Camellia sinensis in the context of "Twig"

Camellia (pronounced /kə.ˈmɛ.li.ə/ or /kə.ˈmiː.li.ə/) is a genus of flowering plants in the family Theaceae. They are found in tropical and subtropical areas in eastern and southern Asia, from the Himalayas east to Japan and Indonesia. There are more than 220 described species; almost all are found in southern China and Indochina. Camellias are popular ornamental, tea, and woody-oil plants cultivated worldwide for centuries. Over 26,000 cultivars, with more than 51,000 cultivar names, including synonyms, have been registered or published.

The leaves of C. sinensis are processed to create tea, and so are of particular economic importance in East Asia, Southeast Asia, and the Indian subcontinent, with the processed leaves widely sold and consumed globally. The ornamental C. japonica, C. sasanqua and their hybrids are the source of hundreds of garden cultivars. C. oleifera produces tea seed oil, used in cooking and cosmetics.

Tea is an aromatic beverage prepared by pouring hot or boiling water over cured or fresh leaves of Camellia sinensis, an evergreen shrub native to East Asia which originated in the borderlands of south-western China, north-east India and northern Myanmar. Tea is also made, but rarely, from the leaves of Camellia taliensis and Camellia formosensis. After plain water, tea is the most widely consumed drink in the world. There are many types of tea; some have a cooling, slightly bitter, and astringent flavour, while others have profiles that include sweet, nutty, floral, or grassy notes. Tea has a stimulating effect in humans, primarily due to its caffeine content.

An early credible record of tea drinking dates to the third century AD, in a medical text written by Chinese physician Hua Tuo. It was popularised as a recreational drink during the Chinese Tang dynasty, and tea drinking spread to other East Asian countries. Portuguese priests and merchants introduced it to Europe during the 16th century. During the 17th century, drinking tea became fashionable among the British, who later started to plant tea on a large scale in India, where it had previously been used only as a medicine.

Asterids are a large clade (monophyletic group) of flowering plants, composed of 17 orders and more than 80,000 species, about a third of the total flowering plant species. The asterids are divided into the unranked clades lamiids (8 orders) and campanulids (7 orders), and the single orders Cornales and Ericales. Well-known asterids include dogwoods and hydrangeas (order Cornales), tea, blueberries, cranberries, kiwifruit, Brazil nuts, argan, sapote, and azaleas (order Ericales), sunflowers, lettuce, common daisy, yacon, carrots, celery, parsley, parsnips, ginseng, ivies, holly, honeysuckle, elder, and valerian (clade campanulids), borage, forget-me-nots, comfrey, coffee, frangipani, gentian, pong-pong, oleander, periwinkle, basil, mint, rosemary, sage, oregano, thyme, lavender, wild dagga, olives, ash, teak, foxgloves, lilac, jasmine, snapdragons, African violets, butterfly bushes, sesame, psyllium, potatoes, eggplants, tomatoes, chilli peppers, tobacco, petunias, morning glory, and sweet potato (clade lamiids).

Most of the taxa belonging to this clade had been referred to as Asteridae in the Cronquist system (1981) and as Sympetalae in earlier systems. The name asterids (not necessarily capitalised) resembles the earlier botanical name but is intended to be the name of a clade rather than a formal ranked name, in the sense of the ICBN.

Herbal teas or herb teas, technically known as herbal infusions, and less commonly called tisanes, are beverages made from the infusion or decoction of any herbs, spices, or other plant material in water that is not derived from the tea plant (Camellia sinensis). Many herbs used in teas/tisanes are also used in herbal medicine and in folk medicine. Herbal teas are not technically teas because they are not brewed from the tea plant.

The term "herbal tea" is often used to distinguish these infusions from true teas (e.g., black, green, white, yellow, oolong), which are prepared from the tea plant (Camellia sinensis) or, more rarely, its close relatives (such as Camellia taliensis). Beverages actually created from tea and combined with material from other plants are known as "blended teas", "scented teas", or "flavored teas". Examples include jasmine tea, genmaicha, and Earl Grey tea. Unlike true teas, most tisanes do not naturally contain caffeine (though tea can be decaffeinated, i.e., processed to remove caffeine).

Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class and is the most commonly consumed psychoactive substance globally. It is mainly used for its eugeroic (wakefulness promoting), ergogenic (physical performance-enhancing), or nootropic (cognitive-enhancing) properties; it is also used recreationally or in social settings. Caffeine acts by blocking the binding of adenosine at a number of adenosine receptor types, inhibiting the centrally depressant effects of adenosine and enhancing the release of acetylcholine. Caffeine has a three-dimensional structure similar to that of adenosine, which allows it to bind and block its receptors. Caffeine also increases cyclic AMP levels through nonselective inhibition of phosphodiesterase, increases calcium release from intracellular stores, and antagonizes GABA receptors, although these mechanisms typically occur at concentrations beyond usual human consumption.

Caffeine is a bitter, white crystalline purine, a methylxanthine alkaloid, and is chemically related to the adenine and guanine bases of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). It is found in the seeds, fruits, nuts, or leaves of a number of plants native to Africa, East Asia, and South America and helps to protect them against herbivores and from competition by preventing the germination of nearby seeds, as well as encouraging consumption by select animals such as honey bees. The most common sources of caffeine for human consumption are the tea leaves of the Camellia sinensis plant and the coffee bean, the seed of the Coffea plant. Some people drink beverages containing caffeine to relieve or prevent drowsiness and to improve cognitive performance. To make these drinks, caffeine is extracted by steeping the plant product in water, a process called infusion. Caffeine-containing drinks, such as tea, coffee, and cola, are consumed globally in high volumes. In 2020, almost 10 million tonnes of coffee beans were consumed globally. Caffeine is the world's most widely consumed psychoactive drug. Unlike most other psychoactive substances, caffeine remains largely unregulated and legal in nearly all parts of the world. Caffeine is also an outlier as its use is seen as socially acceptable in most cultures and is encouraged in some.

Assam tea is a black tea named after Assam, India, the region of its production. It is manufactured specifically from the plant Camellia sinensis var. assamica (Masters). Assam's people tried to plant the Chinese varieties in Assam soil but did not succeed. Assam tea is now mostly grown at or near sea level and is known for its body, briskness, malty flavour, and strong, bright colour. Assam teas, or blends containing Assam tea, are often sold as "breakfast" teas. For instance, Irish breakfast tea, a maltier and stronger breakfast tea, consists of small-sized Assam tea leaves.

The state of Assam is the world's largest tea-growing region by production, lying on either side of the Brahmaputra River, and bordering Bhutan, Bangladesh, Myanmar and very close to China. This part of India experiences high rainfall; during the monsoon period, as much as 250 to 300 mm (10 to 12 in) of rain falls per day. The daytime temperature rises to about 36 °C (96.8 °F), creating greenhouse-like conditions of extreme humidity and heat. This tropical climate contributes to Assam tea's unique malty taste, a feature for which this tea is well known.

The Ericales are a large and diverse order of flowering plants in the asterid group of the eudicots. Well-known and economically important members of this order include tea and ornamental camellias, persimmon, ebony, blueberry, cranberry, lingonberry, huckleberry, kiwifruit, Brazil nut, argan, sapote, azaleas and rhododendrons, heather, heath, impatiens, phlox, Jacob's ladder, primroses, cyclamens, shea, sapodilla, pouterias, and trumpet pitchers.

The order includes 22 families, according to the APG IV system of classification.