It’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 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…..