanese knotweed has large heart-shaped leaves and hollow bamboo-like stems. It grows in dense clumps and sprouts cream-colored flowers in August.

The knotweed’s rhizomes bury up to 10 feet deep, and its lateral coverage can be up to 40 feet underground. It takes years of work to remove it completely, and the plant should be disposed of properly to prevent further spread.

Last year, a family won $300,000 from a developer who they claimed spread the weed in their yard.

‘It can grow through pavement’

The weed is widespread in the Nashua River Watershed near Groton, a scientist with the watershed said. Groton has its own Invasive Species Committee with volunteers working to educate and eradicate plants locally. Jonathan Basch, co-chair of the committee, said they’ve been successful in reducing Japanese Knotweed, while using less herbicides.

Basch said injecting the stem directly with herbicide at the right time of year is effective in killing the plant.

“It can become a really big problem over time, and because it grows so densely, it can grow into foundations,” Basch said. “It can grow through pavement.”

Indigenous group looks to restore land from knotweed

A Indigenous-led conservation group wants the knotweed gone off the Wampanoag Common Lands — a 32.4 acre donation and former summer camp in Kingston. The Native Land Conservancy is working to restore the land to how the Wampanoag would have experienced it hundreds of years ago.

“With the Wampanoag having had a millennia of relationship with this land, we’re in it for the long run,” NLC Executive Director Diana Ruiz said. “We’re not going to rush it for the sake of getting it done sooner.”

Ruiz said they are battling two stubborn patches of knotweed on the Wampanoag Common Lands. She said the former summer camp’s buildings were removed when it was donated to the project.

“With that disturbance, there’s all these open ecological niches that are there and that kind of makes it ripe for invasive plants to take over,” she said.

Ruiz said they cut one patch down and covered it with a thick, heavy tarp to prevent photosynthesis. The plant stores energy in the ground and can even break through to sunlight.

“It’s not the most beautiful strategy, but it is a way of not using chemicals, preventing the spread, and as an added bonus, the garter snakes seem to enjoy living underneath the tarp,” Ruiz said.

Another patch of Japanese knotweed is along Muddy Pond — a healthy patch, Ruiz said, which will take longer to weaken.

“We’re slowly depleting those underground resources, digging up the rhizomes, starting from the outer edges of the patch, while introducing soil stabilizing plants and plants that could shade and outcompete the knotweed patch or at least keep it in check as we slowly work it back,” she said.

The Mahers said Saugus officials are doing their best to address the rapidly spreading weed, which they say was brought in the dirt fill brought by construction workers.

“You want to take care of your house. You want to spend time with your family and everything else,” Bob said. “Every time you go out to mow your lawn, you go, ‘this is back again.’”