In June, I swapped my trowel and pruner for a backpack and boots and set off for a couple of weeks on the Appalachian Trail in Pennsylvania. I’ve been hiking the AT for several years now, and along with the beautiful vistas, good company, and random surprises there have been some unsettlling experiences: crackling thunderstorms, snakes, bears, and a few weirdos. All of that I took pretty much in stride. Then I encountered mile-a-minute weed.

I was making my way southward along the ridge toward Swatara Gap. The rain had stopped, and I was enjoying the airy wildflowers and black raspberries as I rock-hopped and tiptoed around the poison ivy. Then I saw it: a basketball-court-sized patch of solid green blanketing the ground and anything upright in its path.

Much of the Appalachian Trail in Pennsylvania is a woodland ridge walk, with occasional views of the farmland to the south.		A short walk away from the scene in the photo at left, a sea of alien green has engulfed the landscape.
Mile-a-minute weed is easily identified by its leaf shape and chartreuse color. The leaves, oddly, are equilateral triangles. The vine looks like something out of a horror movie (it can grow up to 6 inches a day under ideal conditions), and in my imagination it seemed to be advancing toward me. Usually when I stop, I have some water or a snack, but this time I thought it best to move on quickly before I was swallowed up. Silenty, I gave thanks that my home garden has been spared this scourge.

Safe for now, but maybe not for long
Mile-a-minute vine (Persicaria perfoliata, formerly known as Polygonum perfoliatum), a Chinese plant introduced accidentally to the United States as a contaminant of ornamental stock. It first became established in Pennsylvania in the 1930s and has been spreading ever since. It has been reported as invasive in Virginia, West Virginia, Delaware, Maryland, District of Columbia, New Jersey, New York, Massachusetts, and (alas) Connecticut.

Probably it’s just a matter of time until those scary chartreuse triangles show up in my wineberry patch. But when they do, I’ll attack vigorously. Mile-a-minute weed is an annual, not a perennial, so the trick is to get it before it sets seed, which will winter over and produce new vines the following year. Small patches can be controlled by hand-pulling or even mowing. Biocontrol experiments are underway in Maryland and Connecticut to eradicate the plant with the mile-a-minute weevil (Rhinoncomimus latipes Korotyaev).

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