Common name: Carolina fanwort
Synonyms and Other Names: Cabomba (Portuguese-Brazil), Carolina water-shield, Fanwort, Fish grass, Green Cabomba, Washington grass, Washington-plant
available through www.itis.gov
Identification: C. caroliniana is fully submerged except for occasional floating leaves and emergent flowers (Australian Department of the Environment and Heritage 2003). The roots grow on the bottom of water bodies and the stems can reach the surface. Parts of the plant can survive free-floating for six to eight weeks. It is a perennial, growing from short rhizomes with fibrous roots. The branched stems can grow up to 10m long and are scattered with white or reddish-brown hairs.
The underwater leaves are divided into fine branches, resulting in a feathery fan-like appearance. These leaves are about 5cm across and secrete a gelatinous mucous which covers the submerged parts of the plant. The floating leaves, however, are small, diamond-shaped, entire, and borne on the flowering branches. The solitary flowers are less than 2cm across and range in colour from white to pale yellow and may also include a pink or purplish tinge. The flowers emerge on stalks from the tips of the stems (Australian Department of Environment and Heritage, 2003).
Submersed leaves: petiole to 4 cm; leaf blade 1-3.5 × 1.5-5.5 cm, terminal segments 3-200, linear to slightly spatulate, to 1.8 mm wide. Floating leaves: blade 0.6-3 cm × 1-4 mm, margins entire or notched to sagittate at base. Flowers 6-15 mm diam.; sepals white to purplish [yellow] or with purple-tinged margins, 5-12 × 2-7 mm; petals colored as sepals but with proximal, yellow, nectar-bearing auricles, 4-12 × 2-5 mm, apex broadly obtuse or notched; stamens 3-6, mostly 6; pistils 2-4, mostly 3, divergent at maturity; ovules 3. Fruits 4-7 mm. Seeds 1-3, 1.5-3 × 1-1.5 mm, tubercles in 4 longitudinal rows
The submersed leaves of Cabomba caroliniana are similar in form to those of Limnophila (Scrophulariaceae; introduced in southeastern United States). The latter has whorled leaves in contrast to the opposite leaves of Cabomba .
Size: Mature plant size is approximately 12-31 inches or more (30-80 cm or more) and may grow up to 10m long (Wilson et al. 2007).
Native Range: Cabomba caroliniana A. Gray is native to southern Brazil, Paraguay, Uruguay, northeast Argentina, southern and eastern USA.
Native range in USA: Connecticut, Massachusetts, New Hampshire, Rhode Island, Alabama, Arkansas, District of Columbia, Florida, Illinois, Indiana, Kentucky, Louisiana, Maryland, Michigan, Mississippi, Missouri, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Virgina
Hydrologic Unit Codes (HUCs) Explained
Puerto Rico &
Interactive maps: Point Distribution Maps
Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Cabomba caroliniana are found here.
Table last updated 1/16/2021
† Populations may not be currently present.
* HUCs are not listed for states where the observation(s) cannot be approximated to a HUC (e.g. state centroids or Canadian provinces).
Ecology: Cabomba is sensitive to drying out and requires permanent shallow water, usually less than 3 meters (but up to 10 meters) deep (Australian Department of the Environment and Heritage 2003). It grows rooted in the mud of stagnant to slow flowing water including streams, and smaller rivers (The Washington State Department of Ecology, 2003). It also grows in ponds, lakes, reservoirs, sloughs, ditches, and canals.
It can respond to wide fluctuations in water depths and is a water column feeder that grows well in silty substrate and exhibits reduced vigour in hard substrates. Growth of 50mm a day has been reported in Lake Macdonald in Queensland, Australia. It grows well in high nutrient environments with low pH, but in more alkaline waters it tends to lose its leaves. High calcium levels inhibit growth and unlike other aquatic weeds, cabomba can grow well in turbid water. It prefers a warm, humid climate with a temperature range of 13-27ºC but can survive when the surface of the water body is frozen (Australian Department of Environment and Heritage 2003). PH ranges 4.8~7.8, dCH soft ~ hard.
C. caroliniana flowers from May to September. In the southeastern U.S., C. caroliniana is self-pollinating and seeds readily germinate (The Washington State Department of Ecology 2003).
Means of Introduction: 1935, release from aquarium in Lake Michigan drainage (U.S. EPA 2008). Fanwort stems become brittle in late summer, which causes the plant to break apart, facilitating its distribution and invasion of new waterbodies. It produces seed but vegetative reproduction seems to be its main vehicle for spreading to new waters. 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 area and aquarists (aquarium release or escape) are probably responsible for some introductions.
Status: Established, widely distributed in many US states.
Impact of Introduction: An important aquarium plant.
C. caroliniana is an extremely persistent and competitive plant. In New England and parts of southeast United States, it is sometimes an aggressive weed. It can sometimes form dense growth in water bodies of the southeastern United States and can impede water flow in ditches and canals and interfere with recreational activities (Tarver et al. 1986). Once established, this plant can clog drainage canals and freshwater streams interfering with recreational, agricultural, and aesthetic uses.
In Australia, Cabomba is regarded as a "Weed of National Significance". It is one of the worst weeds in Australia because of its invasiveness, potential for spread, and economic and environmental impacts. It is choking waterways along Australia's east coast (Australian Department of the Environment and Heritage 2003). It is extremely persistent and can take over a water body, excluding native plant species. It can also have an impact on native animals - in northern Queensland platypus and water rat numbers are lower in infested creeks (Australian Department of the Environment and Heritage 2003). Cabomba grows quickly and produces a large amount of plant material. It can significantly reduce water storage capacity and taint drinking water supplies. Water treatment costs can be increased by up to $50 a megalitre (Australian Department of the Environment and Heritage 2003). Heavy infestations can also raise water levels to a point where overflows and heavy seepage losses occur. Cabomba's dense mass of underwater stems and leaves provide a hazard for recreational water users. When this vegetation dies off, decomposition causes dramatic oxygen reductions and foul smelling water.
References: (click for full references)
Australian Department of the Environment and Heritage (ADEH). 2003. Weed Managment Guide: Cabomba- Cabomba caroliniana
. CRC for Australian Weed Managment; Commonwealth Department of the Environment and Heritage. 6 pp.
Bultemeier, B. W., M.D. Netherland, J.A. Ferrell, and W. T. Haller. 2009. Differential herbicide response among three phenotypes of Cabomba caroliniana
. Invasive Plant Science and Management 2(4): 352—359.
CSIRO Entomology. 2011. Biological control of Cabomba. Available http://www.csiro.au/science/ps2ku#a2. Accessed 16 April 2013.
ENSR International. 2005. Rapid Response Plan for Fanwort (Cabomba caroliniana) in Massachusetts. Massachutes Department of Conservation and Recreation. 22 pp.
Ensbey, R. and E. van Oosterhout. 2010. Cabomba. 6 pp.
Falck, M. and S. Garske. 2003. Invasive Non-native Plant Management During 2002. Great Lakes Indian Fish & Wildlife Commission (GLIFWC), Odanah, WI. 68 pp.
Forest Health Staff. 2006. Carolina Fanwort; Cabomba caroliniana Gray. U.S. Department of Agriculture 1 pp.
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.
Global Invasive Species Database. National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG) http://www.issg.org/database/species/ecology.asp?si=402&fr=1&sts=sss
Godfrey, R. K. and J. W. Wooten. 1981. Aquatic and Wetland Plants of Southeastern United States. Dicotyledons. The University of Georgia Press, Athens, Georgia.
Great Lakes Panel on Aquatic Nuisance Species (GLPANS). 2008. Prohibited species in the Great Lakes region. Research Coordination Committee, GLPANS. Available: http://www.glc.org/ans/pdf/08-11-26-Great%20Lakes%20Reg%20Species%20List-complete.pdf
Hamel, K. 2013. Cabomba caroliniana (Fanwort) - Technical Information. Department of Ecology, State of Washington. Available http://www.ecy.wa.gov/programs/wq/plants/weeds/aqua006.html. Accessed 16 April 2013.
Hanlon, C. 1990. A Florida native - Cabomba (fanwort). Aquatics 12(4): 4-6.
Hogsden, K.L., E.P.S. Sager, T.C. Hutchinson. 2007. The impacts of the non-native macrophyte Cabomba caroliniana on littoral biota of Kasshabog Lake, Ontario. Journal of Great Lakes Research 33:497-504.
Hotchkiss, N. 1972. Common Marsh, Underwater and Floating-leaved Plants of the United States and Canada. Dover Publications, Inc., New York.
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Idaho Invasive Species Council Technical Committee, The (IISCTC) . 2007. Idaho Aqautic Nuisance Species Plant. 139 pp.
ITIS (Integrated Taxonomic Information System), 2004. Online Database Cabomba caroliniana. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=18408
Lui, K., M. Butler, M. Allen, E. Snyder, J. da Silva, B. Brownson, and A. Ecclestone. 2010. Field Guide to Aqautic Invasive Species: Identification, collection and reporting of aquatic invasive in Ontario waters. Minstry of Natural Resources, Ontario, Canada. 201 pp.
Madsen, J. D. 1999. A Quantitative Approach to Predict Potential Nonindigenous Aquatic Plant Species Problems. 2 pp.
Marson, D., B. Cudmore, D.A.R. Drake, and N.E. Mandrak. 2009. Summary of a survey of aquarium owners in Canada. Canadian Manuscript Report of Fisheries and Aquatic Sciences 2905: iv + 20 p
Mikulyuk, A. and M. Nault. 2011. Cabomba caroliniana (Carolina fanwort). Available http://www.cabi.org/isc/?aqb=yes&compid=5&dsid=107743&loadmodule=datasheet&page=481&site=144. Accessed 16 April 2013.
Minnesota Department of Natural Resources (MN DNR) 2013a. Grass carp (Ctenopharyngodon idella). Available http://www.dnr.state.mn.us/invasives/aquaticanimals/grasscarp/index.html. Accessed 16 April 2013.
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New York Invasive Species Council (NYISC). 2010. Final report: a regulatory system for non-native species. Department of Environmental Conservation, Albany, NY. 131 pp.
O’Sullivan, C., B. Rounsefell, A. Grinham, W. Clarke, J. Udy. 2010. Anaerobic digestion of harvested aquatic weeds: water hyacinth (Eichhornia crassipes), cabomba (Cabomba caroliniana), and salvinia (Salvinia molesta). Ecological Engineering 36:1459-1468.
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Pennsylvania Department of Conservation and Natural Resources (PA DCNR). 2011. Carolina Fanwort. Cabomba caroliniana A. Gray. 2 pp.
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Shiels, A. L. and M. A. Hartle. n.d. Pond Owner's Guide to the Use of Triploid Grass Carp in Pennsylvania. Pennsylvania Fish & Boat Commission. Available http://fishandboat.com/images/pages/forms/pfbc_tgc002.pdf. Accessed 16 April 2013.
Tarver, D. P., J. A. Rogers, M. J. Mahler, and R. L. Lazor. 1986. Aquatic and Wetland Plants of Florida. Third Edition. Florida Department of Natural Resources, Tallahassee, Florida.
Tilt, K. 2013. Plant Identification Resource: Cabomba caroliniana. Auburn University Horticulture Department. Available http://www.ag.auburn.edu/hort/landscape/dbpages/434.html. Accessed 16 April 2013.
USDA-GRIN (Germplasm Resources Information Network). 2003. Cabomba caroliniana. National Genetic Resources Program [Online Database] National Germplasm Resources Laboratory, Beltsville, Maryland.
U. S. Environmental Protection Agency (U.S. EPA) 2008. Predicting future introductions of nonindigenous species to the Great Lakes. Washington DC. 138 pp.
Washington State Department of Ecology, 2003. Technical Information About Cabomba Caroliniana (Fanwort). Water Quality Program: Non-Native Freshwater Plants.
Wiersema, J. H. 1997. Cabombaceae. In: Flora of North America. Volume 3. Magnoliophyta: Magnoliidae and Hamamelidae. Oxford University Press, Oxford. pp. 78-80.
Wilson, C.E., S.J. Darbyshire, R. Jones. 2007. The biology of invasive alien plants in Canada. 7. Cabomba caroliniana A. Gray. Canadian Journal of Plant Science 87:615-638.
Wisconsin Department of Natural Resources (WI DNR). 2012. Fanwort (Cabomba caroliniana). Available http://dnr.wi.gov/topic/invasives/fact/fanwort.html. Accessed 16 April 2013.
Zhang, X., Z., Yang, and C., Jiakuan. 2003. Fanwort in Eastern China: An Invasive Aquatic Plant and Potential Ecological Consequences. AMBIO: A Journal of the Human Environment, 32:158-159.
USDA/NRCS PLANTS Database
Flora of North America. 2008. efloras.org
For more detailed control information, please view this Rapid Response Guide from the Massachusetts Department of Conservation and Recreation: http://www.mass.gov/dcr/watersupply/lakepond/downloads/rrp/fanwort.pdf
For more information on grass carp, please visit:
Department of Ecology, State of Washington
Michael Porter’s article Controlling Aquatic Vegetation with Grass CarpUS Fish and Wildlife Service Ecological Risk Screening Summary for Cabomba caroliniana
Larson, J. L. Cao, L. Berent, and S. Iott
Revision Date: 7/25/2016
Larson, J. L. Cao, L. Berent, and S. Iott, 2021, Cabomba caroliniana A. Gray: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=231, Revision Date: 7/25/2016, Access Date: 1/17/2021
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.