Bacopa is a genus of about 70 to 100 aquatic plants known as water hyssops or water purslanes. Two are commonly grown as garden plants. Extracts of Bacopa monnieri are used in Ayurvedic medicine and may have wider medicinal uses. The common name bacopa is also used to refer to the unrelated southern African species Chaenostoma cordata, which has similar flowers but is not aquatic in habit and does not have the succulent leaves of the true bacopas.
Plants of the bacopa genus have small, opposite, succulent leaves and creeping or semi-erect stems. B. monnieri bears small white, blue or pink flowers with four or five petals. B. caroliniana has blue flowers, slightly hairy upper stems and the crushed leaves have a distinctive, lemony smell. Bacopa plants can grow to be 3 feet across and 1 foot high. Both of the commonly grown species are perennials in frost-free zones.
B. monnieri is an Asian species found in Nepal and India through Vietnam and into China, and also on Sri Lanka and Taiwan. It has become naturalized in Florida and other southern states. B. caroliniana is native to the southern part of the United States. Other bacopa species are found throughout the tropical and subtropical world with several native to the U.S.
Bacopas are found in both running and still water and will even grow in brackish conditions. They need constant moisture and will even grow completely underwater in slow moving streams, ponds and lakes. Bacopas are not frost-tolerant and will die back completely in colder climates.
Plant bacopas in damp soil close to water, around a water feature or in the shallow sections of a pond. They thrive in full sunlight or high shade but may become straggly and not flower in partial shade. Bacopas can also be grown as a trailing container plant provided that they are well watered. An application of general purpose fertilizer every two weeks during the growing season is plenty, reduced down to every month during the rest of the year. Propagation is by cuttings, which can easily be rooted in damp compost or in a container of water provided that they are kept humid and warm. In frost zones, 8-inch stem cuttings can be brought indoors and winterized on a sunny windowsill with their ends in a jar of water.
Both of the commonly cultivated bacopas and several other species are used as aquarium plants thanks to their ability to grow completely underwater. The leaves of B. monnieri are used as a tender vegetable in Vietnamese cuisine. In Ayurvedic medicine B. monnieri is known as brahmi, and is used to treat asthma and in high doses, epilepsy. It is also believed to enhance cognitive function and memory. Bacopa plants are high in antioxidants and human trials have shown that an extract of the plant reduces the rate at which new information stored in the brain is lost.