Tea

• 1. Introduction

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  Tea is a shrub's leaves steeped in hot water, and by the third century AD a Chinese physician named Hua Tuo was already writing about it as a mental tonic, claiming that "to drink bitter t'u constantly makes one think better." Today tea trails only plain water as the world's most consumed drink. It comes from Camellia sinensis, an evergreen shrub native to the borderlands of south-western China, north-east India and northern Myanmar. Some brews taste cooling, bitter and astringent, others carry sweet, nutty, floral or grassy notes, and nearly every cup delivers a dose of caffeine.

  How did a leaf once chewed raw or fermented for a snack turn into a drink brewed, iced, buttered and salted across the world? Left untamed, the tea plant can grow into a tree as tall as 16 metres, a shape few tea drinkers ever picture when they lift a cup.

• 2. Origins In China

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  In Yunnan, early use of the plant was medicinal, prized as a treatment long before anyone drank it purely for pleasure. Further north in Sichuan, people began boiling tea leaves into a concentrated liquid without adding other herbs, turning tea into what one account calls "a bitter yet stimulating drink, rather than a medicinal concoction." Chinese legend credits the mythical ruler Shennong with discovering tea in 2737 BC, though evidence points instead to an introduction from south-west China.

  The word tu appears in the ancient Shijing to describe a kind of "bitter vegetable," a term that may have covered several plants, including sow thistle, chicory and smartweed, as well as tea. The Chronicles of Huayang record that the Ba people of Sichuan presented tu to the Zhou king. After the Qin dynasty conquered Ba and its neighbour Shu, the 17th-century scholar Gu Yanwu wrote in Ri Zhi Lu that "it was after the Qin had taken Shu that they learned how to drink tea." A Qin dynasty general, Liu Kun, even wrote a letter requesting that some "real tea" be sent to him.

  In 2016, archaeologists uncovered the earliest known physical evidence of tea inside the mausoleum of Emperor Jing of Han in Xi'an, showing that Han dynasty emperors drank it as early as the second century BC. A Han-era work called The Contract for a Youth, written by Wang Bao in 59 BC, gives the first known reference to boiling tea, instructing a servant that "he shall boil tea and fill the utensils" and "he shall buy tea at Wuyang." The same period produced the first record of tea cultivation, on Meng Mountain near Chengdu.

  Before the Tang dynasty, tea drinking remained a mostly southern Chinese custom centred on Jiankang, and northern aristocrats reportedly dismissed it as inferior to yogurt. That changed once the Tang dynasty took hold, when the drink spread outward to Korea, Japan and Vietnam. The 8th-century writer Lu Yu set the trend down in ink with The Classic of Tea, and the modern Chinese character for tea, cha, appeared in his text once he dropped a single stroke from the older word tu.

• 3. Botanical Roots

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  The probable birthplace of the tea plant lies near the source of the Irrawaddy River, in a fan-shaped zone reaching into south-east China, Indo-China and Assam. That natural range runs from Nagaland, Manipur and Mizoram along the Burma frontier in the west, across China as far as Zhejiang Province in the east, and south through the hills into Burma, Thailand and Vietnam. The west-east axis stretches roughly 2,400 km, between longitude 95 and 120 degrees east, while the north-south axis covers about 1,920 km, running from northern Burma at latitude 29 degrees north down through Yunnan, Tongkin, Thailand and Laos to Annan at latitude 11 degrees north.

  Chinese small-leaf tea, Camellia sinensis var. sinensis, may have arisen in southern China through hybridisation with unknown wild tea relatives, though no wild populations survive to confirm it. Assam-type tea, C. sinensis var. assamica, appears to have two separate parent lines, one in southern Yunnan around Xishuangbanna and Pu'er City, the other in western Yunnan around Lincang and Baoshan. Many southern Yunnan Assam plants have hybridised with a related species, Camellia taliensis, while the western Yunnan line shares genetic ground with Indian Assam-type tea, suggesting both trace back to a shared parent plant where south-western China, Indo-Burma and Tibet meet.

  Two principal varieties dominate cultivation: C. sinensis var. sinensis, used for most Chinese, Formosan and Japanese teas, and C. sinensis var. assamica, used in pu-erh and most Indian teas apart from Darjeeling. Leaf size sorts the plants into three classes: Assam type, with the largest leaves; China type, with the smallest; and Cambodian type, of intermediate size, later shown by genetic work to be a hybrid of the other two. Grown at elevations of up to 2000 metres, tea plants develop more slowly but yield a better flavour, and a healthy bush sends out a new flush of harvestable leaves every 7 to 15 days.

  Indian Assam tea, however, shares no haplotypes with its western Yunnan relative, pointing to an independent domestication rather than a shared origin. Some Indian Assam tea also appears to have hybridised with the species Camellia pubicosta. Assuming a generation length of 12 years, geneticists estimate that Chinese small-leaf tea split from Assam tea around 22,000 years ago, while Chinese Assam tea and Indian Assam tea diverged only about 2,800 years ago, a split that lines up with the last glacial maximum.

• 4. Words For Tea

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  Three Chinese-rooted sounds, te, cha and chai, underlie nearly every language's name for the drink. Cha was the first to enter English, arriving in the 1590s by way of Portuguese traders who picked up the Cantonese pronunciation while trading in Macao. The more familiar tea form followed in the 17th century, brought by the Dutch, who took it either indirectly from the Malay teh or directly from the te pronunciation used in Min Chinese.

  Chai, meaning "spiced tea," began as a northern Chinese pronunciation of cha that travelled overland into Central Asia and Persia, picking up a Persian ending, yi, along the way. Even the Chinese word itself may trace back further still, possibly to an archaic Austro-Asiatic root, la, meaning "leaf," from the non-Sinitic languages spoken in the plant's original home in south-western China or Burma.

• 5. Tea Reaches Europe And Russia

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  In 1545, the Venetian writer Giambattista Ramusio gave Europe its first known reference to the drink, in his Delle navigationi e viaggi, spelling it chiai. Western priests and merchants in China had already begun calling it cha throughout the 16th century. The first recorded shipment by a European nation came in 1607, when the Dutch East India Company carried a cargo of tea from Macao to Java. Two years later, the Dutch bought their first consignment from Hirado in Japan for shipment to Europe.

  Tea became fashionable in The Hague, and from the Netherlands the Dutch carried the habit into Germany, France and across the Atlantic to New Amsterdam, later renamed New York. Russians met tea in 1567, when the Cossack leaders Petrov and Yalyshev visited China. In 1638, a Mongolian khan gave Tsar Michael I four poods of tea, roughly 65 to 70 kilograms.

  According to the historian Jeremiah Curtin, it was possibly in 1636 that Vassili Starkov was sent as an envoy to the Altyn Khan and was given 250 pounds of tea as a gift for the tsar. Starkov reportedly balked at first, seeing no use for a load of dead leaves, but the khan insisted, and tea entered Russian life. By 1679, Russia had signed a treaty securing regular tea shipments from China by camel caravan in exchange for furs, and the drink is now considered the country's de facto national beverage.

• 6. Britain's Tea Trade

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  In 1615, an East India Company officer named Richard Wickham wrote home from Japan asking a Macao merchant for 'the best sort of chaw,' the first known mention of tea in English. In 1637, the traveller Peter Mundy encountered it in Fujian and described it as 'chaa, only water with a kind of herb boyled in it.' Tea went on sale in a London coffee house in 1657, Samuel Pepys tasted it in 1660, and Catherine of Braganza brought the habit into the English court when she married Charles II in 1662.

  Even so, tea stayed a rare and costly import in Britain until the 18th century. English drinkers took to stirring sugar and milk into black tea, which overtook green tea in popularity during the 1720s. Widespread smuggling through the century let ordinary people afford tea long before it was cheap to buy legally, and the British government finally scrapped the tax on tea by 1785, killing off the smuggling trade in the process.

  At first, tea in Britain and Ireland was a luxury reserved for special occasions such as religious festivals, wakes and communal work gatherings. Prices fell steadily through the 19th century, especially once Indian tea arrived in bulk, and by the century's end tea had become an everyday drink at every level of society. Its popularity even shaped politics: the Tea Act of 1773 provoked the Boston Tea Party, which escalated into the American Revolution.

  Britain's growing tea habit also created a trade deficit that helped trigger the Opium Wars. In 1685, the Qing Kangxi Emperor decreed that all goods bought from China had to be paid for in silver coin or bullion. Foreign traders turned to opium as a product they could sell into China to recoup that silver, and when the Chinese government tried to curb the opium trade, war followed.

• 7. Tea Growing In India

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  British planters introduced Chinese small-leaf tea to India in 1836, hoping to break China's grip on the trade. In 1841, Archibald Campbell carried Chinese tea seeds from the Kumaun region and began experimenting with planting in Darjeeling. The Alubari tea garden opened in 1856, and Darjeeling tea production began in earnest.

  In 1848, the East India Company sent Robert Fortune to China to bring the tea plant back to Britain, a mission he began in secrecy during the lull between the First and Second Opium Wars. Most of the Chinese plants he brought back to the Himalayas failed to survive. The British instead found a different tea variety already growing wild in Assam and northeast India, and crossed it with the Chinese small-leaf plant.

  Using techniques borrowed from Chinese growers, the British colonial government built up the industry by offering land in Assam to any European willing to cultivate it for export. Tea was originally drunk only by Anglo-Indians, and it did not become popular across India until the 1950s, following a successful advertising campaign by the India Tea Board. The British also planted the tea industry in Sri Lanka, then called Ceylon, in 1867.

• 8. Chemistry, Trade And Modern Challenges

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  Caffeine makes up roughly 3% of tea's dry weight, translating into 30 to 90 milligrams in a 250 mL cup depending on the type, brand and brewing method. One study found that a gram of black tea yields 22 to 28 milligrams of caffeine, compared with just 11 to 20 milligrams from a gram of green tea. Tea also carries small amounts of theobromine and theophylline, xanthine stimulants related to caffeine.

  Polyphenols, including flavonoids, epigallocatechin gallate and other catechins, make up 30 to 40% of the leaves, giving tea its astringency. Despite decades of preliminary research into whether green or black tea might guard against disease, there is no solid evidence that these compounds affect human health. Tea's main nutritional contribution is the mineral manganese, at 0.5 milligrams per cup, or 26% of the Reference Daily Intake; fluoride can also build up in older "brick tea" leaves at levels high enough to pose a risk if drunk to excess.

  China, India, Kenya and Sri Lanka together grow 81% of the world's tea, and global production reached 29.8 million tonnes in 2022, with China supplying 49% and India 20% of the total; Kenya, Sri Lanka and Turkey trail as secondary producers. The industry also has a fraud problem: cheaper ingredients are sometimes substituted for tea, or leaves are adulterated with undeclared colours and flavours, with origin, picking season and processing technique all vulnerable to misrepresentation.

  Tea production in Kenya, Malawi, Rwanda, Tanzania and Uganda still uses child labour, according to the U.S. Department of Labor's List of Goods Produced by Child Labor or Forced Labor, and pickers on plantations in developing countries often face harsh conditions for less than a living wage. Climate change now threatens the crop directly, shortening growing seasons and exposing fields in China and India to heatwaves, and growers are turning to agroforestry, soil-enriching legumes and new heat-tolerant varieties to keep their harvests alive.