Camellia sinensis

• 1. Introduction

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  Camellia sinensis, the tea plant, grows on the island of Shapinsay in the Orkney Islands, at 59 degrees north. That is the northernmost tea plantation on record, and the same species is also grown commercially at the equator. This evergreen shrub or small tree belongs to the flowering plant family Theaceae. Its leaves, leaf buds and stems become tea. Yet the plant carries a name that people also hang on unrelated Australian and New Zealand shrubs. It has also been renamed and reshuffled by botanists many times. How can a single species produce such different drinks? Who gave it the name it carries today? Where did the first tea plants come from, when no wild population is known? And why does a plant that feeds so many people also carry a built-in insecticide?

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• 2. One Shrub, Six Teas

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  Black tea sits at one end of the oxidation scale and white tea sits at the other. Between them lie yellow tea, green tea, oolong and the dark teas, a group that includes pu-erh. All of these come from just two of the plant's five varieties, C. sinensis var. sinensis and C. s. var. assamica. The difference lies in processing, not in the species. Makers allow the leaves to oxidize to different degrees, and that single choice sets the final drink apart. Black tea is the most oxidized and white tea the least. One tea breaks the leaf rule entirely. Kukicha, known as twig tea, is made from the twigs and stems of the same plant instead of the leaves.

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• 3. A Name Built From Two Places

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  The word sinensis is Botanical Latin for "from China". It joins sin, the Latin root for China, to the suffix -ensis, which marks a place of origin. The genus name Camellia honors a man who probably never saw a tea field. Georg Kamel lived from 1661 to 1706 and was born in Moravia. He served as a Jesuit lay brother and pharmacist, and he worked as a missionary in the Philippines. His name was Latinized to give the genus its title. The plant was not always filed under it. Linnaeus placed tea in a separate genus called Thea. In 1818, Robert Sweet merged Thea into Camellia and moved every former Thea species across. The common name tea tree has been in use since 1760, but the label was later applied to Australian and New Zealand shrubs of the myrtle family. The first such use dates to 1790. Those shrubs, mostly in the genera Leptospermum or Melaleuca, are unrelated to tea. The botanical trail left behind is long, since the species accumulated synonyms covering 45 species names alone.

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• 4. Anatomy of a Tea Bush

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  Left alone, a tea plant can climb as high as 20 m. Commercial growers rarely allow it. They trim plantation bushes to a flat top at about 1 m, which also keeps the leaves within reach of pickers. The bark on the trunk is smooth and gray with a yellow or brown tone. Young branches are yellow with a gray cast, and new twigs are red-purple with white hairs. In older trees the trunk can reach 40 cm across. Below ground, a seedling relies on one dominant taproot. A mature bush adapts to its soil. Shallow soils or high water tables produce a fibrous, shallow root system, while deep soils have yielded roots found at 5.5 m. The leaves are leathery, shining dark green above and pale green below. They are smaller on cultivated plants than on wild ones. Each has a raised central vein, with seven to nine smaller veins branching off on each side. The edges carry forward-pointing teeth, from coarse to very fine. The white flowers have six to eight petals and sit in the leaf joints, alone or in clusters of up to three. Five sepals measuring 3-5 mm sit at the back. Inside, numerous hairless stamens 8-13 mm long are arranged in as many as five concentric whorls. The fruit is a globe-shaped capsule, 1-1.5 cm tall and 1.5-3.5 cm wide, holding one or two brown to almost black seeds in each of its chambers. Pressed, those seeds and the seeds of the oil-seed camellia, Camellia oleifera, give tea oil, a sweetish cooking oil. It should not be confused with the medicinal essential oil called tea tree oil. A well-tended bush reaches peak output at 30 to 50 years of age.

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• 5. Five Varieties

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  In 2017, Chinese scientists sequenced the genome of C. s. var. assamica and found about three billion base pairs. That was larger than most plants sequenced up to then. The species is formally split into five accepted varieties. Var. sinensis is told apart by a style fused at the tip into three lobes. It grows across a wide belt of China, from Fujian and Zhejiang to Sichuan and Yunnan, and in Taiwan. Var. assamica has leaves that are villous along the midvein underneath. It extends from Yunnan, Guangdong, Guangxi and Hainan in China through Bhutan, Laos, Myanmar, Nepal, Thailand and Vietnam. Both are widely grown for tea. The other three are narrower in range. Var. pubilimba has white, pubescent sepals and occurs in parts of Guangdong, Guangxi, Hainan and Yunnan. Var. dehungensis has leaf undersides covered in pressed-down hairs and is found in southern Yunnan. Var. madoensis has a style that is free halfway to the base and is recorded from Phu Yen in Vietnam. Another form was long treated as a separate species. SY Hu named it C. waldenae, but it was later identified as a variety of C. sinensis. It grows on Sunset Peak and Tai Mo Shan in Hong Kong and also occurs in Guangxi.

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• 6. Tracing the Origins

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  No wild population of Chinese small leaf tea is known, so its birthplace remains a matter of speculation. The best guess is southern China, perhaps after crossing with unknown wild relatives. Experts disagree on the wider homeland. One theory points to the borderlands of far eastern India, northern Myanmar and southwestern China. Others favor Yunnan province in the northeast of that region. A plant database lists a far broader native range, taking in Assam, the eastern Himalayas, Laos, Thailand and Vietnam. Genetics adds another layer. Chinese Assam tea appears to have two separate parentages. One lineage lives in southern Yunnan, around Xishuangbanna and Pu'er City. The other is in western Yunnan, near Lincang and Baoshan. Many southern Yunnan types have crossed with a close relative, Camellia taliensis. Western Yunnan Assam tea resembles Indian Assam tea, so both may descend from one parent plant. Yet Indian Assam tea shares no haplotypes with the western Yunnan type, which suggests it was domesticated independently. Some Indian Assam tea also shows signs of crossing with Camellia pubicosta. Assuming a generation of 12 years, small leaf tea diverged from Assam tea around 22,000 years ago, matching the last glacial maximum. Chinese Assam and Indian Assam diverged about 2,800 years ago. The Cambodia type was once classed as an Assam tea, but later genetic work showed it is a hybrid of Chinese small leaf tea and Assam tea.

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• 7. Terroir From Assam to Japan

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  In 1836, the British brought Chinese small leaf tea into India. The following year, in 1837, the first tea estate in India was established in Assam. Assam tea comes from the near sea-level, heavily forested northeast, and it is rich and full-bodied. Its makers use either the orthodox process or the "crush, tear, curl" method, known as CTC. Darjeeling is a different story. Its tea comes from var. sinensis in the cool, wet foothills of the Himalayas. It is delicately flavored and counted among the finest teas in the world. Darjeeling plantations give three distinct harvests, called flushes. The first, in spring, is light and aromatic. The second, in summer, has a little more bite. The third, in autumn, is judged lesser in quality. Some Darjeeling plants appear to be hybrids of Chinese small leaf tea, native Indian Assam, and possibly wild relatives. The Nilgiri region in the south sits almost as high. Its teas are subtle and gentle and are often blended with stronger ones. The Chinese plant itself is a multi-stemmed, small-leafed bush reaching about 3 m, and its tea use dates back some 3,000 years. Japan has grown tea since as far back as the 9th century. Its cultivars include Benifuuki, Fushun, Kanayamidori, Meiryoku, Saemidori, Okumidori and Yabukita.

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• 8. Caffeine and Claims

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  The caterpillars of the willow beauty moth, Peribatodes rhomboidaria, will eat tea leaves. Other creatures fare worse. Fresh leaves hold about 4% caffeine along with related compounds such as theobromine. The caffeine works as a natural pesticide and can paralyze and kill the insects feeding on the plant. The leaves make it chiefly while young. Researchers harvested young leaves and used reverse transcription PCR to study the genes behind the process. The gene TCS1 encodes caffeine synthase, and young leaves carry high concentrations of its transcripts. The chemistry then runs in steps. Xanthosine becomes 7-methylxanthosine, then 7-methylxanthine, then theobromine, and finally caffeine. The route resembles the one in coffee and guayusa. People have also drunk green tea for health for thousands of years. Scientific studies show mixed results, with modest effects in certain groups. The United States Food and Drug Administration has approved one green tea extract ointment for genital warts. A medical database rates black tea as likely effective for mental alertness. It rates the tea as possibly ineffective against various cancers and diabetes.

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