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Wetland Plants and Plant Communities of Minnesota and Wisconsin


(Lythrum salicaria L.)

Purple Loosestrife



FIELD CHARACTERISTICS: A stout, perennial herb with woody-like square stems growing to a height of 0.6-2.0 m. Plants may be smooth or hairy. Leaves are 3-10 cm. long, lanceolate, opposite or whorled in 3's, entire, sessile, and sometimes clasping the stem. Spikes are elongate (1-4 dm.) and packed with red-purple flowers composed of 6 petals. In flower from June to September.

ECOLOGICAL NOTES: Purple loosestrife is a persistent emergent found in deep and shallow marshes, inland fresh meadows, and shores of lakes and streams. It is often associated with wetlands that have been disturbed by agricultural use, drainage, pasturing, siltation, or water level fluctuations.

Introduced from Eurasia, this aggressive invader poses a serious threat to North American wetlands because it can outcompete native wetland plants and take over wetland habitats. Although colorful, purple loosestrife, has no appreciable wildlife food or cover value, whereas the native species it replaces are valuable for wildlife. The extensive monotypes that can be formed by purple loosestrife result in a loss of plant and animal diversity.

SOURCE: Fernald (1970); and Gleason and Cronquist (1991).

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