Cabomba caroliniana, commonly known as Carolina fanwort, is a rhizomatous, aquatic, perennial herb native to North and South America. Having been a popular aquarium plant, it has been exported around the world and has become an invasive species in Europe and Australia.
Description
Cabomba caroliniana is a rhizomatous,Cabomba caroliniana in Flora of China @ efloras.org. (n.d.). Retrieved February 14, 2025, from http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=233500297 perennial, aquaticPellegrini, M. O. O. & Jardim Botânico do Rio de Janeiro. (n.d.-b). Cabomba caroliniana A.Gray. Flora E Funga Do Brasil. Retrieved February 13, 2025, from https://floradobrasil.jbrj.gov.br/FB34566 herb. The stems are green, up to long,Northern Territory Government. (n.d.). Cabomba caroliniana A.Gray. FloraNT. Retrieved February 13, 2025, from https://eflora.nt.gov.au/factsheet?id=27617 and wide.Royal Botanic Gardens Victoria. (n.d.-b). Cabomba caroliniana A.Gray. VicFlora Flora of Victoria. Retrieved February 13, 2025, from https://vicflora.rbg.vic.gov.au/flora/taxon/c10eed03-ee28-4e94-80b2-efca95cf0c02 The floating leaves are long and 1–4 mm wide.Cabomba caroliniana in Flora of North America @ efloras.org. (n.d.). Retrieved February 14, 2025, from http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500297
The flower is 0.6–1.5 cm wide and floats on the water surface or extends beyond it.T.D. Stanley, A.E. Orchard, P.G. Kodela. Cabomba caroliniana var. caroliniana, in P.G. Kodela (ed.), Flora of Australia. Australian Biological Resources Study, Department of Climate Change, Energy, the Environment and Water: Canberra. https://profiles.ala.org.au/opus/foa/profile/Cabomba%20caroliniana%20var.%20caroliniana [Date Accessed: 14 February 2025] The sepals are white, long and wide while the petals are white, long and wide. The androecium consists of (3–4–)6 stamens. The gynoecium consists of 2–3 carpels. The fruit is long, wide, and bears ovoid to oblong seeds, which are long and wide.
Cytology The chromosome count is 2n = 26, 78, 104. The chloroplast genome is 164057 bp or 160177 bp long.Gruenstaeudl, M., Gerschler, N., & Borsch, T. (2018). Bioinformatic workflows for generating complete plastid genome sequences—an example from Cabomba (Cabombaceae) in the context of the phylogenomic analysis of the water-lily clade. Life, 8(3), 25.
Similar species Limnophila sessiliflora is similar but has whirls of three or more leaves instead of opposite pairs.
Taxonomy The species was first described by Asa Gray in 1837.Gray, A. (1848). Remarks on the structure and affinities of the order Ceratophyllaceae. Annals of the Lyceum of Natural History of New York, 4(1), 41-50.Cabomba caroliniana A.Gray. (n.d.). Plants of the World Online. Retrieved February 6, 2025, from https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:273581-2 Varieties It has three varieties: Cabomba caroliniana var. caroliniana Cabomba caroliniana var. flavida Cabomba caroliniana var. pulcherrima
Common names Cabomba caroliniana is commonly called Carolina fanwort, Carolina water shield, green cabomba, fanwort, fish grass, Washington grass, Washington plant, common cabomba, Washington plant, and watershield.
Distribution The species is native to southeastern South America (southern Brazil, Paraguay, Uruguay, and northeastern Argentina),Department of Ecology, Washington State: Cabomba caroliniana . Non-Native Invasive Freshwater Plants. Retrieved 16 August 2016 and the East and West Coasts of the United States. Outside of its natural range, it has been introduced to China,Zhang, X., Zhong, Y., & Chen, J. (2003). Fanwort in Eastern China: An Invasive Aquatic Plant and Potential Ecological Consequences. Ambio, 32(2), 158–159. http://www.jstor.org/stable/4315354 Austria, Germany,Landesamt für Natur, Umwelt und Verbraucherschutz Nordrhein-Westfalen. (n.d.). Grüne Cabomba, Karolina-Haarnixe (Cabomba caroliniana). Neobiota in NRW. Retrieved February 25, 2025, from https://neobiota.naturschutzinformationen.nrw.de/neobiota/de/arten/pflanzen/190751/kurzbeschreibung Great Britain, India, Japan, Korea, Malaysia,Malaysia Biodiversity Centre (MBC). (n.d.). Cabomba caroliniana. Malaysia Biodiversity Information System (MyBIS). Retrieved February 25, 2025, from https://www.mybis.gov.my/sp/4448 Netherlands, New Caledonia, New Zealand, Poland, Romania, Sri Lanka, Sweden, and Thailand.
Ecology Large numbers of plants are sent from Florida to the rest of the U.S. for commercial use. Fanwort is also grown commercially in Asia for export to Europe and other parts of the world. Small-scale, local cultivation occurs in some areas, and aquarists are probably responsible for some introductions.
This species grows rooted in the mud of stagnant to slow-flowing water, including streams, smaller rivers, lakes, ponds, sloughs, and ditches. In some states in the U.S., it is now regarded as a weed. Fanwort stems become brittle in late summer, which causes the plant to break apart, facilitating its distribution and invasion of new water bodies. It produces by seed, but vegetative reproduction seems to be its main vehicle for spreading to new waters. Growth of a day has been reported in Lake Macdonald in Queensland, Australia.
Use in the aquarium trade has led to some species being introduced to other parts of the world, such as Australia, where Cabomba caroliniana it is a nationally declared weed. Having arrived in 1967, it spread rapidly in waterways and out-competed native plants, threatening water supplies, especially along the eastern side of the continent. It is a weed of national significance in Australia.
It is also on the list of invasive alien species of concern in the European Union. The latter implies that the species cannot be traded nor commercialised. The EU forbids trading and selling of the plant and requires people possessing it before the regulation went into force to take appropriate measures to prevent it from spreading. Control measures a trial is under way to control the weed by introducing a tiny South American beetle, Hydrotimetes natans, or Cabomba weevil, into Lake Macdonald and Lake Kurwongbah in Queensland. The species is being bred in a nursery at Kurwongbah, with a view to national introduction for biological control of the weed. The larvae of the weevil damage the plant by tunnelling through its stems, breaking them down and causing fungal infections which hinder their ability to reproduce. It has been found that only the insect mostly feeds on Cabomba, and does not affect any native plants.
Conservation The NatureServe conservation status is G5 Secure.
References
Further reading Ørgaard, M. (1991). The genus Cabomba (Cabombaceae) - a taxonomic study. Nordic Journal of Botany 11: 179-203 Gleason, H.A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York. Hotchkiss, N. 1972. Common Marsh, Underwater and Floating-leaved Plants of the United States and Canada. Dover Publications, Inc., New York. Radford, A.E., H.E. Ahles, and C.R. Bell. 1968. Vascular Flora of the Carolinas. The University of North Carolina Press, Chapel Hill. Riemer, D.N. and R.D. Ilnicki. 1968. Overwintering of Cabomba in New Jersey. Weed Science 16:101-102.
External links Tropica Center for Aquatic and Invasive Plants Fanwort invasion in Washington waters Age of Aquariums Missouri plants