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Gary A. Monroe @ USDA-NRCS PLANTS Database

Unless you have been diligent and actively managing your property, you probably have invasive plant species in your yard, a Tree of Heaven, perhaps, or Japanese honeysuckle, or a patch of garlic mustard. In fact, you probably see them in most open spaces as well — the multiflora rose growing along the road, the acres of purple loosestrife at the nearby wetland, the field of leafy spurge at the local preserve. An area twice the size of Delaware is lost to invasive plants each year in the United States.

Invasive plants are typically defined as non-native species that compete vigorously with other species for space and resources, and consequently spread rapidly and take over habitat. Non-natives are also known as “non-indigenous,” “introduced,” “exotic,” or “alien,” and are species that are not naturally occurring in a particular ecosystem. An estimated 5000 introduced plant species now in exist in natural ecosystems in the United States, compared with a total of about 17,000 plant species. It is important to note that not all non-native plants are invasive species. Indeed several non-invasive non-natives are important food crops (corn, wheat, rice) or garden favorites (peonies, roses). Of the non-native wild plants in the country, at least 900 have become invasive.

Invasives are a growing problem. Approximately 42 percent of the plants and animals federally listed as endangered or threatened species are considered at risk primarily because of invasive plant, animal, or microbial species. The increase of non-native plants has recently been linked to the decline of songbirds; robin and thrush nests located in non-native shrubs and trees appear to suffer higher predation rates than those situated in native species. The researchers suggest that characteristics of the native plants in question, such as the presence of thorns or less branch strength, better deter predators.

Invasives cause economic as well as ecological impacts. Invasive species of all types, not just plants, are estimated to cost $137 billion annually in losses to agriculture, forestry, fisheries, and the maintenance of open waterways in the United States. Leafy spurge, which has taken over 5 million acres of the Great Plains, displacing native grasses in prime pastureland, has cost ranchers in the Dakotas, Montana, and Wyoming more than $144 million a year in losses — cattle will not eat it.

Some of the invasives came to the United States unintentionally. Others were brought in for a purpose, such as for ornamental reasons, and then seriously got out of hand. Despite the growing understanding of the detriment to native ecosystems, some invasives are still being propagated and planted, such as purple loosestrife (shown above), which continues to be widely sold in nurseries in several states. More than half of North America's invasive plants arrived here as garden or horticultural introductions.

The federal government has recognized the problem and is working toward finding solutions. In 1999, President Bill Clinton established the National Invasive Species Council “to prevent the introduction of invasive species, provide for their control, and to minimize the economic, ecological, and human health impacts that invasive species cause.” The council has since developed a national invasive species management plan.

As a “backyard habitat manager,” you can do your part, as well.

Remove exotic plant pests! Click here for our action plan and further resources.

Council for Agricultural Science and Technology
Invasive Plant Species – Feb 2000 report outlines increasing economical and ecological threat
http://www.cast-science.org/cast/src/cast_publications.php#30

National Biological Information Infrastructure and the National Invasive Species Council Information and resources regarding invasive species of plants and animals.
http://www.Invasivespecies.gov

Alliance for the Chesapeake Bay
Understanding Invasive Plants – A Background Guide to Identifying Invasive Plants and Using Native Plants in the Home Landscape
http://www.acb-online.org/pubs/projects/deliverables-146-5-2003.pdf

State or Regional Exotic Pest Plant Councils
Mid-Atlantic region: http://www.ma-eppc.org
Pacific Northwest: http://www.wps.org/eppclet.html
Southeast: http://www.se.eppc.org
Michigan: http://forestry.msu.edu/mipc/
California: http://www.caleppc.org