As if the number of invasive plants and insects becoming established in the Upper Delaware River Valley weren’t already ample enough, a new plant is creeping into the local landscape.

The National Park Service (NPS) has announced the discovery of “mile-a-minute vine” (Polygonum perfoliatum), which gets its name from the astonishing growth rate of the annual vine—up to six inches in one day and over 20 feet in one growing season.

The vine is also known as Asiatic tearthumb, due to the prickly stems and leaves that enable it to climb surrounding vegetation and form dense, tangled mats that shade out the sun and choke underlying plants. A similar plant is the commonly found Arrowleaf tearthumb (Polygonum sagittatum), which is a native species and has leaves in the shape of narrow arrowheads.

Mile-a-minute is native to East Asia, and was introduced to Oregon with ship ballast in 1890. In 1946, the species was discovered in Pennsylvania in a shipment of rhododendrons, and today can be found along streams and roadsides, in floodplains and disturbed sites and open woodlands. The NPS discovered the species for the first time in 2011 growing in Lackawaxen, PA in the Delaware riverbank just downstream of the Lackawaxen boat access.

The NPS at Upper Delaware Scenic & Recreational River are tracking the presence of this plant. If you think you have seen the vine growing in the Upper Delaware River valley, call the NPS Resource Management division at 570/729-7842.