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Nature Notebook – Purple Loosestrife

Spots of purple dot the edges of rivers, lakes, and ditches around southwest Michigan in the late summer. Many people enjoy the bright color of the purple loosestrife plant as they boat and hike around, but this plant is invasive and has been causing problems for native plants and animals since its arrival in 1850.

Lythrum salicaria grows to about three to seven feet tall and has around fifty short stems with purple flower spikes on them. Purple loosestrife spreads rapidly through seeds and roots, pushing out native plants. This is also a problem for wildlife, which rely on native food sources and can’t eat the nonnative loosestrife.

Itis native to Eurasia, where the plant has natural beetle predators that keep the plant in check. In the United States and Canada, this beetle was not formerly present but has since been released as a biological control agent on the plant throughout the country. Research has been done to ensure these two small beetles will only eat purple loosestrife and hopefully control the population.

Homeowners can help by not purchasing lythrum salicaria from nurseries and by planting native plants in their yards.