ANNAPOLIS, MD (October 21, 2004)
(photo: Britt Slattery, U.S. Fish and Wildlife Service, www. invasive.org)
The name alone says it all - this is one fast growing plant! Mile-a-minute weed (MAM),
also known as devil’s tail tearthumb, is an herbaceous, annual, trailing vine in the
buckwheat family (Polygonaceae). It is native to Asia and was introduced into the e
astern U.S. (York County, Pennsylvania) during the 1930s for ornamental interest.
MAM is reported to be a problem in Wisconsin and in nine states in the northeast and
mid-Atlantic including Connecticut, Delaware, Maryland, Massachusetts, New Jersey,
Pennsylvania, Virginia, West Virginia, and Washington, D.C. It has the potential
to spread and establish throughout much of the U.S. These credentials have earned
MAM the prestigious spot as “Invader of the Month” by the Maryland Invasive Species
Council for October 2004.
Known scientifically as Polygonum perfoliatum, MAM is a sun-loving plant that
prefers moderate to full sunlight and moist conditions. It invades forest edges,
stream banks, wetlands, roadsides, uncultivated fields, fence lines and other
disturbed, open sites. It grows very rapidly, scrambling over low vegetation
and up tree branches into the canopy. Thick blankets of MAM vines smother and
kill native plants by blocking light and preventing photosynthesis.
The stems and leaves of MAM are armed with downward pointing hooks or barbs
which help it hold onto vegetation as it climbs. These barbs also make it
difficult to walk through infested areas and painful to remove MAM by hand. The
leaves are distinctly shaped like an equilateral (equal-sided) triangle and
alternate along the narrow, delicate stems. Like most polygonums, a small
collar-like structure surrounds the stem at each node. Flowering begins in
June or July and continues through the growing season. The small, light
green, inconspicuous flowers are followed by clusters of colorful blue-purple
fruits each containing a single glossy, black or reddish-black seed.
Birds are attracted to the colorful fruits of MAM and are apparently its
primary long-distance dispersers. MAM seeds are transported locally by ants
that are attracted to a small food body on the seeds. The ants feed only on
the food body and may help the survival of MAM by inadvertently planting the
seeds. Water may also play an important role in dispersal. Its fruits can
remain buoyant for 7 to 9 days and may be carried during flood events.
Weevil to the rescue? A biological control agent has been investigated for
control of MAM and is planned for a test release into the wild in Delaware.
This knight-in-shining armor is a tiny orange weevil with the scientific name
Rhinoncomimus latipes that is specific to MAM in China. Adult weevils feed
on foliage and the larvae tunnel through the stems, causing defoliation,
wilting and death of MAM under heavy feeding pressure.
Small infestations of MAM can be removed by hand while wearing leather gloves,
long pants, and a long-sleeved shirt to prevent scratches and cuts from the
barbs. Removal of vines before fruits are produced will help prevent buildup
and spread of seed. If fruits are present, the vines should be balled up,
bagged, and disposed of in a landfill. For practical purposes, large
infestations require treatment with herbicide. Controlled areas need to
monitored throughout the summer and retreated as necessary. Due to the
continual spread of seed, and seed remaining in the soil, favorable sites
may unfortunately remain infested for years to come.
For more information about other Invasive
Species of Concern, visit www.mdinvasivesp.org or call MDA at 410.841.5920.
photos available electronically on request.