Purple Loosestrife

purple loosestrife has taken over this wetland

Purple loosestrife (Lythrum salicaria) is a showy, purple flowering shrub native to Eurasia. It can be found in wetlands, marshes, wet meadows, river banks, lake shores, ditches and other wet areas. Though purple loosestrife was first reported in North America in 1814, its abundance in Multnomah County is still minimal and we wish to keep this weed from becoming widely established throughout the county.

Because of its high rate of seed production this species can dramatically increase its population size when conditions are optimal. The seeds are easily dispersed by wind, water, wildlife, livestock, and people. It can also spread vegetatively by re-sprouting from cut stems and regenerating from small pieces of dislodged root stock. Purple loosestrife is detrimental to native wetland vegetation and wildlife, particularly water fowl, because it displaces native plants used for forage. If left unchecked purple loosestrife will continue to spread outward, creating immense stands consisting only of itself.


Purple Loosestrife is a stout, multi-stemmed perennial forb with a strongly developed taproot. It ranges between 3 and 10 feet in height. Its woody stems have four to six angular sides. This plant dies back each year. It has downy leaves that are lance-shaped and rounded or heart-shaped at the base and are whorled or oppositely arranged. The most easily identifiable feature of purple loosestrife is its extremely showy flower. Purple loosestrife plants produce many flower spikes that top the shrubs with primarily magenta colored flowers from July through September or October. White or light pink flowers are occasionally produced. A mature plant can grow 30-50 stems.

Report Sightings!

If you think you have found this plant please report it immediately. This plant is on our EDRR list, and we provide free control east of the Sandy River. Unfortunately, due to the abundance of this species in other areas, we cannot offer free control everywhere. Report a sighting!

More Photos

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