Mile-a-Minute Weed

November 10, 2020

Mile-a-Minute Weed

Photographer: Dale Chadwick
Summary Author: Dale Chadwick

The mile-a-minute weed (Persicaria perfoliata) is an invasive plant introduced into the United States from Asia. The current infestation started in a nursery in York County, Pennsylvania. A nurseryman found it in some imports in the 1930s and liked its appearance. It was several decades, however, before it escaped and became a problem. I first noticed it when I moved to Lancaster, Pennsylvania in 2000. It has distinctive triangular leaves and upon inspection, I immediately realized where it got an alternate name, Asian tearthumb. Note the thorns in the center image.

It grows in open areas along roads and streams, is fast-growing and can overwhelm other plants. In the image on the right, it's growing on and pulling down a wild lettuce plant. In the background, it can be seen overgrowing ferns in the sunny part of the area along the Enola Low Grade Trail in southern Lancaster County.

Mile-a-minute weed produces small, edible blue berries and is spread by birds, mammals and insects. It's an annual and is killed by even a mild frost, but the seeds retain viability for up to 6 years. Once established the plant is hard to eradicate. There's been some success controlling the plant with the mile-a-minute weevil (Rhinoncomimus latipes). Images taken August 5, 2020.