Tea plant

The tea plant (Camellia sinensis) is a shrub or small tree, reaching 10–15 m in the wild but usually kept at 0.8–1.2 m in plantations for plucking. Leaves are evergreen and glossy with toothed margins, and the white five-petalled flowers have yellow stamens. All true teas — green, white, oolong, black and pu-erh — come from this one species and differ mainly in the degree of polyphenol oxidation. The plant favours a humid climate with acidic soil (pH 4.5–5.5), good drainage and frequent mist; higher-altitude gardens give finer leaf because of cooler temperatures and diffused light.

According to Plants of the World Online (Kew), the native range of tea is East Himalaya to South China and northern Indochina, including Hainan. Domesticated in China millennia ago, it is now grown throughout the tropics and subtropics: China and India lead production, followed by Kenya, Sri Lanka, Vietnam, Indonesia, Turkey and Japan. Tea is propagated mainly by cuttings and comes into picking about three years after planting.

Tea leaves contain catechins — led by epigallocatechin gallate (EGCG), usually 50–60% of total catechins — with total catechins at least 8% of the dried leaf according to the European Pharmacopoeia. They also contain 2–4% caffeine, the amino acid L-theanine (~1% of dry weight) that gives the umami finish, plus theobromine, flavonol glycosides and minerals. Green tea is unfermented, so its catechins remain intact, whereas black tea oxidises them into theaflavins and thearubigins.

Tea is the world's second most consumed beverage after water, taken as hot tea, iced tea, matcha and food flavouring; in Chinese, Japanese and East Asian traditional medicine it is used to promote alertness, aid digestion and cool the body. On clinical evidence, a meta-analysis of 55 randomised trials (Frontiers in Nutrition, 2023) found that green tea supplementation improved some cardiovascular risk factors such as total and LDL cholesterol; recent reviews (Molecules, 2025; Ferrari et al., 2025) note EGCG's potential in metabolism, antioxidant defence and cancer, though cancer-trial results remain mixed and inconclusive. EFSA assessed the safety of green tea catechins in 2018.

Tea drunk in moderation is generally safe; however, high-dose green tea extracts — especially EGCG taken on an empty stomach above about 800 mg/day — carry a risk of liver injury, and EFSA advises limiting supplemental doses. The caffeine in tea can cause insomnia and palpitations; pregnant women should limit intake. For conservation, Camellia sinensis is assessed by the IUCN as Data Deficient (DD; Rivers & Wheeler, e.T62037625A62037628, 2018) because the size and trend of the wild population are unknown; as a globally cultivated crop it is not threatened, and conservation priorities are landraces and heritage cultivars.