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.

Status in the CKISS region

  • Purple loosestrife is classified as Eradicate/Annual Control on the CKISS Annual Priority List.
  • There are numerous purple loosestrife sites in the Nelson and Slocan Invasive Plant Management Areas (IPMAs), so it is considered a Contain species in those areas, and the goal is to prevent it from spreading further.
  • Several IPMAs in the CKISS region have very little purple loosestrife or none at all, so for these areas it is considered a Regional EDRR species
  • To learn more about how CKISS classifies and manages invasive species, see our Invasive Species Priority Lists page.

Integrated pest 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.
  • Become PlantWise and use Grow Me Instead to choose non-invasive lookalikes for your garden.

Additional resources