Tea

Camellia sinensis L . Kuntze

Family: Theaceae

Introduction

• Tea (Camellia sinensis), is likely the most widely used non-alcoholic beverages around the world, or certainly a close second to coffee. Cultivation of tea goes back at least to 2000 B.C. in eastern Asia, where brews of tea were used for medicinal purposes.

• Its documented use as a social drink dates from the 5th century in China. Therefore, tea was brought into cultivation in Southeast Asia, most probably in the region of southeastern China, former Indochina, or Assam in India.

An evergreen shrub to small tree that can only be grown where frost is totally absent and where the temperature never gets very high. This means that tea is best grown on tropical hills in China, India, Sri Lanka and Malaysia, where the annual rainfall is abundant. More than half of the world production comes from China, often from small plots, but tea is being grown around the world wherever the climate is right.

The tea plant is in the polymorphic species Camellia sinensis Kuntz, but recent findings show that this plant of commerce is derived from more than one species.

• Two distinct varieties of tea-plant are generally recognised, the small-leaved China (sinensis) and the large-leaved Assam (assamica) which have been raised to a specific rank by a well-known tea botanist.

Careful field observations, however, reveal that more than one or two species are involved in the evolution of the present-day tea-plant of commerce.

Considerable inter-specific hybridization has taken place in nature. Thus, the taxonomy of the tea-complex is confounded.

Botanical Description

Small evergreen tree to 16 m tall, usually pruned back to shrubs in cultivation, with strong taproot giving rise to a surface mat of feeder roots with endotrophic mycorrhizae;

Leaves

leaves alternate, lanceolate to obovate, up to 30 (usually 4 -15) cm long, 2-5 (7-12) cm broad, pubescent, sometimes becoming glabrous, serrate, acute or acuminate;

Flowers

flowers are 1-3 in number, in axillary or subterminal cymes, 2-5 cm broad, aromatic, white or pinkish, sepals and petals 5-7, pedicels 5-15 mm long; stamens numerous; ovary 3-5 carpellate, each carpel 4-6 ovulate;

Capsules/Seeds

capsules depressed - globose, brownish, lobate, to 2 cm broad, with 1-3 sub-globose seeds in each lobe; approximately 500 seeds per kg.

Cultivation

An evergreen plant and grows in tropical to sub-tropical climates. In addition to tropical climates with a good amount of rain, it also prefers acidic soils. Many high quality tea plants grow at elevations up to 1500 meters , as the plants grow more slowly and acquire a better flavor. Only the top 50 mm of the mature plant are picked. These buds and leaves are called flushes, and a plant will grow a new flush every seven to ten days during the growing season.

• Tea plants will grow into a tree if left undisturbed, but cultivated plants are pruned to waist height for ease of plucking.

• Two principal varieties are used: the small-leaved China plant (C. sinensis var sinensis) and the large-leaved Assam plant (C. sinensis var assamica).

The tea-plant, in the natural state, grows into a small or medium-sized tree, but in commercial plantations it is pruned and trained to form a many-branched low bush and is encouraged to produce vigorous vegetative growth by adopting an appropriate schedule of fertilizer applications

Geographical Distribution

• The important tree growing countries are India, Sri Lanka and East Africa;

• Japan and Indonesia also produce sizeable quantities of tea.

• It is also grown in Bangladesh, China, Georgia, Argentina and some other countries.

• Native to Southeast Asia, found from Sri Lanka and India to Assam and China, tea has been planted widely in tropical and subtropical areas.

• Near the Equator, it ranges up to nearly 2,000 m elevation.

Tea Map of the World

Ecology

• Ranging from Warm Temperate Dry to Wet through Tropical Very Dry to Moist Forest Life Zones,

Reported to tolerate annual precipitation of 700 to 3100 mm, annual temperature of 14 to 27°C, and pH of 4.5 to 7.3.

• Although evergreen, tea is intolerant of frost, and requires equable, humid, warm situations; some Chinese tea varieties can tolerate cooler climes.

Thrives on tropical red earths and deep, well-drained, acid (pH 4.5-6.0) soils. Mean minimum temperatures should not fall below 13°C, nor maximum go above 30°C. An annual rainfall of 120 cm or more is desirable. Several months with less than 5 cm rainfall each are intolerable

Climate

Tea is grown on plantation scale in many areas of the world in warm and moist climate. These range from Georgia (USSR) to Corrientes (Argentina). It is grown from sea level to about 2460 m. A well distributed rainfall is essential for its cultivation. The rainfall varies from 125 cm to 750 cm in the tea-growing regions in this country.

Soil

Tea is planted on soils of widely different geological origin and of almost all physical types. A well drained, deep and friable loam or forest land rich in organic matter is ideal.

Tea soils are acidic (pH 4 to 6), low in calcium and generally rich in iron and manganese.

Cultivation/Propagation

Tea is propagated from seed, but high yielding clonal material has also become popular. The plants are initially raised in nurseries to produce healthy plants.

Twelve to 18 months-old nursery seedlings are used for planting in the field.

The vegetative propagation of selected tea plant cuttings, each with a leaf and an internode has been standardized

Tea is propagated either from seeds or by vegetative means. Seed-bearing trees, selected for yield and quality, are cross-fertilized, and the progeny of seed sown in new seed orchards, spaced 300 - 350 trees/ha.

- Under better conditions, selected clones are propagated vegetatively. It requires 4-12 years to bear seed. Better seeds from seed orchards are planted in nursery or at stake, protected from sun and wind. At first, seedlings should be shaded.

- Seedlings 6-12 months old may be out-planted with a ball of earth, while much older seedlings can be planted bare-rooted, cutting the stem 10 cm from the ground mark.

Normally preferred is single-internode cuttings, cut just above a node with an axillary bud.

The cuttings inserted in the soil at an angle so that the subtending leaf rests on the medium.

Hedge plantings in rows about 1.5 m apart spaced 60 cm apart in the row give better initial yields and may facilitate mechanical harvesting.

(Inter-plantings with shade trees is no longer recommended).

In Assam, India the 'bushes' are allowed to grow for 3 years and pruned across the leaders and laterals at about 45 cm. Subsequently they are top-pruned each year; or the entire plant is trimmed back to 15 cm when bush is 1- 1.5 m tall

• The area intended for planting is first cleared of forest growth and adequate steps are taken to prevent soil erosion.

• Planting lines are traced (as at present on contour on hill slopes) and pits of a convenient size (generally 30 - 45 cm deep and 24 cm wide) are dug.

• The normal accepted spacing is 120 X 75 cm, accommodating about 10,000 plants in a hectare. The soil is heavily mulched during the initial one or two years.

• The plant is left for 4 years before any leaves can be plucked. Constant pruning and shaping will form its required height of 1.20m, hence creating the plucking table and giving a good framework to the bush.

• It will not reach full growth until the fifth year when it will begin to produce. It will still be pruned at varying intervals - on average every two years - in order to keep it at a good height for plucking.

Cultural practices

A system of shading the tea plants is practiced in some countries (but not nowadays). For example, in southern India, the silver oak (Grevilla robusta) is the preferred choice. Other trees used for shading are Erythrina lithosperma (dadap), Acacia and Albizia. Albizia species are used in tea gardens in northern India.

Weeds compete with the tea plant for nutrients, and weed control is important in tea plantations. In recent years , the control of weeds with chemicals has gained popularity. Grasses and broad-leaf dicot weeds are kept under check. Pests and diseases are effectively controlled with chemicals.

Fertilization

A fertilizing scheme is followed from the nursery stage up to maturity:- a special 1:1:1 NPK soluble fertilizer mixture is used in the nursery; - a 4:3:3 NPK mixture in the first 3 years in the clearing (kawasan baru), and - thereafter the dosage of the fertilizer applied is varied, depending on the type of tea, its performance, soil fertility and the yield potential of the crop. On an average 10 kg of nitrogen is applied for every 100 kg of the crop.

Tea readily responds to the application of nitrogen (N) and potassium (K). K is applied at the rate of 40 to 50 percent of the amount of N applied, depending on the soil type and weather conditions.

Zinc deficiency can be a limiting factor in tea production in some areas and a schedule of foliar application of zinc sulphate usually 11 kg per hectare in alternate years is recommended.

TRAINING, PRUNING AND PLUCKING

• The tea-plant is initially trained into a small bush by centering low within a few months of planting, by removing the central leader stem in order to encourage development of lateral branches.

• The lateral branches are cut to a convenient height of 40 to 50 cm and the growth above this is periodically cut.

• Thus a small, compact bush is formed. New shoots are allowed to grow unhampered and these shoots are tipped (petik), leaving a growth of 20 to 30 cm above the pruning cut, depending on that kind of plant. The crop is then harvested at regular intervals.

• The plant is left for 4 years before any leaves can be plucked. Constant pruning and shaping will form its required height of 1.20m, hence creating the plucking table and giving a good framework to the bush. It will not reach full growth until the fifth year when it will begin to produce. It will still be pruned at varying intervals - on average every two years - in order to keep it at a good height for plucking.

Harvesting• A mature tea plant does not usually live for

more than 40 or 50 years. Nonetheless some varieties can live up to 100 years.

• At the end of the fifth year, the tea plant is ready to be harvested. This operation, which consists of a light, repeated, pruning of the young shoots, is carried out in a 7 to 15 days cycle, depending on the growth, the climate and the amount of tea to be plucked.

• Terminal sprouts with 2- 3 leaves are usually hand-plucked, 10 kg of green shoots (moisture content of 75- 80%) produce about 2.5 kg dried tea.

• Leaves are harvested on the new growth. Generally a worker only plucks the terminal two leaves, because these have the best flavor. A person can harvest 40 to 80 pounds of leaves per day.

• Leaves that are slow in development always make a better flavored product.

Processing and classification

• Tea is a beverage made by steeping processed leaves, buds, or twigs of the tea bush, Camellia sinensis, in hot water for a few minutes.

• The processing can include oxidation, heating, drying, and the addition of other herbs, flowers, spices, and fruits.

• There are four basic types of true tea: black tea, oolong tea, green tea and white tea.

• The term "herbal tea" usually refers to infusions of fruit or of herbs (such as rosehip, chamomile, or jiaogulan) that contain no C. sinensis.

• (Alternative terms for herbal tea that avoid the word "tea" are tisane and herbal infusion.)

• These types of tea are distinguished by the processing they undergo. Leaves of Camellia sinensis soon begin to wilt and oxidize if not dried quickly after picking. The leaves turn progressively darker because chlorophyll breaks down and tannins are released.

• This process, enzymatic oxidation, is called fermentation in the tea industry although no true fermentation happens (that is, the process isn't microorganism-driven).

• The next step in processing is to stop the oxidation process at a predetermined stage by heating, which deactivates the enzymes responsible. In black tea this is done simultaneously with drying.

• Without careful moisture and temperature control during its manufacture and life thereafter, fungi will grow on tea. This form of fungus causes real fermentation that will contaminate the tea with toxic and sometimes carcinogenic substances and off-flavours, rendering the tea unfit.

• Tea is a natural source of the amino acid theanine, methylxanthines such as caffeine and theobromine, and polyphenolic antioxidant catechins.

• It has almost no carbohydrates, fat, or protein. It has a cooling, slightly bitter, and astringent flavor.

Tea is traditionally classified based on production

techniques

White TeaYoung leaves (new growth buds) that have undergone no oxidation; the buds may be shielded from sunlight to prevent formation of chlorophyll. White tea is produced in lesser quantities than most other styles, and can be correspondingly more expensive than tea from the same plant processed by other methods. It is less well known in countries outside of China, though this is changing with increased western interest in organic or premium teas.

Green Tea

The oxidation process is stopped after a minimal amount of oxidation by application of heat, either with steam, a traditional Japanese method, or by dry cooking in hot pans, the traditional Chinese method. Tea leaves may be left to dry as separate leaves or they may be rolled into small pellets to make gun-powder tea. This process is time consuming and is typically done with pekoes of higher quality. The tea is processed within one to two days of harvesting.

Oolong Oxidation is stopped somewhere between the standards for green tea and black tea. The oxidation process takes two to three days. In Chinese, semi-oxidized teas are collectively grouped as blue tea (青茶 , literally: blue-green tea), while the term "oolong" is used specifically as names for certain semi-oxidized teas.

Black Tea/Red Tea• The tea leaves are allowed to completely

oxidize. Black tea is the most common form of tea in southern Asia (Sri Lanka, India, Pakistan, Bangladesh, etc.) and in the last century many African countries including Kenya, Burundi, Rwanda, Malawi and Zimbabwe.

• The literal translation of the Chinese word is red tea, which is used by some tea lovers. The Chinese call it red tea because the actual tea liquid is red. Westerners call it black tea because the tea leaves used to brew it are usually black.

• However, red tea may also refer to rooibos, an increasingly popular South African tisane. The oxidation process will take between two weeks and one month.

• Black tea is further classified as either

orthodox or as CTC (Crush, Tear, Curl, a production method developed about 1932). Unblended black teas are also identified by the estate they come from, their year and the flush (first, second or autumn flush).

Flavours

• The quality of a tea depends on the cultivars used in a blend, the local climate for each, and the process technique. Flavor of tea comes from an essential oil called theol, and stimulation comes from the alkaloid theine (2-5%), which is essentially identical to caffeine.

• Tannins (quinones) give tea body, color, and pungency, and especially the tannin level controls how "dry" a tea can be. Great variability in tea flavor is created by blending teas from different regions.