tea plant

tea plant, (Camellia sinensis), evergreen flowering plant valued for its young leaves and leaf buds, from which the tea beverage is produced. Two principal varieties are used commercially, the small-leaved China plant (Camellia sinensis, variety sinensis) and the large-leaved Assam plant (C. sinensis, variety assamica). Hybrids of these two varieties are also grown. For information on the processing of tea and the history of its use, see tea.

The natural habitat of the tea plant is considered to be within the fan-shaped area between Nagaland, Manipur, and the Assam-Myanmar frontier in the west through to China, probably as far as Zhejiang province, in the east and from this line south through the hills of Myanmar and Thailand into Vietnam. The three main varieties of the tea plant—China, Assam, and Cambodia (C. sinensis, variety cambodiensis)—each occur in their most distinct form at the extremes of the fan-shaped area. Most of the world’s tea is cultivated within the plant’s native range, though significant production does occur in parts of Africa—namely, Kenya—and in South America.

Physical description and varieties

The cultivated tea plant is usually kept as a low mounded shrub and is pruned back frequently to encourage the development of young leaves. The fragrant white flowers have yellow centers and are about 4 cm (1.6 inches) wide. The mature leaves of the tea plant, differing in form according to variety, range from 3.8 to 25 cm (1.5 to 10 inches) in length, the smallest being those of the China variety. Tea leaves may be serrated, bullate (having a blistered appearance), or smooth and may be stiff or flabby. The leaf pose ranges from erect to pendant, and the degree of pubescence (leaf hairs) varies widely from plant to plant. In harvesting, or plucking, the shoot removed usually includes the bud and the two youngest leaves.

The China variety is a multistemmed bush that grows as high as 2.75 meters (9 feet). A hardy plant able to withstand cold winters, it has an economic life of at least 100 years. When grown at an altitude near that of Darjeeling, India (elevation 2,100 meters [7,000 feet]), and in Sri Lanka (Ceylon), it produces teas with valuable flavor during the season’s second flush, or growth of new shoots.

The Assam variety grows as a single-stem tree, ranging from 6 to 18 meters (20 to 60 feet) in height. The plant has an economic life of 40 years with regular pruning and plucking. There are five main subvarieties: the tender light-leaved Assam, the less tender dark-leaved Assam, the hardy Manipuri and Burma types, and the very large-leaved Lushai. The dark-leaved Assam plant, when its leaves are highly pubescent, produces very fine quality “golden tip” teas during its second flush. (The Chinese word pekho [pekoe], meaning “white hair” or “down,” refers to the “tip” in tea, which is correlated with quality.)

A third variety, the Cambodia variety, is not widely cultivated. It forms a single-stem tree growing to about 5 meters (16 feet) in height.

Cultivation

Scientific study of tea production began about 1890. Most tea-producing countries maintain scientific research stations to study every aspect of the subject, including seed production, clonal selection (for the propagation of single leaf cuttings), tea nursery management, transplanting, development of the bush and subsequent pruning and plucking, soil management and fertilizer use, and the ultimate replanting of the stand. Although procedures in all countries are related, appropriate details must be determined for each area. Since 1900, advancements in tea cultivation have dramatically increased the average yield per hectare. In the late 20th century, international demand for organic tea increased, prompting the return of many traditional tea farming methods supplemented with scientifically informed integrated pest management and soil management techniques.

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Three major considerations in planning a tea estate are climate, soil acidity, and labor availability.

A suitable climate has a minimum annual rainfall of 1,140 to 1,270 mm (45 to 50 inches), with proper distribution throughout the growing season. If there is a cool season, with average temperatures 11 °C (20 °F) or more below those of the warm season, the growth rate will decrease and a dormant period will follow, even when the cool season is the wetter one.

Soils must be acidic, as tea plants cannot be grown in alkaline soils. A desirable pH value is 5.8 to 5.4 or less.

A conventionally grown crop of 1,650 kg per hectare (3,640 pounds per acre) generally requires 3.7 to 4.9 workers per hectare (1.5 to 2 workers per acre) to pluck the tea shoots and perform other fieldwork. Hand plucking is often used for premium spring tea leaves and on steeply planted estates. Mechanical plucking is generally less selective and is frequently reserved for later harvests on the farms that can afford such mechanization and that have suitable terrain. Organically grown tea is more labor-intensive, though the harvest itself generally requires the same workforce as conventional fields.

Pests and diseases

The tea plant is subject to attack from at least 150 insect species and 380 fungal diseases, several of which can cause heavy crop losses. These problems are particularly acute in the plant’s native range. In northeastern India, for example, some 125 pests and 190 pathogenic fungi have been detected, and more than 100 pests and 40 plant diseases occur in the tea fields of Japan. Sri Lanka, where estates are close together or contiguous, has recorded many blights and suffered serious losses. African estates generally have little trouble with blights; the tea mosquito (Helopeltis theivora) is the only serious pest. The Caucasus, with a climate similar to that of Japan, grows the China variety of plant and has no serious pests or blights. Pests and diseases are typically controlled with pesticides. Some of these pesticides cannot be applied during the plucking season; others require that the two subsequent rounds of weekly pluckings be discarded.