Green tea

24.05.17

There are three main types of tea produced in the world — black, green and oolong. The difference in types is based to some extent on plant variety and most significantly on processing technique.

Tea is produced by harvesting the fresh shoots of the tea plant, an evergreen shrub with dark green glossy leaves. In its natural state the tea plant could grow to five metres tall but in commercial plantations, it is kept to a height of about one metre due to ongoing harvesting. Tea plantations are expected to have a productive life of 50–100 years; and some tea trees in China are reported to be 700–1000 years old.

Overview

The tea plant belongs to the genus Camellia, as do the species of Camellia commonly found in gardens. Black tea is produced primarily from the plant Camellia sinensis var. assamica, which is native to the Assam region of India, and its harvested leaves are fermented and dried, resulting in a brown leaf.

Green tea is produced mostly from Camellia sinensis var. sinensis, native to China, and its harvested leaves are steamed or roasted to prevent fermentation and then dried, resulting, in a green leaf.

Oolong tea is also produced from Camellia sinensis var. sinensis but the harvested leaves are only partially fermented before drying.

While three main types of tea are recognised, globally there are many geographical variations of the main tea plant varieties, and many cultural variations on procedures to make tea.

Global production of tea, averaged over three years to 2016, was 7.9 million tonnes. While there are no figures available on production of different types, general industry estimates are that 72% is black tea, 25% is green and 3% is oolong.

In Australia, black tea is produced in northern Australia from plants descended from several sources of seed, most likely Camellia sinensis var. assamica. Existing plantings are based on suitable provenance stock rather than specific varieties. Japanese green tea is grown in the southern half of Australia from specific Japanese varieties of Camellia sinensis var. sinensis. These varieties are a smaller and slower growing plant, with smaller leaves and more cold tolerance than ‘black tea’ varieties. Green tea varieties require a dormant period during winter to produce the important first flush of growth in mid to late spring, and the plants have three to four flushes of active shoot growth per year.

Consumption of green tea is growing around the world, as the health benefits of the drink are discovered and promoted. The production of Japanese green tea in Australia is a small niche industry, with nearly all growers in north east Victoria supplying a Japanese beverage company that has established itself in the growing region. In New South Wales, a Japanese company has established a farm and processing facility on the New South Wales central coast, to supply the Japanese market.

Facts and figures

  • Tea is the second most consumed drink in the world after water, with an estimated 18–20 billion cups of tea consumed every day
  • Green tea plants can be harvested 3–5 times a season
  • Proximity to a processing facility is essential for tea production
  • Green tea originated in south west China and has been used as a beverage and medicine in China since 2700 BC
  • Britain imported green tea from China for over 200 years but in the 1830s native tea plants were discovered in the British colony of India and the British have controlled the world marketing of black tea since

Production status

There are two main processors of green tea. One in Victoria that contracts 11 growers in the region, and one in New South Wales where there is one tea plantation, which is owned by the company that has also developed a processing plant in the same area.

Commercial plantings of green tea in Australia total less than 80 hectares and production in 2011–12 was 1,300 tonnes of wet green leaf. In the longer-term, both processors are hopeful of increasing production. Trial or small plantings also exist in Tasmania, Western Australia and Queensland.

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Map of current and potential growing regions

Uses

Tea is consumed as an infusion made from adding boiled then slightly cooled water to tea leaves; and is consumed by people around the world. Green tea is a drink that is yellow to green in colour, and quite subtle in its flavour.

Green tea is also manufactured as a cold, ready-to-drink beverage and retailed in cans and plastic bottles. Green tea leaf can also be made into a powder for use as an ingredient in sweet and savoury cooking.

In traditional Chinese and Indian medicine, practitioners used green tea as a stimulant, a diuretic (to help rid the body of excess fluid), an astringent (to control bleeding and help heal wounds), and to improve heart health. Other traditional uses of green tea include treating gas, regulating body temperature and blood sugar, promoting digestion, and improving mental processes.

Modern medical research largely attributes the health benefits of tea (black and green) to the high content of flavonoids — plant-derived compounds that are antioxidants. The antioxidants in all teas can help block the oxidation of LDL (bad) cholesterol, increase HDL (good) cholesterol, improve artery function, and reduce heart disease.

Green tea is also the best food source of antioxidant compounds called catechins. In test tubes, catechins are more powerful than vitamins C and E in halting oxidative damage to cells and resisting cold and flu viruses, and they appear to have other disease-fighting properties. Studies have found an association between consuming green tea and a reduced risk for several cancers.

Production Requirements

Growing regions

Green tea is mainly produced in the alpine valleys of north east Victoria and there is one commercial plantation on the central coast of New South Wales. Small plantings have been established on a trial basis south of Perth in Western Australia, south of Hobart in Tasmania and in Queensland.

The quality of the tea leaf can deteriorate quickly after harvest and therefore harvested leaf must be able to be delivered to the processor within a few hours of harvest. Unless the tea is going to be processed on farm, proximity to a processor and suitable transfer bins/trailers are key considerations when determining the suitability of a site for tea production.

Soil type

Japanese green tea requires well-drained soils with a pH(water) range of 4.5–6.0 and friable soil depth of 60–100cm.

Climate

Japanese green tea is grown from tea varieties developed and grown in Japan, and therefore best suited to a temperate climate. The plant requires a period of cold-induced dormancy to optimally produce the compounds that give green tea its unique flavour. Although the plant withstands cold winters, the fresh new growth in early spring is sensitive to frost, and the first (and most valuable) harvest can be lost.

A long warm summer encourages continued growth, allowing for several harvests. While high temperatures may inhibit growth, production has not suffered in north east Victoria, where temperatures over 35°C occur.

Green tea requires summer rainfall of 1,000mm to support its active summer growth, however current Australian plantations are irrigated to ensure adequate water supply and compensate for any rainfall deficiency.

Varieties

The varieties of green tea (Camellia sinensis var. sinensis) grown in Australia are the Japanese tea varieties: Yabukita and Sayamakoari most frequently, and to a lesser extent Okumidori and Meiryoku.

There are many other strains and clones of the species Camellia sinensis var. sinensis, however information about these in the Australian context is not available.

Planting and crop management

The production of green tea is an intensive horticultural enterprise, particularly if targeting the Japanese market. Young plants require a lot of attention during the establishment phase, however once established plants can produce commercial harvests for up to 30 years, at least. If using mechanical production techniques, a production area of at least 10 hectares is considered economically viable.

Site preparation is important to create a deep and well-drained soil bed, to maximise root development of the planting, as well as providing the opportunity to make soil amendments, such as organic matter and amending soil pH. Site preparation is also the time to control weeds through appropriate herbicide applications or growing an annual crop for green mulch.

The width of raised beds and spacing between plant rows should be determined according to the harvester (and other equipment to be used). Once the plants are mature, there is only wheel space between the hedges.

A tea plantation may be established when the soil moisture levels are optimal to avoid soil structural damage. In Victoria this is in spring when the soil becomes dry enough to work or in autumn after the break (first rains). Tea plants are sourced as rooted cuttings from the desired variety, and generally planted using a modified vegetable or tobacco planter. Tea strikes readily and growers are able to propagate their own planting stock. Alternatively, a specialised nursery could be engaged to strike plants.

Canopy management is important during establishment, and involves repeated, well-timed pruning (skiffing) to promote branching and encourage the plant to grow as a low, spreading bush. During establishment, weed control is also critical and weed monitoring must be vigilant (see Weeds, pests and diseases).

Japanese green tea plantations require a balanced fertiliser program, based on nitrogen, phosphorus and potassium, however the program should be refined on the basis of leaf and soil analyses. Nitrogen is a critical component to support the vigorous new growth after harvest and to form the leaf chemical compounds that contribute to high quality. Fertiliser applied through irrigation lines enables targeted and well-timed application for optimum growth while restricting run off and leaching.

Unless rainfall exceeds 1,000mm in summer, irrigation will be required to maintain growth and production throughout the growing season. Depending on location and season, 4–5ML/ha are required for the summer period. Drip irrigation is proving a suitable form of irrigation.

Frost protection measures, including temperature activated sprinkler systems or fans, have proven useful for protecting early spring growth against frost in areas where late frost is a risk. Frost protection in early spring is critical as the first harvest of the season attracts a premium price.

Weeds, pests, and diseases

Weeds can contaminate the quality of the tea harvested from the crop. Site preparation is a critical time to control weeds through appropriate herbicide applications or growing an annual crop. During establishment, weed control is also critical and weed monitoring must be vigilant. Weeds can be controlled by a combination of targeted herbicide treatment, manual removal and inter-row mowing. Once the canopy closes over, it is not possible to use herbicides or cultivate between the rows, however the dense canopy provides strong competition for weeds.

Tea grown in Australia was considered relatively free of insect pests and diseases. A combination of strict quarantine regulations associated with the importation of tea plants and Australian climatic conditions inhibit the prevalence of pests and diseases.

Observations of insect pests in tea crops have found more beneficial insects than potentially damaging insects. Further, a small amount of insect damage to leaves will generally not affect the quality of tea produced.

In addition, vertebrate pests (e.g. rabbits) must be excluded from the establishing crop.

Infrastructure Requirements

A tea plantation for producing green tea will require fencing (and vertebrate pest exclusion) and the installation of an irrigation system. General farm equipment will be required for site preparation, bed forming and weed management during the establishment phase.

As tea is a long-term crop, access to, rather than purchase of planting equipment may be preferable. Tea crops have been successfully planted using modified vegetable or tobacco planters.

During the establishment phase, the plants need to be trimmed into hedgerows. There are several types of machine available for this from hand-held, two-man sickle bar trimmers, specialised ride-on mowers, to using harvesters fitted with trimming rather than harvesting blades. The machine used for trimming throughout the establishment of the plantation will also be used for skiffing — a pruning operation conducted 40 days before harvest to ensure a uniform plant material is harvested.

A mechanical harvester is required for harvesting. It is a self-propelled machine that straddles the hedges. Bins for collection of harvested material will also be required. If any equipment is to be towed in the established crop, the equipment and tractor must be over-hedge style vehicles.

There are various arrangements in terms of acquiring and owning machinery. For example, several growers in north east Victoria have adapted machinery used in hops and tobacco production; and groups of several growers have purchased harvesters under cooperative arrangements.

The requirement for on-farm processing facilities will depend on marketing arrangements. Growers choosing to process their leaf will require purpose-built processing equipment to steam, roll and dry the leaf; as well as packaging and storage facilities.

Harvesting & Processing

The first harvest from green tea is possible four years after planting, with plants reaching their mature size six years after planting. At maturity, yields of up to 18t/ha could be expected.

Depending on plant vigour and growing season, three to four harvests are possible, spaced approximately six weeks apart starting in late spring (October in New South Wales, November in Victoria). Harvesting is carried out mechanically using specialised equipment that straddles the hedgerows.

The time of harvest determines the quality of the tea produced, and the leaf from the first harvest of the season contains higher levels of nitrogen and other nutrients, commanding a price premium over tea from subsequent harvests.

Once harvested the leaf must be processed quickly to prevent deterioration in the quality of the leaf. Unless being processed on farm, leaves should be delivered to a processing plant within a few hours of harvest, and/or harvested leaf should be stored in specialised transport bins that are designed to maintain leaf quality throughout the delivery phase.

Factory processing of green tea involves many steps that involve steaming, rolling and drying the leaf. The fresh leaves are first steamed to destroy enzymes that cause the blackening (fermentation) of the harvested leaf, giving the leaf its typical green colour, aroma and the mouth-feel of tea. The process can last for up to two minutes and reduces the water content of the leaves to 75%.

The leaves are then transferred to the primary drying tea-roller, which twists and dries leaf at high temperatures for 40–50 minutes, further reducing the water content to about 50%. Leaves are then transferred to the secondary drying tea-roller, which presses and twists the leaves, breaking up their cells, producing an even distribution of water content, and dries and rolls the leaves to produce the characteristic shape and aroma of green tea.

The tea is then transferred to a tea drier, which reduces the water content to around 5%, producing araicha or crude tea, which is then further refined and blended to produce the final green tea product. On-farm processing may use a combination of specialised equipment and traditional manual techniques.

The dried leaves may be further processed by way of roasting and having other ingredients added, to make a range of green tea products. Processors value-add green tea by packing the tea into tea bags and making ready-to-drink beverages.

Markets & Marketing

Japanese green tea is being produced in north east Victoria and central coast New South Wales at the instigation of Japanese companies looking to find new production regions to fill the deficit between domestic production and consumer demand in Japan.

World trade of green tea, averaged over three years to 2011, was 216,000 tonnes. China exported 72% of tea traded, with other countries trading less than 5% of this total. Morocco was the largest importer at 17%, followed by the United States of America (9%), the Russian Federation (8%) and France, Germany and many African countries importing 3–6% of total trade. Japan also imported about 3% of total trade.

Australian production of green tea is nearly all destined for Japan, through a Japanese company that has instigated the industry in north east Victoria and set up a processing plant in the region. The company has established growing contracts with producers and provides technical advice. Another Japanese company has established a processing plant in the central coast region of New South Wales.

There are a few growers (3-5) in Victoria and Tasmania, who sell their product to Australia-based specialist tea companies, or process their own leaf and sell their product online, at markets and through specialty tea or food stores.

There is also another commercial company that, in 2014, was reported to be assisting farmers with trial plantations and was interested in establishing regional cooperative farming and processing facilities.

Risks & Regulations

Risks/Challenges

The main production risk in growing green tea is spring frost damaging the new spring growth on the plants and ruining the first harvest of the season. However, many growers have frost protection measures, including temperature-activated sprinkler systems or frost fans, that have proven useful for protecting early spring growth.

Unless a new grower is contemplating full vertical integration, and plans to process their own product, growers are reliant on one customer to purchase their tea. In Victoria, the industry is well organised and the processor works closely with the growers but the risk remains that global factors or changes to business arrangements could disrupt this relationship. In New South Wales there is only one processor and currently no ‘out-growers’.

Regulatory considerations

There are no regulatory requirements related to the production of tea. Quarantine regulations apply to the importation of plant material for new varieties.

Image Gallery

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Harvesting tea leaves (source Nerada Tea)

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Processed green tea leaves

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Green tea drying