Purple Loosestrife


Purple loosestrife is a wetland plant, growing in freshwater wet meadows, marshes, river and stream banks, pond edges, reservoirs, and ditches. It prefers moist soils but can tolerate a wide range of conditions. It can withstand shallow flooding, and tolerates up to 50% shade. It flowers from July until September or October. A mature plant produces about 2,700,000 seeds a year.

How It Spreads

Purple loosestrife was likely brought to North America in the 1800s both intentionally, as an ornamental plant, and unintentionally, by ships dumping ballast or European raw sheep wool that contained seeds. Humans have continued to transport it throughout the U.S. as a landscaping plant and as a food source for bees due to its nectar-producing capabilities. Purple loosestrife spreads naturally through either vegetative spread or through seed dispersal. Additionally, animals and humans can be a vector of transport when seeds stuck in mud are attached to bodies, equipment, or vehicles.

Impacts to Rivers

Purple loosestrife can form monotypic stands that outcompete native wetland plants and can change the soil and water chemistry of the ecosystem. It can have a negative impact on tadpoles and birds, such as black terns, least bitterns, pied-billed grebes and marsh wren. Additionally, other marsh birds that prefer to nest in native marsh grasses are negatively impacted by purple loosestrife stands since the native grasses, sedges and flowering plants supply a higher quality of cover, food, or nesting sites.


River Alliance of Wisconsin Factsheet (Lower Wisconsin River Basin AIS Strategic Plan)

Wisconsin Department of Natural Resources Factsheet

Purple Loosestrife Brochure Including Common Look-A-Likes