Called “dimorphic” for its two different types of leaves (one submerged and one floating on the water’s surface), these are rapidly growing and fast reproducing plants at home in freshwater climates. They grow fairly tall with a great deal to spread due to propagation by fragmentation. They are sometimes used to prevent algae from growing in ponds, although they can become invasive in select areas.
Cabomba caroliniana (Fanwort, Carolina watershield)
Hardiness Zones: 6-10
Height: The stems grow up to 1.8 meters (6 feet) long.
Diameter: 30-90 centimeter (12-36 inch) spread
Growth Rate: fast, invasive in some areas (can grow up to 5 centimeters (2 inches) in one day)
Age: perennial, grown as an annual in select areas
Root System: fibrous, silver-colored
Subspecies: var. pulcherrima, var. caroliniana
Tolerates: slow-moving waters
Problems (major): no major insect/disease problems, spreads very aggressively
Problems (minor): Grass Carp may prey on these.
Poisonous: presumably no
Soil requirements: very wet soil, muddy
Air requirements: not sufficiently researched
Watering requirement: survives in entirely drenched areas
Sun requirement: full sun
Depth: prefers water less than 3 meters (10 feet) deep
Freshwater/Saltwater native: freshwater
Location (Pond, Stream, River, Lake, Sea, Ocean): marshes, rivers, lakes, streams, ponds, resovoirs, canals, acidic (preferred) or alkaline water
Colonization: spreads by fragmentation and vegetative propagation
Motility: minimal to none
Nautical reproductive cycle: reproduces either by fragmentation or seed production
Alternation of isomorphic/heteromorphic generations: isomorphic
Leaf shape: bright green, feathery foliage underwater – light green, lily pad-like, triangular leaves above the water (infrequent)
Leaf size: 3-7 centimeter long underwater foliage, 2 centimeter wide lilypad-like leaves float on the surface
Flower structure: white-purple-or-pink flowers up to 1/2 inches in diameter
Flowering frequency: flowers May-September
Annual/Biennial/Perennial: perennial, typically grown as an annual
The most unique feature of C. caroliniana is the dimorphic nature of its foliage, producing one type of “leaf” underwater and one above water.
Sometimes grown as an ornamental, these keep water clear and algae from appearing.
A Fanwort with its stem and underwater foliage visible (uploaded 19 September 2010 by Show Ryu)
Fanwort art displaying the various “parts” (organs) (Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner’s Sons, New York. Vol. 2: 76. Courtesy of Kentucky Native Plant Society. Scanned by Omnitek Inc.)
I do not own the rights of these images; all credit goes to its original creator(s).