Carolina Fanwort (Cabomba caroliniana)

If you think you have seen Carolina Fanwort, 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 Carolina Fanwort

• submerged plant that takes root in the sediments
• submerged, fine, fan-shaped leaves, each 5 to 6 cm wide
• occasionally has small floating leaves, oblong, up to 1.3 cm in length
• small solitary flowers (0.6 to 1.5 cm) that are white or pale-yellow in color
• flowers with 3 petals and 3 sepals that are similar in size and color to the petals
• stems that are divided into several branches, sometimes covered in reddish-brown hairs or slimy gelatin

Similar species

The Carolina Fanwort can be distinguished from similar species by its stems, which are divided into several branches and sometimes covered in reddish-brown hairs or slimy gelatin.

The Carolina Fanwort can be confused with 2 other invasive species, Eurasian Water-Milfoil and Parrot’s Feather.

In addition, the Carolina Fanwort resembles several aquatic plants that are naturally found in waterbodies among various regions across Canada, including:

• Common Bladderworts
• Beck’s Water-Marigold
• Hornworts
• native Water-Milfoils
• White Water Buttercup

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

Common Bladderwort (Utricularia vulgaris)

The Common Bladderwort can be distinguished from the Carolina Fanwort by its yellow flowers and emerging fruits, as well as the presence of modified leaves in the form of small sacs (utricles) on the submerged parts of the plant, which allow it to float and catch insects, small crustaceans, or aquatic larvae.

Beck’s Water-Marigold (Bidens beckii)

Beck’s Water-Marigold can be distinguished from Carolina Fanwort by its yellow flowers and strongly toothed emerging leaves. In addition, its submerged, sharply divided leaves are further apart than those of the Carolina Fanwort.

Hornwort (Ceratophyllum spp.)

Hornwort can be distinguished from the Carolina Fanwort by their whorled leaves, i.e. arranged around a point on the stem, and subdivided with spines on their margins, as well as small fruits at their base. In addition, their leaves are rigid and retain their shape out of the water.

Native Water-Milfoil (Myriophyllum spp.)

It is possible to distinguish the Carolina Fanwort from other Water-Milfoils species that occur naturally in our bodies of water. However, this can generally only be done by experts. They will look to see whether:

• the flowers are in spikes or at the leaf insertion point on the stem
• count the number of leaves in whorls (grouped around a point on the stem)
• the number of pairs of leaflets (small compound leaves) that look like feathers

White Water Buttercup (Ranunculus aquatilis)

White Water Buttercup can be distinguished from Carolina Fanwort by their floating leaves with 3 to 5 main lobes and their single white flower with 5 petals.

If you think you have seen Carolina fanwort or another AIS, contact us to report it.

Origin and current distribution

Carolina Fanwort is native to the southeastern United States and parts of South America.

It was first reported in central Ontario (Lake Kasshabog, Crowe River) in 1991 and has since spread to the northeastern United States. It has also been reported in Halifax, Nova-Scotia.

Habitat

Carolina Fanwort thrives in the slow-moving or still waters of small rivers, ditches, ponds, and lakes, in water less than 3 metres deep. This plant can rapidly grow and form dense mats under or on the surface of the water. It multiplies by fragments of stems or rhizomes that can form new plants. Tolerant of cold water, it can remain green all year round.

Pathways of introduction and spread

As a popular aquarium plant, Carolina Fanwort was likely introduced from the release of aquarium plant matter or water in the natural environment and its spread is likely due to biofouling (the formation of a disturbing layer of living organisms on an artificial surface in permanent or frequent contact with water) on watercraft. Once introduced, the Carolina Fanwort can establish itself and spread thanks to its ability to reproduce by fragmentation and by seed. It can migrate with currents, be dispersed by rain-causing flooding, and attach itself to wildlife or other aquatic plants.

The Carolina Fanwort can be easily spread by boats or other equipment that disperse stem fragments in new areas. Because of its persistence and potential for spread, it is a very difficult plant to control.

Impacts

Ecological impacts

The Carolina Fanwort is a fast-growing plant, forming thick mats of vegetation that compete with and crowd out native plants. This invasive plant prevents light from entering the water, harming submerged plants and disrupting fish communities.

Its presence in a watercourse reduces the current and obstructs drainage channels and water pipes. It impedes water-based recreational activities such as swimming, boating, and fishing. The decomposition of the abundant plant mats contributes to reduced oxygen levels in the water, which is detrimental to the survival of fish and other aquatic organisms, and can lead to excessive nutrients in the water.

Socioeconomic impacts

By interfering with recreational activities such as boating, fishing, and swimming, the presence of Carolina Fanwort in a body of water can adversely affect the value of waterfront properties and harm tourism. The costs associated with controlling and eradicating the plant can also be high, as can the costs associated with blocked irrigation canals.

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: Carolina Fanwort (PDF, 814 KB) (French only)
• Fanwort – Profile and Resources | Invasive Species Centre
• Fanwort - Alberta Invasive Species Council
• Field Guide to Aquatic Invasive Species for British Columbia (PDF, 6.1 MB)