Family name: Cabombaceae
Common names: fanwort, green Cabomba
Category: proposed 1a NEMBA
Aquatic perennial. Stems branched, up to 10 m long. Rhizomes short and fragile. Leaves dark green, submerged, fan-shaped, 7 cm long and 5 cm wide. White flowers, 13 mm in diameter, 3 white sepals and 3 white petals, saucer- shaped white or purple pink. Flowers in summer.
Cabomba caroliniana can be confused with Ranunculus rionii which is widely spread with uncertain invasive status, the differences are mentioned below
Cabomba caroliniana (fanwort):
- Leaves opposite
- Flowers, 3 white sepals and 3 white petals
Ranunculus rionii (water crowfoot):
- Leaves alternate
- Flowers, 5 green sepals and 5-6 white petals
Native to North and South America. Invasive in Australia, United States, Europe and Asia.
History in South Africa
Fanwort was introduced in South Africa via the aquarium trade. It has been recorded at the Berg River, Western Cape and Nahoon River in the Eastern Cape.
Environmental and economic impacts
Fanwort invades rivers, streams and ponds where it becomes rooted in water. Fanwort is an aggressive invader of freshwater systems rich in nutrients and outcompetes the native water plants. It can pose a risk of entanglement and drowning to swimmers. Fanwort will taint and discolour water, increasing the costs of water treatment processes. It blocks foot valves and pumps, increasing maintenance and running costs and reducing pumping efficiencies.
How it spreads
Fanwort spreads via stem fragments, seeds and roots, and subsequently forms dense stands.
How to eradicate
It is difficult to eradicate green Cabomba caroliniana once established. No herbicides are registered for this plant in South Africa
What can you do to help?
Report sightings of these plants to the Early Detection and Rapid Response Programme (EDRR) at SANBI. We will need to know its locality (the exact locality, supply any landmarks or GPS information if possible).
- Invasive species in South Africa. 2010. Cabomba caroliniana. Working for water nursery partnership programme. South Africa. Available online at: http://invasives.org.za/flora-listed-invasives/hydrocleys-nymphoides.html
- Invasive exotic plants in Vermont. 2003. Cabomba caroliniana Gray. Department of conservation, Fish and Wildlife. Recreation of the Vermont Agency of Natural Resources, and The Nature Conservancy of Vermont available online at: http://www.vtfishandwildlife.com/library/factsheets/nongame_and_Natural_Heritage/Invasive_Exotic_Plant_factsheet.pdf
- Martin, G.D and Coetzee, J.A. 2011. Pet stores, aquarists and the internet trade as modes of introduction and spread of invasive macrophytes in South Africa. Department of Zoology and Entomology, Rhodes University. South Africa. Available online at: http://www.ajol.info/index.php/wsa/article/view/68488/56566
- South African Plant Invaders Atlas. 2010. SAPIA News no. 17. ARC-Plant Protection Research Institute. Available on line at: http://www.dargieconservancy.org.za/documents/sapia17.pdf
- South African Plant Invaders Atlas. 2010. SAPIA News no. 09. ARC-Plant Protection Research Institute. Available on line at: http://www.dargieconservancy.org.za/documents/sapia09.pdf