Nymphaea nouchali, known as red and blue water-lily, blue star water-lily, or star lotus, is an aquatic flowering plant in the Nymphaceae (water-lily family), native to southern and eastern Asia (including the Indian subcontinent, China, and Taiwan), Borneo, the Philippines, Sri Lanka, and Australia, where it typically grows in ponds. It is often called the “blue lotus of India,” but it is not a true lotus (of the lotus family, Nelumbaceae; the genus Lotus is in the legume family, Fabaceae), nor are water-lilies true lilies (of the family Liliaceae).

N. nouchali grows from rhizomes or tubers rooted under the water. Leaves are oval to round, 13–15 cm (5–6 in), with an open sinus at the leaf base where it attaches to the petiole (leaf stem). Leaves may spread 1.4–1.5 m (4–5 feet) from where the rhizome is rooted. Flowers, which have little fragrance, are stellate (star-shaped) with 4 sepals and 10–16 petals, and are 5–13 cm (2–5 in) in diameter. Although leaves float on the water surface, flowers are generally held 30 cm (12 in) above water. They are usually pale blue (but can be pink or white) with pale yellow stamens and anthers.

N. nouchali has been cultivated in southeast Asia for centuries, especially around temples. It is also cultivated in Sri Lanka and gathered from dried ponds in India for the rhizomes, which are used as food and animal fodder as a source of starch. In Ayurvedic medicine, it is used to treat indigestion.

Cultivars include N. nouchali var. cyanea, which has medium-sized pale to deep blue flowers, and N. nouchali var. versicolor, which is commonly exported in the form of tubers from Sri Lanka to Europe and the U.S. for use in the aquariums; the tubers grow quickly after exposure to warm water, making an “instant” aquarium plant.

(Everett 1981, FOC 2011, Slocum 2005, Wikipedia 2011)