What to do about Japanese knotweed?

The end of my yard is anually infiltrated by Japanese knotweed, encroaching from the overrun lot behind it, and anually beaten back with machete and glyphosphate (dutifully applied into the root). I know that it's futile, and so does anyone else confronted with the invasive menace.

England and Wales are the most dramatic examples of knotweed's spread in the West, but knotweed endures across the channel, too—as the most expensive invasive plant crisis on the continent, according to a 2009 study. And in recent decades, Japanese knotweed has colonized the Northeastern United States, the spine of the Appalachians, the Great Lakes states, and the Pacific Northwest. Infestation is "rapid and devastating," one researcher wrote. "The plants are characterized by a strong will to live," wrote another. In New Hampshire, a knotweed researcher told me he had found knotweed systems—almost certainly just one plant, connected underground—as large as 32,000 square feet, more than half the size of a football field.

Photo: Angus MacAskill