Geography and distribution
The origin of tea is not clear. Camellia sinensis var. sinensis is probably native to western Yunnan, while C. sinensis var. assamica is native to the warmer parts of Assam (India), Burma, Thailand, Laos, Cambodia, Vietnam and southern China. 'Wild' tea plants can be found growing in forests, but these may be relics of past cultivation.
Overview: An evergreen shrub, which can grow up to 17 m high. In cultivation, it is usually kept below 2 m high by pruning.
Leaves of Camellia sinensis
Leaves: Bright green, shiny, often with a hairy underside.
Flowers: Scented, occurring singly or in clusters of two to four.
Fruits: Brownish-green, containing one to four spherical or flattened seeds.
Camellia sinensis var. sinensis is hardier than Assam tea, and has relatively small and narrow leaves. Its leaves are used to produce green tea and China black tea.
C. sinensis var. assamica is much taller in its natural state (than when cultivated) and can grow into a loosely branched tree to a height of about 17 m. It is a less hardy variety with larger, rather droopy, leathery leaves, which are used to make Assam (Indian) black tea.
Threats and conservation
It is not clear whether a truly 'wild' Camellia sinensis plant still exists.
Camellia sinensis has been considered an invasive pest species in a nature reserve in Tanzania. There are also reports of it spreading into Madagascan forests where it may have detrimental effects on the regeneration of native forests which are important lemur habitats.
Early uses of tea in China
In China, tea has been used as a medicinal infusion, for chewing and as a pickle for over 4,000 years. There is written evidence from the T'ang dynasty in AD 650 that tea was being cultivated in most of the provinces of China and that the process of making tea was well established.
Tea in Japan
Tea was introduced into Japan in about 600 AD by Buddhist priests returning home after studying in China. During the 8th and 9th centuries its use was widespread in courtly and monastic circles and a tea culture developed. By the 1330s onwards, all Japanese social classes drank tea.
Tea and social interaction
Harvesting Camellia sinensis in Vietnam
It is has been suggested that tea spread so quickly, and was absorbed into so many different cultures, because of the way it is served - its preparation gives the chance for social interaction and the development of elaborate ceremonies. By the early 1800s, in the heyday of the East India Company, Britain was drinking its way through nine million cups of tea a year. Today, in Britain alone 165 million cups of tea are drunk a day, which equates to 62 billion cups a year; over three million tonnes of tea are produced annually, with India being the largest tea producing country, growing nearly 30% of the world’s tea.
In China, the medicinal effects of tea have a history dating back almost 5,000 years. The use of tea in traditional Chinese medicine is well documented and it is suggested that it could be used as a cure for over 200 illnesses.
Tea is not an important medicine in the main medical traditions of South Asia. Medicinally, tea has been most used as a stimulant, as an astringent lotion which may be used as a gargle or injection, for some digestive problems and to reduce sweating in fevers. In Tamil Nadu, tea leaves have been used homeopathically for mania, paralysis, nervousness, neuralgia and sleeplessness.
Tea's stimulant effects are caused by xanthines such as caffeine. Caffeine is included in small doses in some over-the-counter medicines for its stimulant effect, and is often combined with medicines that treat pain, such as aspirin. An infusion of tea leaves was once used as a remedy for insect bites.
Too much tea?
Compressed tea flowers (Exposition Hanoi 1902) from Kew's Economic Botany Collection
Excessive intake of caffeine can cause headaches and anxiety. Regular consumption of large amounts of caffeine, aminophylline or theophylline by breastfeeding mothers can cause irritability and poor sleeping patterns in the infant.
Drinking large amounts of theophylline and aminophylline can cause many side effects, including heart problems such as palpitations, sickness, insomnia and convulsions. Toxic effects are more likely to occur when theophylline and aminophylline are taken at high doses or together with certain other medicines.
It has been reported that there may be some link between cancer of the oesophagus and excessive tea drinking and the resulting high consumption of condensed tannin compounds. Drinking tea may have diuretic effects, largely due to the caffeine, and tea may also inhibit the absorption of iron in the gut.
Active compounds in tea
The last decade has seen huge interest in tea's medicinal properties. Tea contains the compound theophylline, which is used in a licensed medicine for the treatment of respiratory diseases such as asthma.
Tea also contains flavonoids, compounds reported to have anti-oxidant properties and which may be beneficial to health, such as in the prevention of heart disease and cancer. Tea flavonoids are also reported to reduce inflammation and to have antimicrobial effects.
Some studies suggest that tea may help prevent tooth decay. Tea is also used in some cosmetic products for its astringent effect. The chemical composition of tea may vary depending on a number of factors, such as the conditions in which the plant is grown and how the leaves are processed.
Millennium Seed Bank: Seed storage
The Millennium Seed Bank Partnership aims to save plant life worldwide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in our seed bank vault.
Two collections of Camellia sinensis seeds are held in Kew’s Millennium Seed Bank based at Wakehurst in West Sussex.
See Kew’s Seed Information Database for further information on Camellia sinensis seeds
Tea has been grown from seed at Kew, as well as being brought in as young plants. The tea bushes growing outside in the Woodland Glade were planted in 1992 and have proved to be hardy, surviving snow and winter temperatures of -8˚C.
Mulch is applied around the bushes to encourage healthy growth, and in the spring they are fed with a controlled-release fertiliser. The soil they are grown in has a low pH, which suits tea as it requires acid soil. The bushes are watered during long dry spells.
The plants are slow-growing and produce white flowers in the autumn.
This species at Kew
Tea bushes can be seen growing in the Woodland Glade near the Rhizotron and Xstrata Treetop Walkway.
There are over 60 specimens of Camellia sinensis in Kew's Economic Botany Collection. These are available to researchers by appointment.
Dried specimens of C. sinensis are held in Kew’s Herbarium. Details of a specimen collected in Mozambique in 2007 can be viewed online in Kew's Herbarium Catalogue.
View specimens of Camellia sinensis online