ANS Task Force
Purple Loosestrife
( Lythrum salicaria )

Purple LoosestrifeDESCRIPTION: Plants are erect, emmersed, much-branched perennials, glabrous to often pubescent, growing to 1 m tall. The stems are 4-angled. The leaves are opposite or whorled, sessile, mostly longer than the internode above, 2-10 cm long, 0.5-1.5 cm wide, the base obtuse to cordate. The flowers are whorled in showy terminal bracteate spike-like inflorescences. The 6 petals are rose-purple, to 10 mm long. There are usually 12 stamens. Plants grow in marshes, lakes, along river margins, wet meadows, prairies, and ditches. It is estimated that one plant may produce 2.5 million seeds.

PATHWAYS/HISTORY: This species is naturalized from Europe, first reported in the U.S. along the northeast coast in the early 1800's. Due to its attractive flowers, it has been planted as an ornamental garden species and has escaped from cultivation; it is now in at least 40 states and Canada.

RISKS/IMPACTS: Often populations have spread so aggressively that native vegetation is excluded. Several garden races, some with larger rose-red petals, have been produced from this species and are cultivated. It is estimated that 200,000 ha of wetlands in the U.S. are lost annually through invasions of this species.

MANAGEMENT: Hand pulling is an effective and selective way to remove purple loosestrife. It is best done while plant is in flower before it goes to seed (July or August). Cutting may be used to contain large populations of loosestrife by reducing stem numbers and seed production. A loosestrife-eating beetle (Galerucella) is sometimes used as a biological control. Herbicides must be used with extreme caution because herbicides are non-selective and will hurt the nearby vegetation.

WHAT YOU CAN DO: Although you may find purple loosestrife available for sale, do not purchase or intentionally plant this species. If you have purple loosestrife growing in your yard, pull it out and replace it with native vegetation.

PROFILE CREDIT: David Webb - IMAGE CREDIT: Martha L. Walter, Michigan Sea Grant


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