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| NAS - Nonindigenous Aquatic Species |
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Common Name: Carolina fanwort
Synonyms and Other Names: Cabomba (Portuguese-Brazil), Carolina water-shield, Fanwort, Fish grass, Green Cabomba, Washington grass, Washington-plant
Taxonomy: available through 
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).
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
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Interactive maps: Continental US, Alaska, Hawaii, Caribbean
Nonindigenous Occurrences:
This plant has been dispersed throughout the world by the aquarium trade and is naturalized in Peru, China, India, Japan, Malaysia, the south east of the USA and parts of Australia and Canada (USDA-GRIN 2003).
Great Lakes region: The first sighting in the Great Lakes drainage was in the Lake Michigan drainage in 1935. Reported for IL, IN, MI, NY, OH, PA and Ontario
Other US Reports: Ala., Ark., Conn., D.C., Fla., Ga., Ky., La., Md., Mass., Miss., Mo., N.H., N.J., N.C., Okla., Oreg., R.I., S.C., Tenn., Tex., Va
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: 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.
Remarks: In parts of the southeastern United States, plants with purple-tinted flowers, possibly a response to some environmental factor, have been treated as Cabomba caroliniana var. pulcherrima. South American plants with yellow flowers have been called C . caroliniana var. flavida O/rgaard.
References
Australian Department of the Environment and Heritage, 2003. Cabomba (Cabomba caroliniana). Weeds of National Significance: Weed Management Guide Department of the Environment and Heritage and the CRC for Australian Weed Management.
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.
Hanlon, C. 1990. A Florida native - Cabomba (fanwort). Aquatics 12(4): 4-6.
Hotchkiss, N. 1972. Common Marsh, Underwater and Floating-leaved Plants of the United States and Canada. Dover Publications, Inc., New York.
ITIS (Integrated Taxonomic Information System), 2004. Online Database Cabomba caroliniana.http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=18408
Ørgaard, M. 1991. The genus Cabomba (Cabombaceae) - a taxonomic study. Nordic Journal of Botany 11: 179-203
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.
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.
USDA-GRIN (Germplasm Resources Information Network). 2003. Cabomba caroliniana. National Genetic Resources Program [Online Database] National Germplasm Resources Laboratory, Beltsville, Maryland.
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.
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.
Other Resources:
USDA/NRCS PLANTS Database
Flora of North America. 2008. efloras.org
Author: Ling Cao
Contributing Agencies: 
NOAA - GLERL
Revision Date: 10/2/2007 Citation for this information:
Ling Cao. 2009. Cabomba caroliniana. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.
<http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=231> Revision Date: 10/2/2007
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