UW-Extension Cooperative Extension
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Contact: Robert Korth
Email: (715) 346-2192
Entry Date: June, 2001
File Under: Natural Resources
People Can Help Control Spread Of Purple Loosestrife
Your Town - (YOUR TOWN) - Masses of pretty purple flowers waving in the breeze along highways, near marshes, wetlands and in lakes are actually an exotic plant species that can endanger native plants.
"Purple loosestrife is sometimes mistaken for Blazing Star, Fireweed or blue Vervain, but the non-native plant can overtake a wetland, literally shading out the native vegetation, including rare or endangered plants," explains Robert Korth, University of Wisconsin-Stevens Point/Extension lake management specialist.
"Loosestrife threatens native plant communities and also the wildlife that depend on the native vegetation for food or shelter," Korth adds.
As loosestrife dominates a wetland, traditional residents, such as muskrat and waterfowl decline in numbers. Marsh wrens and least bitterns are displaced completely from the wetland.
"Loosestrife itself doesn't provide much in the way of food or habitat for wildlife species," Korth says. "Its woody stems are unpalatable to many species."
Loosestrife was introduced in the United States as a garden plant. Since 1987, Wisconsin state law bans the sale, distribution, planting or cultivation of non-native purple loosestrife.
Honeybees are the main pollinator of purple loosestrife, and they commonly travel up to two miles during heir forays.
"Purple loosestrife spreads primarily by seed, but also can spread from broken-off stems that root themselves in moist soil," explains Korth. "Loosestrife plants produce more than 100,000 seeds per year."
Although most fall in the area of the parent plant, water, birds, animals and people can transport seeds long distances.
Loosestrife is easiest to identify when it blooms, from early July into early September. It grows above the water surface, two to seven feel tall, and the stems die back each year. Flowers grow in long spikes.
"Prevention is the best way to stop the purple loosestrife invasion," Korth says.
-- Be on the lookout for pioneering plants or isolated small colonies, especially in areas otherwise free of loosestrife. Remove pioneer plants immediately.
-- Rinse off equipment, gear, clothing and footwear used in infested areas before moving into uninfested areas.
-- Remove and destroy purple loosestrife planted in lawns and gardens.
-- Do not move or transplant purple loosestrife.
-- Small, young plants can be hand-pulled, but make sure o remove the entire root or they will resprout. It's best to remove the plant before the onslaught of seeds, early August.
-- Careful use of herbicide is the most effective, efficient and least destructive way to remove large purple loosestrife plants. A permit is required from the Department of Natural Resources when applying herbicides to Wisconsin waters.