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Floating Primrose-Willow

Ludwigia peploides
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What is Ontario Doing?

To prevent this unwanted invader from coming into the province, Ontario has regulated floating primrose-willow as restricted under the Invasive Species Act, 2015.  


Floating primrose-willow is an herbaceous perennial aquatic plant native to South America, Central America, and the southeastern United States. It is a popular ornamental and water garden plant that can outcompete native plants and take over aquatic ecosystems when released into the wild or spread to a new areas. 


Floating primrose-willow can easily form free-floating mats that can, when broken off, spread to new areas. It has been found all along the east coast of the US, as well as in states along the Great Lakes, and in western coastal states. In Canada, positive reports of this plant have been made in the Cedar Creek-Frontal Lake Erie area.

Impacts of Floating Primrose-Willow

  • Can easily be transmitted from waterbody to waterbody and grows aggressively to compete with native plants. 
  • Forms dense mats of floating vegetation, blocking available sunlight to submerged plants, reducing water quality, and removing fish habitats. 
  • Mats can dislodge and cause stagnant waters as they decompose, killing native plants and animals. 
  • Dense mats can hinder recreational activities, such as boating, angling, and swimming. 

How to Identify

  • Leaves are smooth, green, and arranged in an alternate pattern. Leaves can be in one of two shapes: early growth leaves are rounder, while mature leaves are oval. 
  • Flowers are a strong yellow colour with five petals. 
  • Stems are reddish to brown and can be up to 3 metres (9 ft 10.11 in) long. 
  • Roots form at the nodes of the stem and can reach downward into the substrate. 

What You Can Do

  • Learn how to identify floating primrose-willow and how to prevent the introduction or spread of this plant with your watercraft and/or fishing equipment. 
  • Never buy, plant, or keep floating primrose-willow in your aquarium or water garden. It is against the law to buy, sell, trade, possess, or transport floating primrose-willow. 
  • Never deposit unwanted aquarium or water garden plants into Ontario’s lakes or rivers. Dispose of them in the garbage or at least 30 metres (32 yards) away from any waterbody. 
  • Clean, Drain, Dry your boat, trailer, and equipment after each use, be sure to remove all plants, animals, and mud before moving to a new waterbody. 
  • If you have any information about the illegal importation, distribution, or sale of floating primrose-willow , report it immediately to the MNRF at 1-877-847-7667, toll-free anytime. You can also call Crime Stoppers anonymously at 1-800-222-TIPS (8477). 
  • If you’ve seen a floating primrose-willow or another invasive species in the wild, please contact the toll-free Invading Species Hotline at 1-800-563-7711, visit EDDMapS, or search for the ‘Invasive Species in Ontario’ project on to report a sighting. 


OFAH/OMNRF Invading Species Awareness Program. (2023). Floating Primrose-Willow. Retrieved from:
This factsheet may be reproduced for non-commercial purposes.

Header photo bybobvirag | iNaturalist 

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