Invasive Plant Profile: Mile-a-minute (Polygonum perfoliatum)

You’ve probably seen a new plant in our neighborhood, growing along the roadsides, and overtaking brush piles and meadows. It has light blue-green triangular leaves, and sapphire-blue fruit. There are small barbs on the stem, lending its other common name: devil’s tear-thumb. As the common names imply, it both grows quickly and is a pain to try to control. And as its scientific name suggests, mile-a-minute can be distinguished from native tear-thumbs (which typically grow in wet areas) in that the stem runs through (per) the leaves (foliatum).

Mile-a-minute is an annual, so it grows up to 15 feet from seed each year. It can quickly overwhelm small trees and shrubs and displace native vegetation. Introduced by accident to this country in a nursery container, it has spread throughout the Mid-Atlantic states in the last few years.

Five years ago it was found only in a patch of wild raspberries along Pine Creek in nearby State Game Lands. Over the last few years we have been hand pulling it from places where it has showed up in Crow’s Nest: sandbars along Pine Creek where natural stream flooding prepares a seed bed, and the gap in the forest canopy created by the creek provides the sun it needs.

Although we have successfully removed an overwhelming majority of these plants before they set seed, we have not made much progress because there is an upstream seed source, birds eat and spread the seed from elsewhere, and seeds may remain viable in the soil for several years.

In 2002 we found mile-a-minute in three other locations at the preserve, where we also aggressively have tried to control it. At that time the mile-a-minute had taken over several acres of Chinese bush clover planted for game habitat on nearby SGL #43. In 2003 we found mile-a-minute in isolated populations throughout the preserve, and have continued to remove it.

Mile-a-minute is a Pennsylvania noxious weed; it is listed by the Department of Agriculture to limit its spread and growth. It is illegal to sell or transport it, and landowners who have it can be required to get rid of it.