Indian Toothcup, scientifically known as Rotala rotundifolia, is an aquatic and semi-aquatic plant popular in aquascaping. It is known for its adaptability and visual changes based on growing conditions. This plant adds a dynamic element to various water environments, from natural marshlands to cultivated aquatic displays.
Understanding Indian Toothcup
Rotala rotundifolia is a perennial herbaceous plant in the Lythraceae family. It has a creeping growth habit, forming branched stems that create low, dense clumps. The plant’s physical appearance changes considerably based on its environment, especially between its submerged (underwater) and emergent (out-of-water) forms. Common names include Roundleaf Toothcup, Dwarf Rotala, and Pink Baby Tears.
Habitat and Distribution
This aquatic perennial originates from Southeast Asia, including India, China, Japan, Vietnam, Laos, Cambodia, and Myanmar. In its natural habitat, Rotala rotundifolia thrives in moist, shallow water environments like rice paddies, riversides, and other wet locations. The plant has expanded beyond its native distribution, naturalizing in regions like the Southern United States, often introduced through contaminated rice seeds or the aquarium trade. It prefers ample light, from part shade to full sun, and tolerates a wide range of water parameters, including pH levels between 5.5 and 7.5.
Key Identifying Features
Rotala rotundifolia has distinct visual characteristics, especially between its emergent and submerged forms. Emergent plants, growing above the waterline, feature bright-green, rounded leaves less than 2.5 cm long, arranged in opposite pairs. These round leaves give the plant its Latin name, rotundifolia, meaning “round-leaved.” Submerged leaves, found underwater, are narrower, more elongated, and lance-shaped, often appearing darker green, reddish, or even purple, with some varieties showing vibrant pink to fuchsia hues under intense light.
The stems are succulent and often have a pink or purplish tint, branching to form dense growth. Flowers develop on emergent plant tips as small, bright pink to fuchsia blooms arranged in terminal spikes or racemes, appearing in spring and early summer. The plant also forms adventitious roots from stem fragments, allowing it to spread vegetatively.
Ecological Role and Potential Uses
Rotala rotundifolia often grows as a common weed in its native rice paddies. Its rapid growth and ability to form dense mats can shade out other aquatic vegetation and impede water flow in canals where it is introduced.
This species is a popular aquarium plant, valued for its decorative appeal, ease of cultivation, and ability to absorb excess nutrients, which aids in water purification. Its vibrant coloration, from green to pink and red depending on light intensity, makes it a favored choice for aquascaping. While primarily ornamental, Rotala rotundifolia has also been noted for traditional medicinal uses in its native range. Its use in the aquarium trade has led to its introduction as an invasive species in some areas outside its native range.