The leaves of Camellia sinensis are dried to make the tea we drink; the genus name commemorates Georg Josef Kamel (1661–1706), a Jesuit pharmacist born in Moravia (Czech Republic). He went as a Jesuit priest to the Marianas in 1683 and Manila in the Philippines in 1688, and set up the first pharmacy there. He sent plants found in the gardens of the Chinese to the botanist John Ray (1627–1705) in England, who published his work in an appendix to his own Historia plantarum (1686–1704) as Herbarum aliarumque stirpium in insula Luzone Philippinarum (1704) (Herbs and other plants in the island of Luzon in the Phillipines). It is unlikely that Kamel found camellias as he never went to Japan or China, but his work on the flora of the Far East was substantial, and merited the recognition. He also wrote Observationes de avibus Philippensibus (1702), the first account of the birds of the Philippines.

The evergreen Camellia sinensis is a frost-hardy shrub in the Theaceae family. It comes from west China, where summers are warm and wet and winters are dry and frost-free. In the Medicinal Garden it grows in a sheltered position in partial shade; dainty white, scented flowers appear in autumn and winter. It prefers rich, acidic soil, so plenty of organic matter was incorporated on planting, and during the growing season it is fed monthly with an organic, seaweed-based, fertiliser.(by Clare Beacham)

Camellia sinensis. Caffeine and theophylline. Coffea arabica. When the habits of drinking tea made from C. sinensis leaves, and coffee made from berries of Coffea arabica became established in Europe in the 17th century, it was soon realised that they could cause the production of more urine than the volume drunk. It took more than 200 years to understand that both contained simple chemicals Theophylline and Caffeine that acted on the kidney to increasing the production of urine, diuresis. This used to be medically important because the effect could be used to treat diseases arising from failure of normal control of the water in the body such as in heart failure. Nowadays other, more powerful diuretics are available and both drinks are enjoyed for other reasons.

Prescription only medicine: Theophylline. A concentrated Green Tea Extract taken by mouth as a slimming aid has been proposed but it has caused liver damage in some subjects and is not now considered safe. An ointment containing 10% of a particular green tea extract has been approved as an effective prescription treatment for genital warts. Its principal adverse effect is irritation of the skin around the site of application. The mechanism of this activity is not known.

Potential mood altering, anti-cancer and anti-infective activities of tea preparations and isolated chemical constituents are reviewed

Tea was first brought to Europe in 1610 and by 1750 had become the British national drink, with 18,000 tonnes imported annually. It remained a monopoly for the Chinese until the beginning of the 19th century when Dr Siebold (qv under Primula sieboldii) smuggled seeds to Java to set up tea growing there. In 1848 and subsequent years, the British plant hunter Robert Fortune (1812–89) smuggled 100,000 tea plants and seedlings to Darjeeling, India, accompanied by Chinese tea growers, for the East India Company, and set up the Indian tea plantations. Fortune not only used the Wardian cases – watertight boxes with glass tops – for shipping plants, but also sowed seed into earth in the cases and these germinated in transit, ready for planting out on arrival (Cox, 1945).

Only marginally hardy, this small shrub seems happy in the Medicinal Garden. The leaves are the source of tea, drunk principally for its stimulating effect. This is due mainly to its caffeine content with small amounts of theophylline and theobromine. The dry leaf contains more caffeine than coffee, but less of it by weight is used in making a cup, so tea as a beverage is less stimulating. The various different types of tea – black, green and white – have their different fl avours due solely to the preparation method and the quality of the leaf. It was unknown to the 16th-century herbalists, coming as it did from China. Tea was first brought to Europe in 1610 and by 1750 had become the British national drink with 18,000 tonnes imported annually. Worldwide, 3.5 million tonnes of tea are now harvested annually.

Current agronomic aspects of the tea industry, genomic studies, attempts at genetic manipulation of tea plants and effects of environment on growth and composition of tea are reviewed

Brief review of current knowledge of epicatechin gallate, theanine, caffeine and other chemical constituents and of relevant genetics.

Contains Quercetin, a Flavonoid. Not carcinogenic but is genotoxic.