Family: Knotweed family (Polygonaceae)
Native Range: Asia
Mile-a-minute is an annual scrambling vine native to Asia that can grow to 25 feet in length. Small, curved barbs cover the stem, petioles, and leaf undersides. These sharply pointed barbs can rip clothing and skin. The plant’s bluish-green leaf is set on long petioles. It is as long as wide (0.75-3.0 inches) and looks like a slightly forked equilateral triangle. Circular bracts are located at nodes along the stem—the stem pierces through these bracts. Small white flowers are located on stalks that extend above these bracts. By June, the flowers have developed into green berries which turn blue later in the summer. Mile-a-minute infests wood edges, open wetlands, and roadsides.
Birds and mammals eat and spread the fruits. Industrial and landscaping equipment picks up and spreads soil contaminated with mile-a-minute seed.
There are native and non-native species that resemble mile-a-minute, but none of these has the combination of barbs, triangular leaves on long petioles, circular bracts, and blue fruits. The University of Connecticut College of Agriculture and Resources (see Sources and Links below) has a visual guide that distinguishes these species.
Mile-a-minute scrambles over and chokes native trees, shrubs, and herbaceous plants. It does best in open, disturbed conditions, where it can dominate acres of wetland and upland habitat.
In the Unites States, Mile-a-minute occurs in Oregon and in eastern states from Massachusetts to Virginia, west to Ohio. In Massachusetts, it was first documented on Cape Cod and in Milton in 2006. Since then, it has been found in several more towns as far west as Greenfield.
Sources and Links:
Pennsylvania Department of Conservation and Natural Resources
USDA Forest Service-Northeastern Area-State & Private Forestry
Invasive.org – IPANE