When aquatic and wetland plants become invasive, they can threaten Ontario’s waterways in a multitude of ways. Aquatic and wetland invasive plants are non-native species introduced to Ontario from outside their normal range by human activities and threaten the environment, economy, or society. These species can often grow fast and form dense mats, which alter light and nutrient availability, out-compete native plants, lower biodiversity and threaten species at risk. Dense mats create stagnant waters, which can support mosquito populations and contribute to algal blooms. During die-back, dense mats reduce dissolved oxygen, which can be lethal to fish and other aquatic organisms. Aquatic and wetland invasive plants can also inhibit recreational uses of waterways (such as boating, swimming or angling), disrupt storm drainage or hydro-electrical generation, increase flood probability, and impact water quality.
In recognition of the damage these aquatic and wetland invasive plants can cause, in 2013, Ontario developed an Aquatic Invasive Plant List of priority species of concern to enable work to safely remove them from provincial crown land and shorelands. The Aquatic Plant BMP document provides information on thoseoriginal nineteen species, in addition to aquatic invasive plant species or genera that have subsequently been regulated under the Ontario Invasive Species Act (ISA, 2015) which came into force in 2016. This document will present species profile overviews for each of the listed species, with the goal of assisting users in learning how to accurately identify and report sightings, understand more about the species biology and its impacts, and best practices for how to undertake safe and effective control.
The Aquatic Invasive Plant BMP (last updated March 2025) contains identification, lookalikes, biology and life cycle, habitat, distribution, pathways of spread, impacts, and control for the following species:
• Brazilian Waterweed (Egeria densa)
• Curly-leaved Pondweed (Potamogeton crispus)
• European Frog-bit (Hydrocharis morsus-ranae)
• European Lake Sedge (Carex acutiformis)
• European Water Chestnut (Trapa natans)
• Eurasian Water-milfoil (Myriophyllum spicatum)
• Eurasian and Northern Milfoil hybrid (Myriophyllum spicatum × M. sibiricum)
• Fanwort (Cabomba caroliniana)
• Floating Primrose-willow (Ludwigia peploides)*
• Flowering Rush (Butomus umbellatus)
• Hydrilla (Hydrilla verticillata)
• Oxygen Weed (Lagarosiphon major)*
• Parrotfeather (Myriophyllum aquaticum)
• Phragmites (Phragmites australis subsp. australis)
• Purple Loosestrife (Lythrum salicaria)
• Rough Mannagrass (Glyceria maxima)
• Water Ferns – Azolla species (Azolla filiculoides, A. cristata, A. pinnata)
• Water Hyacinth (Eichhornia crassipes)
• Water Lettuce (Pistia stratiotes)
• Watermosses – Salvinia species (Salvinia molesta, S. auriculata, S. minima, S. natans)
• Water Soldier (Stratiotes aloides)
• Yellow Floating Heart (Nymphoides peltata)*
• Yellow Iris (Iris pseudacorus)
(*) – Species is regulated under the Invasive Species Act (ISA) but is not listed on the Ontario Invasive
Aquatic Plant List.
Download the Aquatic BMP below:
