Purple loosestrife

Purple loosestrife (Lythrum salicaria )isan aggressive wetland plant species first introduced into the United States from Europe. It is a showy, attractive plant that grows up to 4 feet (1.2 m) in height with pink and purple flowers arranged on a spike, and it is common in shallow marshes and lakeshores all across the northern half of the United States.

Loosestrife is a perennial plant species that spreads rapidly because of the high quantity of seeds it produces (sometimes up to 300,000 seeds per plant) and the efficient dispersal of seeds by wind and water. The plant has a well-developed root system and is able to tolerate a variety of soil moisture conditions. This has made it an effective colonizer of disturbed ground as well as areas with fluctuating hydrological regimes. Because of its attractive flowers, it has also been planted as an ornamental species.

As a highly adaptive and tolerant plant, loosestrife is often able to outcompete native plant species in many environments, particularly in wetlands and disturbed areas. Other species often have difficulty surviving once it becomes established, and loosestrife has low value as food and nesting habitat . For example, the cattail plants in many wetlands of New York state have been replaced by purple loosestrife. Wildlife experts prize cattails as plants whose roots and tubes are of high value as food source to small mammals and rodents, and the spread of loosestrife has led to a decline in the habitat values of these wetlands. So, in spite of its pleasing appearance, New York and a number of other states have embarked on purple loosestrife eradication programs.

The most commonly used chemical method for eradicating purple loosestrife is a herbicide known as Rodeo--a selective herbicide that kills only dicotyledonous or broadleaf plants. When a diluted solution of Rodeo is sprayed directly on mature leaves, it disrupts protein synthesis and causes plant death within two to seven days. Physical removal of the plants by mowing early in the growing season, prior to seed set, has also been effective in keeping areas free of loosestrife.

See also Introduced species

[Usha Vedagiri ]

RESOURCES

BOOKS

Schmidt, J. C. How to Identify and Control Water Weeds and Algae. Milwaukee, WI: Applied Biochemists, 1987.

Thompson, D. Q. Spread, Impact and Control of Purple Loosestrife (Lythrum salicaria) in North American Wetlands. Washington, DC: U.S. Department of the Interior, 1987.

——. Waterfowl Management Handbook. 13.4.11, Control of Purple Loosestrife. Washington, DC: U. S. Fish and Wildlife Service, 1989.