Cabomba caroliniana
Popular aquarium plant turned invasive in Europe and Australia.
Cabomba caroliniana, called Carolina fanwort or green cabomba, is a perennial aquatic herb that spreads via rhizomes. It is native to parts of North and South America. Because it became a popular aquarium plant, it was shipped worldwide and is now an invasive species in Europe and Australia.
The plant has green stems that can grow up to 1.5 meters long and are 1–2 millimeters wide. Its floating leaves measure 0.6–3 centimeters long and 1–4 millimeters wide. Flowers are 0.6–1.5 centimeters wide and either float on the water or rise above it. Sepals are white, 5–12 millimeters long and 2–7 millimeters wide; petals are also white, 4–12 millimeters long and 2–5 millimeters wide. The androecium has (3–4–)6 stamens, and the gynoecium consists of 2–3 carpels. Fruits are 8–8.7 millimeters long and 2.1–2.3 millimeters wide, containing ovoid to oblong seeds that are 1.5–3 millimeters long and 1–2.2 millimeters wide.
The chromosome count is 2n = 26, 78, or 104, and the chloroplast genome is either 164,057 or 160,177 base pairs long. A similar species, *Limnophila sessiliflora*, can be told apart by its whorls of three or more leaves rather than opposite pairs.
Asa Gray first described the species in 1837. It has three varieties: *Cabomba caroliniana* var. *caroliniana*, *Cabomba caroliniana* var. *flavida*, and *Cabomba caroliniana* var. *pulcherrima*. Common names include Carolina fanwort, Carolina water shield, green cabomba, fanwort, fish grass, Washington grass, Washington plant, common cabomba, and watershield.
The plant is native to southeastern South America (southern Brazil, Paraguay, Uruguay, and northeastern Argentina) and the East and West Coasts of the United States. Outside its natural range, it has been introduced to China, Austria, Germany, Great Britain, India, Japan, Korea, Malaysia, Netherlands, New Caledonia, New Zealand, Poland, Romania, Sri Lanka, Sweden, and Thailand.
Large numbers of plants are shipped 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 regions. Small-scale local cultivation occurs in some areas, and aquarists likely cause some introductions. This species grows rooted in mud in stagnant to slow-flowing water—streams, smaller rivers, lakes, ponds, sloughs, and ditches. In some U.S. states, it is now considered a weed.
Quick Facts
- Genus
- Cabomba
- Species
- caroliniana
Facts from the source article.
Lore & Background
Cabomba caroliniana was first described by Asa Gray in 1837. It has three varieties: Cabomba caroliniana var. caroliniana, var. flavida, and var. pulcherrima. The species is native to southeastern South America and the East and West Coasts of the United States. Outside its natural range, it has been introduced to many countries including China, Japan, Australia, and several European nations. Large numbers of plants are sent from Florida for commercial use, and it is also grown commercially in Asia for export. The plant grows rooted in mud of stagnant to slow-flowing water such as streams, lakes, ponds, and ditches. Fanwort stems become brittle in late summer, causing the plant to break apart and facilitating its spread. Growth of 50 mm per day has been reported in Lake Macdonald, Queensland, Australia.
Reader's Guide
Cabomba caroliniana is notable primarily for its dual role as a popular aquarium plant and a serious invasive species. The article states that use in the aquarium trade has led to introductions worldwide, and in Australia it is a nationally declared weed. Having arrived in 1967, it spread rapidly in waterways, out-competing native plants and threatening water supplies, especially along the eastern side of the continent. It is also on the list of invasive alien species of concern in the European Union, which forbids trading and selling of the plant and requires measures to prevent its spread. As of July 2023, a trial is under way in Queensland to control the weed by introducing a tiny South American beetle, Hydrotimetes natans (Cabomba weevil), whose larvae tunnel through stems, causing fungal infections that hinder reproduction. The beetle has been found to feed mostly on Cabomba and does not affect native plants. The species is also grown commercially in Asia for export, and small-scale local cultivation occurs in some areas, with aquarists probably responsible for some introductions.
Did You Know?
- It has three varieties: var. caroliniana, var. flavida, and var. pulcherrima.
- A trial using the Cabomba weevil (Hydrotimetes natans) for biological control began in July 2023 in Queensland.
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