Purple loosestrife invades riparian areas, displacing native vegetation and reducing biodiversity

Purple loosestrife

(Lythrum salicaria)


  • Introduced from Europe and Asia to the Atlantic coast of North America in the early 1800’s.
  • Up to 2 meters tall with several stalks covered in pinkish-purple spike-like flowers.
  • Flowers bloom from late June through to September.
  • Square 4-sided stem, lance shaped leaves that are arranged opposite from each other.
  • Grows in wet/riparian areas.

Consequences of invasion

  • Forms dense stands with thick mats of roots, which degrades wetland habitats.
  • Decreases biodiversity.
  • Large infestations can clog irrigation canals, degrade farm lands and reduce forage values of adjacent pastures.

Management Options

  • The best time to remove Purple Loosestrife is June, July and early August, when flowers can be seen but before seeds have formed.
  • Dispose of Purple Loosestrife by bagging and disposing at your local landfill. See our In the Garden page to learn more about proper disposal.
  • Biocontrol agents are available in BC for this plant.

Additional resources:

Purple Loosestrife | ISCBC
CKISS Downloadable Profile
Purple Loosestrife Best Management Practices | ISCMV
Purple Loosestrife | Ontario’s Invading Species Awareness Program
Manitoba Purple Loosestrife Project
Invasive Plants with Biocontrol | BC Ministry of Environment