European Frog-Bit (Hydrocharis morsus-ranae)

If you think you have seen European Frog-Bit, use the Identifying features and similar species section to verify.

On this page

• Identifying features and similar species
• Origin and current distribution
• Habitat
• Pathways of introduction and spread
• Impacts
  • Ecological impacts
  • Socioeconomic impacts
• Government action
  • Prevention and management
• What can you do
• Related links

Identifying features and similar species

Identifying features of the European Frog-Bit

• non-rooted floating plant
• heart or bean-shaped leaves about 1.5 to 6.5 cm long
• leaves are attached on long petioles and arranged in rosettes connected by runners below the surface of the water
• underside of leaves are purple and covered with a spongy layer
• flowers are composed of 3 pinkish white petals and a yellow center (pistil and stamens)

Similar species

European Frog-Bit can be distinguished from similar species by its white 3-petaled flowers and heart- or bean-shaped leaves measuring from 1.5 to 6.5 cm. In addition, unlike other floating plants, it has no stem and it doesn't take root at the bottom of water bodies.

It is possible to confuse it with other invasive species, such as Yellow Floating-Heart.

European Frog-Bit can also resemble several aquatic plants that are naturally found in some Canadian waterbodies, including:

• Little Floating-Heart
• Native Water-Lilies
• Fragrant Water-Lily

These species are naturally found in Quebec and Ontario, but they may also be found in other parts of Canada.

Little Floating-Heart (Nymphoides cordata)

Little Floating-Heart is distinguished from the European Frog-Bit mainly by its emerging white five-petaled flowers and the small banana-like tubers growing from its stem. In addition, this plant is rooted to the sediments.

Native Water-Lilies (Nuphar spp. and Nymphea spp.)

European Frog-Bit can easily be mistaken for Water-Lilies (Nuphar spp., Nymphaea spp.), which are also floating plants. In Canada, there are at least 5 species of Nuphar and 7 species of Nymphea. They can be distinguished from the European Frog-Bit by the number of petals on their flowers: Nymphea have at least eight petals while Nuphar have between 4 and 6 petals, unlike European Frog-Bit that have three.

Yellow Pond-Lily can be distinguished from European Frog-Bit mainly by their oval leaves, 7 to 40 cm long, D-shaped stems and their yellow ball-shaped flowers, with 5 to 6 petals.

Fragrant Water-Lily (Nymphaea odorata)

The Fragrant Water-Lily is mainly distinguished from the European Frog-Bit by its round leaves, measuring between 10 and 30 cm in diameter, green on top and reddish-purple underneath, and by its long, round and flexible stem. Additionally, the Fragrant Water-Lily has large white flowers measuring between 7 and 10 cm in diameter.

If you think you have seen European Frog-Bit or another AIS, contact us to report it.

Origin and current distribution

European Frog-Bit, also known as Common Frog-Bit, is a perennial plant native to Europe and parts of Africa and Asia.

It was introduced to North America in the early 1930s for use as an ornamental plant in water gardens. It is now found in several American states, including New York. In Canada, this small plant was first introduced in 1932 to experimental ponds in Ottawa to assess its ornamental potential. It was then found in the Rideau Canal in 1939, invading the Ottawa River, the St. Lawrence River, the Richelieu River and Lac Saint-Jean. It is also present in Lake Ontario and Lake Erie.

Habitat

European Frog-Bit thrives in calm, nutrient-rich waters. It is found in shallow sections of lakes and rivers, as well as in ponds, marshes, and ditches. It is limited by specific conditions, such as a pH between 6.5 and 7.8 and cannot survive prolonged freezing. This plant grows rapidly to form dense floating mats. The plant buds are submerged in late autumn and rise to the invaded water bodies' surface around the end of winter with new plants emerging the following spring. It can also multiply by stem fragments taking root.

Pathways of introduction and spread

European Frog-Bit is mainly introduced into new bodies of water through human activities, such as the aquarium and water garden trade, or accidental transport by watercraft. It uses vegetative reproduction (asexual reproduction) by producing clones that can survive harsh conditions. Its spread is facilitated by human activities and could increase with the presence of excessive nutrients in lakes. It can also be moved by currents, by abundant rainfall causing flooding, and by clinging to wildlife or other aquatic plants.

Impacts

Ecological impacts

European Frog-Bit is a fast-growing plant. It develops in large colonies forming thick mats of vegetation that reduce the biodiversity of native plants, smothering them and preventing sunlight from reaching submerged plants. They deteriorate habitats for native fish and wildlife by creating stagnant water and causing a drop in oxygen levels, thus altering water quality and affecting aquatic fauna such as fishes and benthic macroinvertebrates (animal lacking a backbone and large enough to see without the aid of a microscope found on the bottom, or in the bottom sediments, of a sea or lake).

Socioeconomic impacts

By interfering with recreational activities such as boating, fishing, and swimming, the presence of European Frog-Bit mats in a body of water can adversely affect waterfront property values and negatively impact tourism. The costs associated with controlling and eradicating the plant can also be high.

For more information on the impacts of invasive plants, consult the threats to the environment, the economy, and society.

Government action

Prevention and management

Preventing its introduction and spread is the best way to control this invasive plant.

There are various ways to control invasive aquatic plants:

• physical or mechanical removal (by hand, with tools or machinery)
• dewatering (lowering water level)
• tarping (covering with opaque material to limit growth)
• herbicide application

Control measures vary depending on the species, so you must take precautions before attempting to control an AIS to avoid it spreading further. If you wish to undertake a project to control aquatic invasive species, contact the department to ensure that you meet the requirements of the laws and regulations protecting aquatic environments in your region.

What can you do

Once an AIS has become established in a lake or watercourse, it is difficult and costly to control and almost impossible to eradicate. Preventing its introduction and spread is the best way to combat it. Simple but effective actions can make a difference to protecting water bodies:

• learn to recognize AIS and report their presence
• always clean, drain and dry your watercraft and gear after leaving a body of water. Follow the cleaning steps described on Clean, Drain, Dry and Decontaminate
• avoid boating through beds of invasive aquatic plants so as not to contribute to their spread. Buoys can be installed (PDF, 987 KB) to mark the main AIS beds and restrict traffic
• don’t let loose any plant remains, water, or organisms from your water garden or aquarium into the natural environment

Learn more about preventing aquatic invasive species.

Related links

• Identification booklet of freshwater invasive plant species in Quebec
• Fact sheets to identify invasive aquatic plants and distinguish them from similar species: European Frog-Bit (PDF, 808 KB) (French only)
• European Frog-bit – Profile and Resources | Invasive Species Centre
• European Frogbit - Alberta Invasive Species Council
• Field Guide to Aquatic Invasive Species for British Columbia (PDF, 6.0 MB)