Black tea

24.05.17

Tea is produced by harvesting the fresh shoots of the tea plant, an evergreen shrub or small tree, with dark green glossy leaves and small white flowers. 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

Tea is the second most consumed beverage in the world after water, with an estimated 18–20 billion cups of tea consumed every day. 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.

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 black 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 was 8.3 million tonnes. While there are not figures available on production for different types, general industry estimates are 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’ plants. Green tea varieties require a dormant period 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. Black tea, grown in subtropical and tropical climates, grows and is harvested all year round.

The production of black tea in Australia started with tea plants from Sri Lanka being planted in tropical northern Queensland in the late 1880s. However consecutive natural disasters, labour shortages and finally a tidal wave, meant that the enterprise did not thrive. In the 1970s and 80s commercial interest in tea production expanded on the Atherton Tableland, and almost 90% of Australian black tea is now produced in the region, with the remainder being produced in the Northern Rivers region of New South Wales.

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
Australia has over 500 hectares planted for mainly black tea production, and about 6,000t of fresh leaf was harvested annually
The leaf harvested from plants in northern Australia is used to make black tea
As fresh tea leaves need to be correctly stored within 1.5 hours of harvesting and processed after 12 hours of correct storage, proximity to a processing facility is a key consideration for tea production
Black tea has a stronger flavour, more caffeine and longer shelf life than green tea and was traded as compressed bricks
Britain imported 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
Over 90% of black tea in Australia is produced by one large producer and processor in Queensland. Another relatively large-scale producer and processor operates in New South Wales; and there are a few (less than 10) small-sized operations in both states, producing tea for the large processors or for their own specialty tea products.

There is over 500 hectares planted to tea, and about 6,000t of green leaf harvested. The leaf harvested from plants in northern Australia is used to make black tea.

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 it is consumed by people around the world. Black tea is a brown drink, which is more bitter than green tea due to higher levels of tannins and flavanols. Many people add milk, sugar or other flavourings to black tea.

Black tea is also manufactured as a cold, ready to drink beverage and retailed in cans and plastic bottles.

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.

Production Requirements

Growing regions

Black tea is mainly produced in tropical north Queensland, on the Atherton Tablelands or near the coast; and in the Northern Rivers region of New South Wales.

The quality of the tea leaf can deteriorate quickly, therefore harvested leaf must be able to be delivered to the processor within 1–1.5 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

Tea requires well-drained soils with a pH_(water) range of 4.5–6.0 and friable soil depth of 100cm.

Climate

Tea plants selected for Queensland and northern New South Wales require a mild tropical climate with high rainfall and high relative humidity. The ideal climate would have an annual rainfall of 2,000–4,000mm, distributed throughout the year, and with at least 150mm per month.

The temperature range should be between 12°C and 30°C; and the relative humidity greater than 65% year round. Tea is easily damaged by frost, and frost damaged tips are unable to be used for tea production. Growth is reduced at temperatures greater than 30°C.

Varieties

There are no specific varieties or named strains of tea grown in Australia for the production of black tea. The commercial plantings of tea in tropical and subtropical Queensland have been of seedling origin, rather than vegetative clones. Much of the seed was derived from seed imported into north Queensland in the 1930s, which is believed to be of both Camellia sinensis var. assamica and Camellia sinensis var. sinensis origin. Plantings established in the 1980s have been based on seed imported from Africa and Malaysia.

Several growers in northern Australia have a few mature tea plants outside the plantation that are not harvested. These are kept as provenance stock and used as a seed source for producing new plants. Prospective growers are advised to seek advice on planting material and its sources from horticultural advisors, experienced growers and specialised nurseries.

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

Planting and crop management

The production of tea is an intensive enterprise during the establishment phase, however once established, the crop is relatively low maintenance for a horticultural crop, and the plants can produce commercial harvests for over 50 years.

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 increasing phosphorus levels and correcting soil pH. Site preparation is also the time to control weeds through appropriate herbicide applications or growing an annual crop.

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 is established by planting young trees grown from seed. Trees are planted out at about 30—40cm (12—18 months old) in late summer through to early winter. Plants are planted out in hedges, achieving a plant density of 12,000 to 25,000 plants per hectare.

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).

Tea plantations require a balanced fertiliser program, based on nitrogen, phosphorus, potassium and sulphur, however the program should be refined on the basis of leaf and soil analyses and trace elements included as well. Nitrogen will be a critical component, to support the vigorous new growth after harvest and to form the leaf chemical compounds that contribute to quality of the leaf.

Much of the tea in northern Australia grows in annual rainfall regions around 4,000mm, and therefore irrigation is not required for economic growth and production rates. Tea grown for black tea production has an economic profile more like broadacre cropping rather than intensive horticulture. It would not be economical to set up an irrigation system in a 20–50ha tea crop.

Established plantations will require rejuvenation every 3–4 years, where the bushes are cut back to about one metre in height. A mechanical harvester is used for this operation but trimming blades rather than harvesting blades are used. The cut plant material is left on the floor of the plantation. Maintaining a flat, even plane across the hedgerows is critical for harvest quality, i.e. minimising the amount of woody material in the sample.

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 with weeds.

Tea grown in Australia is relatively free of 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.

Infrastructure Requirements

A tea plantation will require fencing 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 and then periodically throughout the crop’s life, plant height will have to be reduced (rejuvenation). There are several types of machines available for trimming but most growers use their harvester fitted with trimming blades rather than harvesting blades.

A mechanical harvester is required for harvesting. It is a self-propelled machine that straddles the hedges, and has adjustable cutter bars to ensure only the newest growth is harvested. 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.

Tropical-grown tea is harvested 15–16 times per season, therefore effective and timely management is most likely when the growers own their own harvester.

Harvesting & Processing

Black tea may be harvested two years after planting. While most tea in the world is hand plucked, all Australian tea has been mechanically harvested the since the 1960s, and there has been ongoing development and refinement of harvesters in Australia.

Tea is a vigorous crop and harvested throughout the year. About 15 cuts per season is typical, which amounts to about every 20 days in the warmer months, and out to every 30 days in winter. Annual yield would be about 25t/ha of wet green leaf, which translates to about 5.0t/ha of dry leaf. On average, it would take about three days to harvest 50 hectares of crop.

The self-propelled harvester clips young shoots from the top surface of the hedge at regular intervals throughout the year. The leaf is loaded into bulk bins and transported to a processing factory within a few hours of harvest to maintain leaf and product quality. Careful attention is required to cutting height to ensure there is not too much woody material in the harvest. The cutter bars on the harvester are lifted about one centimetre with each harvest, to ensure that only buds and the top few leaves are harvested.

Traditionally tea grown in northern Queensland and the Northern Rivers area of New South Wales has been processed into black tea. Within hours of harvest, the wet green leaf is placed in a thin layer in a perforated trough and with the assistance of air flow, it is withered to reduce moisture content and enable certain chemical changes in the leaf. The leaf is then processed into small particles (macerated), releasing the cell contents from the leaves and allowing it to ferment for a few hours. The leaf material is then dried to 2–3% moisture.

The dried leaves may be further processed by way of blending with imported or other ingredients to make a range of tea products. The larger size tea is packaged to be sold as leaf tea and smaller grade tea is put into tea-bags.

Markets & Marketing

Australia produces almost 1,000 tonnes of processed black tea, exports about 450 tonnes and imports 11,000 tonnes. About 130 tonnes of Chinese-style green tea is produced and exported from the traditional black tea plantations.

Australian black tea is grown and processed by two prominent companies, who sell most of their product in supermarkets, competing against global brands of tea. Their product is sold as leaf tea or tea bags, and between the two, these companies hold about 10% market share by volume.

A number of smaller tea growers sell their product to the main processors, sell to speciality tea companies who blend and package tea, using Australian and imported product, for sale in specialty tea shops and gourmet food outlets; or they may process, brand and market their own tea.

The role of tea is well cemented in all cultures, however in Australia (and many other countries) its consumption is decreasing as consumption of coffee increases. In 2012, coffee surpassed tea as the first choice for an at-home drink among Australians. The report authors, BIS Foodservice, believe the change has been driven largely by less expensive methods to prepare coffee at home, combined with a maturing coffee palette in the community.

The reduced consumption of black tea may be reflected in imports, which have been declining by 3.1% each year since the early 2000s; however green tea imports have increased at 15.8% per year, suggesting the promoted health benefits of green tea are influencing Australian consumers.

Risks & Regulations

Risks/challenges

Tea growers supplying the black tea processors receive relatively low prices for their production. Processed black tea competes against product produced in developing countries that have much lower production costs than Australia. The quality of tea from developing countries is comparable to large-scale Australian tea, therefore a premium cannot be commanded.

While tea is a hardy and vigorous crop to grow, its production can be set back by overcast weather and dry conditions. Some pockets of northern Australia may experience frost, and this can damage new plant growth, making one or a few harvests unsuitable for delivery to the processor.

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.