There are a lot of invasive weeds in Massachusetts. Knotweed is the worst. It is spreading along waterways and is often seen along the community trails. It is all over the Alewife Reservation and other preserved areas.

Knotweed is one of many plants that spread underground and pop up along cracks in sidewalks and asphalt. Knotweed is the strongest of these; it destroys building in its way. In a post from Slate.com, the reports from England include stories of knotweed working its way into basements and through the floorboards of the building.

In 2000, biologists Michelle Hollingsworth and John Bailey analyzed 150 samples from across the U.K. and concluded that British knotweed was all a clone of that original plant, now one of the world’s largest. The DNA was identical. Not just one species but a single plant had conquered the entire United Kingdom. [Slate.com]

It’s one plant. It doesn’t have any diseases. It spreads underground. It grows so densely that nothing else can use the land with it. It grows in walls and through basements and floorboards.

Knotweed and real estate

For these reasons, Knotweed is the one that has real estate implications. It’s been in England since 1850 and it is now a real estate issue there. America got its first piece of knotweed in 1860. Some ended up in the New York Botanical Garden.

Fast forward 160 years and English banks are not giving mortgages to properties that have knotweed. In America, neighbors are suing when one person’s uncontrolled knotweed that spreads to their neighbor’s property.

At the heart of the Great British Knotweed Panic is the fear that knotweed will make your house fall down. The U.K. has made knotweed disclosure mandatory on all deeds of sale. British banks will not issue a mortgage to a property with knotweed on its grounds, or to one with knotweed growing nearby, unless a management plan is in place. [Slate]

The first American lawsuit about knotweed was in New York:

The first American knotweed lawsuit, as far as I can tell, was decided in 2014, when Cynthia and Alan Inman of Scarsdale, New York, sued the owners of the shopping center next door, alleging the defendants had allowed knotweed to thrive on their property and, from there, undermine the Inmans’ property value. They won $535,000 in damages. [Slate]

What to do about knotweed?

Japanese knotweed in yardI found my very first sprig of Japanese Knotweed in my yard this spring. I promptly declared war. My gardening friends came forward with support and advice. The crux of the advice I got was this:

Dig it up. Dig it up soon. Dig it up entirely.

Dig it up. Then starve it:

  1. Cover the ground with black plastic. Let everything die. Then start over with all the plants there.
  2. For big shoots, pull off the leaves and cut it back. Then put wire around the stalk to strangle them when they start to regrow.

A few days later, a friend posted this Slate blog on Japanese Knotweed. That didn’t cheer me up. It’s the information above about how the stuff eats houses.