Wisconsin Department of Natural Resources

Purple Loosestrife

Source: Wisconsin DNR Aquatic Invasive Species program

Date: 2009 to present.* Metadata last updated 11/11

Note: * The purple loosestrife locations shown in the Surface Water Data Viewer are incomplete. Only locations reported and confirmed in conjunction with the Wisconsin DNR since 2011 are reflected. For additional purple loosestrife occurrences, please visit the Great Lakes Indian Fish & Wildlife Commission's web mapping tool (maps.glifwc.org [exit DNR]).

This data represents wetlands where infestations of purple loosestrife are known to exist. These invasive perennial herb may be growing in other wetlands, but their presence has not been confirmed outside of the wetlands listed here. Purple loosestrife monitoring is conducted on Wisconsin's wetlands in the summer months, with the infestation data compiled in the fall.

Purple loosestrife is a perennial herb 3-7 feet tall with a dense bushy growth of 1-50 stems. The stems, which range from green to purple, die back each year. Showy flowers vary from purple to magenta, possess 5-6 petals aggregated into numerous long spikes, and bloom from July to September. Leaves are opposite, nearly linear, and attached to four-sided stems without stalks. It has a large, woody taproot with fibrous rhizomes that form a dense mat. By state law, purple loosestrife is a nuisance species in Wisconsin. It is illegal to sell, distribute, or cultivate the plants or seeds, including any of its cultivars in Wisconsin.

For more information, please visit the Invasive Species pages.