Roundleaf toothcup, Dwarf rotala
Native to: India and Southeast Asia
Roundleaf toothcup is a popular ornamental in the international aquarium industry that has more recently been promoted for water gardens. It is often referred to as “dwarf rotala” in the trade. It was first collected outside of cultivation in Florida in 1996 from a flood control canal passing through a residential area in Broward County. Other established populations have been found in Palm Beach and Lee Counties. The only other known North American introduction point is Tuscaloosa, Alabama, where it was well-established around a campus pond until the pond was drained and left to dry.
Habit: submersed and emergent freshwater aquatic plant. creeping perennial with soft, dark pink stems that branch often to form low, creeping clumps.
Leaves: rounded and attached closely to the stem without a leaf stalk, arranged oppositely.
Flowers: occur in spikes at the tip of stems, small, bright pink-to-fuchsia.
Fruit/Seeds: dry capsules that split open to disperse seeds.
Distribution in Florida: South Florida
Rotala reproduces both by seed and vegetatively and grows about 4 to 5 inches per week. Once the plant reaches the top of the water, it grows across the surface and quickly shades out other aquatic vegetation. It requires high sunlight and CO2 concentrations for optimum growth. Infests drainage canals and prevents them from emptying rapidly during periods of heavy water load, thus causing flooding. It will also impact navigation when waterways become obstructed.
Do not release from aquariums or use in outdoor settings where it may escape into natural areas.
Because it will root and establish above the waterline, dewatering events (drawdowns) often will not result in complete control.
Most common and frequently used control method. Since this plant spreads by fragmentation, harvested plants should be removed from the site and not simply left to decompose on the bank. Mechanical removal will not commonly provide long-term control.
Grass carp have been observed to show a feeding preference for this plant and may be of limited value to manage this species.
Triclopyr at 1 or 2 ppm provided 100% control of R. rotundifolia. 2,4 D at 1 ppm provided 93% and at 2 ppm provided 99% control. Diquat @ 400 ppb provided 80% control. Endothall, flumioxazin were not effective.
Consult your local UF IFAS Extension for further assistance with management recommendations.