It grows rapidly. It's nearly impossible to kill. It's terrorized England. And now it's all over my [View all]

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“If it’s growing close to your house, there’s a potential it could send its rhizomes and break through your foundation,” says Jatinder Aulakh, an assistant weed scientist at the Connecticut Agricultural Experiment Station.
Japanese Knotweed Solutions, Ltd.

It grows rapidly. It’s nearly impossible to kill. It’s terrorized England. And now it’s all over my American backyard.

https://slate.com/technology/2019/05/japanese-knotweed-invasive-plants.html

t’s been nearly four years since I bought hypodermic needles at a CVS, squatted in my backyard, and drew them full of glyphosate. I’d done my best to build a little garden in Brooklyn, only to see the ground begin to vanish beneath the fastest-growing plant I had ever seen. It sprouted in April with a pair of tiny, beet-red leaves between the flagstones, and poked up like asparagus through the mulch. By May the leaves were flat and green and bigger than my hands, and the stems as round as a silver dollar. My neighbor’s yard provided a preview of what was coming my way: a grove as thick as a cornfield, 10 feet high, from the windows to the lot line. I had to kill the knotweed.

I was facing twin threats. The knotweed would kill my plants within months and prevent anything else from growing. But spraying the yard with Round-Up, Monsanto’s powerful herbicide, would kill everything in days. Which is why I bought the needles. The idea, which was tested in the journal Conservation Evidence, was to inject the plant’s hollow, jointed canes with weedkiller, shooting herbicide into its roots but sparing innocent neighbors from the deadly spray.

In the moment, this felt absurd, a demented instruction from the Wile E. Coyote guide to gardening. This was before I knew that two full-time knotweed fighters had, in 2004, shot glyphosate into more than 28,000 knotweed stems along Oregon’s Sandy River. Or that in the United Kingdom, it has been a crime to plant or transport unsealed knotweed since 1990. Or that right here in New York City, more than 200 acres of parkland have been overtaken by the plant.

Anyway, it didn’t work.

Japanese knotweed has come a long way since Philipp Franz von Siebold, the doctor-in-residence for the Dutch at Nagasaki, brought it to the Utrecht plant fair in the Netherlands in the 1840s. The gold-medal shrub was prized for its “gracious flowers” and advertised as ornament, medicine, wind shelter, soil retainer, dune stabilizer, cattle feed, and insect pollinator. The stems could be dried to make matchsticks, or cut and cooked like rhubarb. It crested in the dog days of summer with tassels of tiny white buds. Oh, and it grew with “great vigor.”

I tried a few different approaches: Yanking it out stalk by stalk was a sweaty, summer-long game of whack-a-mole—a thankless full-time job. Then a friend and I spent one long night digging a 10-by-4-foot trench, lining it with black contractor bags, and refilling it with dirt. It looked like we were trying to bury something, and in a way we were: the knotweed rhizomes—the plant’s creeping rootstalks—under our feet, searching for a ray of light.

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Knotweed rises on the banks of the Bronx River in New York City, where more than 200 acres of parkland is covered by knotweed.
Henry Grabar