Purple Loosestrife (Lythrum salicaria)

Purple loosestrife (Lythrum salicaria) is an invasive perennial plant that is spreading rapidly in North American wetlands, shorelines, and roadside ditches. Thick stands of purple loosestrife crowd out native plants and reduce food, shelter, and nesting sites for wildlife, birds, turtles, and frogs. After multiple introductions in the 1800s for bee keeping, as an ornamental plant, and in discarded soil used as ballast on ships, this European species has invaded nearly every U.S. state and at least six Canadian provinces.

Gardeners, waterfowl hunters, and other outdoor enthusiasts should know how to identify purple loosestrife - detecting new infestations can prevent the spread of this plant. Report new sightings and help control purple loosestrife.

Identify Purple Loosestrife

General Characteristics

  1. Mature plants have many stems that grow from a…
  2. Root crown
  3. Dead stems stand until spring
  4. Height 3 to 7 feet (1 to 2 meters)
  5. Spike covered with many flowers
  6. Downy, smooth-edged leaves
  7. Leaves usually paired, opposite
  8. Stem has ridges
  9. Flower has several pink-purple petals

What You Can Do

  • Learn to identify purple loosestrife.
  • Do not transplant it!
  • Avoid planting seed mixures containing purple loosestrife.
  • Inspect and remove aquatic plants, seeds, and mud from equipment, clothing, and footwear.
  • Contact a state agency below to get involved with control efforts in your area.
  • Report small new sightings (less than 100 plants) - note exact location; wrap a segment of plant stem, leaves, and flower spike (if in season) in a wet paper towel, place in a sealed plastic bag; and call Minnesota Sea Grant Program in Duluth, (218) 726-8712, or the Minnesota Department of Natural Resources in St. Paul, 1-888-MINNDNR or (651) 259-5100, or a local DNR fishery office.

Know the rules!

Specimens are needed to confirm sightings, but some jurisdictions prohibit or discourage possession and transport of purple loosestrife and other invasive aquatic plants and animals. Contact your local natural resource management agency for instructions. Unauthorized introduction of plants or fish into the wild is illegal. Protect your property and our waters.

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This page last modified on July 26, 2013     © 1996 – 2014 Regents of the University of Minnesota     The University of Minnesota is an equal opportunity educator and employer.
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