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Purple Loosestrife

Close up of purple loosestrife
Barry Rice



Native to Europe and Asia, and unintentionally introduced to the United States Great Lakes by contaminated cargo ships. It was also introduced by the deliberate importation of seeds. Mature plants can produce up to 2.7 million seeds annually. Seeds are easily spread by water, wind, wildlife, and humans. The seeds can either germinate the following season or lay dormant for several years before sprouting.  

Was first observed in Oklahoma in 1999, in Guthrie Lake.  

Identification Key 

  • Wetland plant with showy purple flower 
  • Flowers arranged on flower spikes (Early July to September) 
  • Leaves are lance-shaped with smooth edges 
  • Square-shaped stem (4 to 6-sided)- multiple woody steams make up a single plant 
  • Grows 3 to 10 feet tall, with 5 feet being the average 


Can grow along shorelines creating dense groups and making it difficult to access open water. Along with outcompeting native aquatic plants and changing the hydrology of wetlands with dense root systems. Purple loosestrife also, provides unsuitable shelter, food, and nesting habitat for native animals.

How To Observe

If you think you have discovered any invasive species contact us at (918) 200-4815 or report online.

Report Online ANS Regulations

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