Edible uses

Notes

The leaves are infused in hot water and used as the drink that is commonly known as tea. It is widely drunk in many areas of the world. Green tea is made from the steamed and dried leaves, whilst black tea (the form most commonly drunk in the west) is made from leaves that have been fermented and then dried[1][2]. Tea contains polyphenols, these are antioxidants that help to protect the body against heart diseases, stroke and cancer[2]. It also contains the stimulant caffeine which, when taken in excess, can cause sleeplessness and irritability and also, through its action as a diuretic, act to remove nutrients from the body. Tea is also rich in tannin and is a possible cause of oesophageal cancer[2]. Cold tea is sometimes used as a soaking liquid to flavour dried fruit[2]. One report says that the leaves are used as a boiled vegetable[3]. The leaves contain about 25.7% protein, 6.5% fat, 40.8% carbohydrate, 5% ash, 3.3% caffeine, 12.9% tannin[3].

Terminal sprouts with 2-3 leaves are usually hand-plucked, 10 kg of green shoots (75-80% water) produce about 2.5 kg dried tea[4]. The bushes are plucked every 7-15 days, depending on the development of the tender shoots. Leaves that are slow in development always make a better flavoured product[4]. Various techniques are used to produce black teas, usually during July and August when solar heat is most intense. Freshly picked leaves are spread very thinly and evenly on trays and placed in the sun until the leaves become very flaccid, requiring 13 hours or more, depending on heat and humidity. Other types of black teas are made by withering the leaves, rolling them into a ball and allowing to ferment in a damp place for 3-6 hours, at which time the ball turns a yellowish copper colour, with an agreeable fruity one[4]. If this stage goes too far, the leaves become sour and unfit for tea. After fermenting, the ball is broken up and the leaves spread out on trays and dried in oven until leaves are brittle and have slight odour of tea[4]. Tea is then stored in air-tight tin boxes or cans. As soon as harvested, leaves are steamed or heated to dry the natural sap and prevent oxidation to produce green tea. Still soft and pliable after the initial treatment, the leaves are then rolled and subjected to further firing. Thus dried, the leaves are sorted into various grades of green tea[4]. The flowers are made into 'tempura' using the edible oil that is obtained from the seed[1]. A clear golden-yellow edible oil resembling sasanqua oil is obtained from the seed[1][4]. The oil needs to be refined before it is eaten. An essential oil distilled from the fermented dried leaves is used as a commercial food flavouring[2]. Tea extract is used as a flavour in alcoholic beverages, frozen dairy desserts, candy, baked goods, gelatines, and puddings[4].

Tea is a potential source of food colours (black, green, orange, yellow, etc.)[4].
Material uses
An essential oil is distilled from the fermented and dried leaves[2]. It is used in perfumery and in commercial food flavouring[2].

A non-drying oil is obtained from the seeds. Refined teaseed oil, made by removing the free fatty acids with caustic soda, then bleaching the oil with Fuller's earth and a sprinkling of bone black, makes an oil suitable for use in manufacture of sanctuary or signal oil for burning purposes, and in all respects is considered a favourable substitute for rapeseed, olive, or lard oils. The oil is different from cottonseed, corn, or sesame oils in that it is a non-drying oil and is not subject to oxidation changes, thus making it very suitable for use in the textile industry; it remains liquid below -18deg.C[4]. A grey dye is obtained from the pink or red petals[5]. The leaves contain 13 - 18% tannin[6]. The leaves also contain quercetin, a dyestuff that, when found in other plants, is much used as a dye[6]. The quantity of quercetin is not given[K].

Wood - moderately hard, close and even grained. It is very good for walking sticks[7].

Unknown part

Medicinal uses(Warning!)

The tea plant is commonly used in Chinese herbalism, where it is considered to be one of the 50 fundamental herbs[8]. Modern research has shown that there are many health benefits to drinking tea, including its ability to protect the drinker from certain heart diseases. It has also been shown that drinking tea can protect the teeth from decay[9], because of the fluoride naturally occurring in the tea[K]. However, the tea also contains some tannin, which is suspected of being carcinogenic[4].

The leaves are cardiotonic, diuretic, expectorant, stimulant and astringent[10][11][12][8][13][4]. They exert a decided influence over the nervous system, giving a feeling of comfort and exhilaration, but also producing an unnatural wakefulness when taken in large doses[10]. They are used internally in the treatment of diarrhoea, dysentery, hepatitis and gastro-enteritis[8][2]. Tea is reportedly effective in clinical treatment of amoebic dysentery, bacterial dysentery, gastro-enteritis, and hepatitis. It has also been reported to have antiatherosclerotic effects and vitamin P activity[4]. Excessive use, however, can lead to dizziness, constipation, constipation, indigestion, palpitations and insomnia[2]. Externally, they are used as a poultice or wash to treat cuts, burns, bruises, insect bites, ophthalmia, swellings etc[8][2][14]. Only the very young leaves and leaf buds are used, these can be harvested throughout the growing season from plants over three years old and are dried for later use[2].

Teabags have been poulticed onto baggy or tired eyes, compressed onto headache, or used to bathe sunburn[4].

Ecology

Ecosystem niche/layer

Ecological Functions

Nothing listed.

Forage

Nothing listed.

Shelter

Nothing listed.

Propagation

Seed - can be sown as soon as it is ripe in a greenhouse[15]. Stored seed should be pre-soaked for 24 hours in warm water and the hard covering around the micropyle should be filed down to leave a thin covering[16][15][17]. It usually germinates in 1 - 3 months at 23°c[17]. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in light shade in the greenhouse for at least their first winter. Plant them out into their permanent positions when they are more than 15cm tall and give them some protection from winter cold for their first year or three outdoors[K]. Seedlings take 4 - 12 years before they start to produce seed[4].

There are approximately 500 seeds per kilo[4]. Cuttings of almost ripe wood, 10 - 15cm with a heel, August/September in a shaded frame. High percentage but slow[16]. Cuttings of firm wood, 7 - 10cm with a heel, end of June in a frame[18][16]. Keep in a cool greenhouse for the first year[18].

Leaf-bud cuttings, July/August in a frame.

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Cultivation

Prefers a woodland soil but thrives in a warm open well-drained loam if leafmould is added[19][18][20]. A calcifuge plant, preferring a pH between 5 and 7[18][20]. Prefers the partial shade of a light woodland or a woodland clearing[21][20]. Forms grown in this country are slow-growing[22]. Tea is reported to tolerate an annual precipitation of 70 to 310cm, an average annual temperature range of 14 to 27°C and a pH in the range of 4.5 to 7.3[4].

This species is not hardy in the colder areas of the country, it tolerates temperatures down to between -5 and -10°c[20]. It prefers a wet summer and a cool but not very frosty dry winter[20]. The fragrant flowers are very attractive to insects, particularly moths[22]. Plants are not very self-compatible, self-fertilized flowers produce few seeds and these are of low viability[20]. A very ornamental plant[19], it is widely cultivated in tropical and warm temperate areas for its leaves which are used to make China tea[19]. There are many named varieties[1] and new hardier forms are being produced in China for growing in colder areas of the country[23]. The Chinese form, known as 'Hsüeh-ch'a', is said to grow in areas within the snow limit on the mountains of Lingchiangfu in Yunnan province[24].

Additional information for Green Tea

 tags

Tea