Plantation to Cup – How is Tea Grown

Tea is a perennial crop, except for a short period of dormancy which is restricted to some tea-growing areas, including parts of India, Argentina, China, Turkey and Iran, during which production is at a standstill. In the southern Indian tea growing area, bushes do not become dormant and plucking continues throughout the year. However, the crop harvested during different months varies and two distinct peaks are observed in the annual crop output curve. In the north Indian tea-growing regions, tea bushes remain dormant during the dry winter months and no tea is harvested during this time. The length of the dormancy period increases progressively with increasing distance from the equator.

Tea bushes are typically planted in single or double hedges, with a density ranging from 10,000 bushes to 15,000 bushes per hectare. These saplings take five to seven years to mature into yielding tea bushes and, if well-cultivated, yield tea leaves for as long as 100 to 150 years, with higher productivity in the first 50 years.

Tea production is influenced by weather conditions. Unusual patterns can decrease production or affect the quality and taste of the tea leaf. In 1997, Kenyan tea plantations suffered a sharp decrease in production due to damage caused by El Nino. In 1999, northeast Indian plantations endured the country’s worst drought in many decades, which caused a nationwide drop in production of 6% up to October 1999. However, favourable weather conditions in 1998 led to record crops in both India and Kenya.

Cultivation

In its wild state, tea grows best in regions that enjoy a warm, humid climate with a rainfall measuring at least 125 centimetres a year. Ideally, it likes deep, light, acidic and well-drained soil.

Given these conditions, tea will grow in areas from sea level up to altitudes as high as 2,500 metres above sea level. Tea varies in flavour and characteristics according to the type of soil, altitude and climate of the area in which it is grown. For example, Indian Darjeeling thrives in the chilly 2,000 metre-plus elevations of the Himalayan foothills. The cooler temperatures and thinner air contribute to leaves that produce superior bouquets and much richer flavours. The way tea is processed also affects the flavour and characteristics, as does the blending of different teas from different regions.

The wild tea plant can develop into a tree five to eight metres high. However, under cultivation, Camellia sinensis is kept to a height of approximately one metre for easy plucking. In Australia, plantations centre on two regions—north eastern New South Wales and the bigger tea-growing district on the Atherton Tableland in north Queensland.

Tea Estates

Tea is an example of a crop which is grown on special farms called estates or smallholdings. A smallholding is privately owned and can be as small as 0.5 hectares or can cover several hectares. In various tea-producing countries, where tea is grown on smallholdings, co-operatives are formed to build a tea-processing factory central to a group of small-holders. The owners of the smallholdings sell their plucked leaf to the factory for processing. 

Tea Picking and Harvesting

In most tea-producing countries, the labour-intensive method of picking, drying, crushing and fermenting tea has been used for centuries. The plucked leaves are collected in a basket or bag carried on the back of the plucker and when this is full it is taken to a collection point where the plucked leaf is weighed. It is then taken to the factory for processing, or "making", as tea manufacture is known in the tea trade.

In Australia, the industry has been forced to mechanise because tea production, especially tea plucking (harvesting), is extremely labour intensive. As a result, tea is harvested all year round with the use of mechanical harvesters. A harvester moves in between rows of tea bushes and operates like a giant lawn mower cutting off only tender new growth. A harvester can collect up to 1,500 kilograms of green tea leaves at a time at a rate of 4,000 kilograms an hour. On average, 1,000 kilograms of green leaf are required to make just over 200 kilograms of black tea.

The productivity of a tea plantation is measured by its yield of black tea per annum per hectare planted. A good yield is between 1,000 to 2,500 kilograms per hectare for hand picked plantations and 3,000 to 4,000 kilograms per hectare for mechanically harvested plantations.

At the Factory

On arrival at the factory, the plucked leaf is weighed and assessed for quality before being put in withering bins attached to huge air vents. The moisture in the leaf evaporates in the warm air leaving the leaves flaccid. This process can take between 10 to 16 hours, depending on the wetness of the leaf. Some factories will gently hasten the process with the aid of warm air fans.

The withered leaf is broken down by machine so that the natural juices, or enzymes, are released and on contact with the air will oxidise. The shredded leaves, called dhool, are then crushed and fed through the CTC (cut, tear and curl) or Rotovane machine. Its sharp teeth cut the leaf then tear it to release the juices that contain the tea flavour.

Orthodox. This is the traditional process of manufacturing tea. It begins with withering freshly picked tea leaves which lose approximately half their moisture within 12 to 18 hours. At the end of this process, the leaf is flaccid. The flaccid leaves then enter a process known as "rolling" which ruptures the leaf cells to release enzymes, and then twists or curls the leaf. Thereafter, to stop fermentation, the leaf is exposed to hot air by passing it through a chamber with perforated moving trays in a process known as "firing". This chamber is known as the drier. This dries the leaf and turns it a black colour. After the fired leaf is cooled, it is sorted by sieves.

CTC. This process is known as "CTC" because the tea leaf is crushed, torn and curled. The process is similar to orthodox tea-making. In CTC manufacture, after rolling, the tea leaves are passed through a machine, known as the CTC machine, where the leaves are cut or crushed to a greatly reduced size and most of their cells are ruptured. This intensifies the process of fermentation.  

Fermenting

The broken leaf is laid out either on trays or in troughs in a cool, humid atmosphere for up to two hours to ferment, or more correctly, oxidise. The trays are gently turned every so often throughout the period until all the leaves turn a golden russet colour and fermentation is complete. This remains one of the most challenging stages of production.

Drying

After fermentation, the leaf is dried or fired. This is done by passing the broken fermented leaf slowly through hot air chambers where all the moisture is evaporated and the leaf turns a dark brown or black. It is at this stage that the aroma changes from that of a pungent plant to the familiar earthy tea perfume. The black tea is ejected from the hot chamber into chests. Next it is sorted into grades, or leaf particle sizes, by being passed through a series of wire mesh sifts of varying sizes into containers. It is then weighed and packed into chests or "bags" for loading onto pallets. The bigger curly leaves are used for loose-leaf packet tea while the finer particles are used for tea-bags.

Factory tea-tasters will taste the finished "make" to ensure that no mistakes have been made during the manufacture or that the tea has not been tainted by anything within the factory. After each make the tea factory is washed from top to bottom to ensure that the character of the completed make does not transmit to the next make of tea.

Are all teas made the same?

The three principal categories of teas—black, green and oolong—all originate from the same plant, Camellia sinensis. By contrast, herbal teas are not technically teas but infusions of herbs or plants other than tea plants. In all these cases (except herbal teas) the green leaf that is plucked from the tea bush is further processed.

Black tea is fermented, whereas green tea is not fermented and oolong tea is semi-fermented. Varying the processing techniques produces the three distinct types of tea: green (unfermented and likened to white wine), black (a rich, fully fermented product likened to red wine) and oolong, (fermented for a short time and is known as brown or, by the Chinese, red tea). The variations in character reflect the different geographical and climatic conditions in which the tea plant is grown. Tea flavour is also often altered by the introduction of flavour agents (eg. Earl Grey tea is produced by adding Oil of Bergamot to black tea).

Although leaves for green, oolong and black tea can be produced from the same bush, today’s tea growers tend to specialise in one variety. Australia’s tea production is almost 100% focused on black tea.

Black tea processing uses as raw material the young shoot of the tea plant, comprising the terminal bud and the two adjacent leaves. This is known as the "flush". The "flush" is processed in distinct stages: withering, rolling, fermenting, firing (drying) and grading. Each stage involves characteristic changes in the physical and biochemical composition of the leaves and the cumulative effects of these changes are ultimately reflected in the quality of the finished black tea product.

Black tea is currently manufactured in two ways—by the orthodox and the CTC processes, the latter being more common. Most of the tea in India is manufactured using the CTC process. In black tea manufacturing, the prime objective is to condition the freshly plucked green tea leaves for fermentation, attain optimum fermentation and then quickly stop the fermentation process. This is achieved by rupturing the leaf cells to release enzymes and expose them to oxygen to initiate the process of oxidation. As soon as optimum fermentation is achieved, the leaf mass is passed through hot air which deactivates the enzymes and stops oxidation.  

Source: Australia Tea Industry Forum