Tea

Description

Tea, Camellia sinensis, is a tree or small shrub in the family Theaceae grown for its leaves which are used to make beverages. The tea plant is branching with alternate elliptical leaves. The leaves are leathery in texture, matte green in color and have serrated edges. The tea plant can take the form of a tree with a bowl-shaped canopy but is usually pruned under cultivation to be smaller and shrub-like. The plant produces fragrant white flower singly or in small clusters. Tea tree can reach up to 15 m (49 ft) in height and can live anywhere between 30 and 50 years. The plant originates from China.


Uses

Tea leaves are usually infused with boiling water to produce an infused drink. In China, most tea leaves are processed for green tea (little or no fermentation of the leaves) whereas most Assam tea is processed for black tea which is manufactured by fermenting and crushing the leaves.


Propagation


Basic requirements
Tea grows best in warm and humid climates. It will tolerate temperatures between 14 and 27°C (57.2–80.6°F) with 18–20°C (64.4–68°F) being optimum. Tea plants will not tolerate frost and mean temperatures should not fall below 13°C (55.4°F) or exceed 29°C (84.2°F). Tea grows optimally in deep, well-draining, tropical red soils with an acidic pH between 4.5 and 6.0. Tea requires an average annual rainfall of 1600 mm per year distributed evenly throughout the growing season. In growing regions that experience a long dry season, tea plants require shading to increase the humidity around the plants.

Propagation
Tea is propagated from seed or rooted leaf cuttings. Good quality seeds are selected by immersing in water for 30 minutes and selecting the seeds which sink. Seeds are commonly germinated by placing them between wet cloths. Seeds which successfully germinate are transferred to a nursery bed to grow for 2–3 years. Before transplanting to the field, the plants are cut back to a height of 15 cm (6.0 in). Leaf cuttings are also used to establish new tea plantations. Single node cuttings are taken from the desired variety and rooted in polyethylene bags containing soil by firmly pressing the stem into the soil. The bags are then placed in a shaded area and watered regularly. New tea plants produced from rooted cuttings are usually planted out in the field after 6–9 months. Tea can be planted as single rows, double rows or as a hedge. Plantations established on slopes are planted on contour rows. Seedlings or cuttings are usually planted 60 cm (24 in) apart, allowing 1.5 m (5 ft) between rows. The tea plants are often interplanted with legumes or grasses to conserve soil moisture and prevent soil erosion. Shade trees are utilized in tea plantations grown at lower altitudes.

General care and maintenance
Newly planted tea plantations must be kept free from weeds while the tea plants establish. Weeding should be done by hand until the canopy closes and shades out weeds. Tea plants should be pruned to encourage the production of lateral branches. Busjes are shaped by tipping and thinning of branches to create the desired shape. Pruning should be maintained throughout the life of the plantation to keep the plants a manageable size and maintain productivity. pruning is best carried out when the plants are dormant where possible. If trees do not have a dormant period then they should be pruned in winter or after the dry period depending on geographic location. The tree clippings can be left in the centers of the rows to acts as an organic mulch. Tea plantations are usually fertilized 2–3 times per year. The amount of each nutrient added to the soil will depend on the soil’s own deficiencies and should ideally be based on the results of soil testing or by testing the leaves for nutrient deficiencies.

Harvesting
Tea is harvested by “plucking” which involves the removal of the youngest leaves at the shoot terminals. The terminal bud is removed along with the two leaves directly below (fine plucking) or the bud and three leaves (coarse plucking). The younger leaves have the best flavor and removing three leaves increases production but diminishes the overall quality by including an older leaf. Tea plants are plucked by hand by grasping the plant between thumb and forefinger and is usually carried out every 7–14 days depending on altitude.


References

CABI Crop Protection Compendium. (2008). Camellia sinensis (tea) datasheet. Available at: http://www.cabi.org/cpc/datasheet/10781. [Accessed 20 April 15]. Paid subscription required.

Crane, J. H. & Balerdi, C. F. (2013). Tea growing in the Florida home landscape. Available at: http://edis.ifas.ufl.edu/pdffiles/HS/.... [Accessed 20 April 15]. Free to access.

Duke, J. A. (1983). Camellia sinensis (L.) Kuntze. Handbook of Energy Crops (Unpublished). Available at: http://www.hort.purdue.edu/newcrop/du.... [Accessed 20 April 15] . Free to access.



Common Pests and Diseases

Algal leaf spot
Cephaleuros virescens

Symptoms
Gray, green or tan raised spots or blotches with green margins on leaves
Cause
Algae
Comments
Disease emergence favored by high temperature and humidity
Management
Avoid overhead irrigation which can spread the disease; provide adequate space between plants to maximize air circulation around foliage; avoid wounding plants; prune out diseases parts of plants by cutting 6 inches below any visible symptoms; application of appropriate protective fungicides should be made in Spring when old leaves drop from plants

Spider mites (Two-spotted spider mite)
Tetranychus urticae

Symptoms
Leaves stippled with yellow; leaves may appear bronzed; webbing covering leaves; mites may be visible as tiny moving dots on the webs or underside of leaves, best viewed using a hand lens; usually not spotted until there are visible symptoms on the plant; leaves turn yellow and may drop from plant
Cause
Arachnid
Comments
Spider mites thrive in dusty conditions; water-stressed plants are more susceptible to attack
Management
In the home garden, spraying plants with a strong jet of water can help reduce buildup of spider mite populations; if mites become problematic apply insecticidal soap to plants; certain chemical insecticides may actually increase mite populations by killing off natural enemies and promoting mite reproduction

Camellia dieback and canker
Glomerella cingulata

Symptoms
Leaves suddenly turning yellow and wilting; branch tips dying; gray blotches on bark and stem which develop into sunken areas (cankers); cankers girdling the stem; parts of plant above cankers losing vigor, wilting and dying; symptoms more pronounced during hot, dry weather
Cause
Fungus
Comments
Fungus can enter plant through wounds
Management
Plant in well draining, acidic soils; remove diseased twigs by cutting several inches below cankered areas and disinfecting tools between cuts; apply appropriate protective fungicides during periods of wet weather or natural leaf drop to protect leaf scars from infection

Camellia flower blight
Ciborinia camelliae

Symptoms
Small, brown, irregular-shaped spots on the flower petals; whole flower turning brown; flowers dropping from plant
Cause
Fungus
Comments
Disease emerges early in Spring during periods of high moisture
Management
Remove all infected flowers from plants; remove all crop debris from around plants; soil drenches with appropriate fungicides can help to reduce the intensity of the disease

Blister blight
Exobasidium vexans

Symptoms
Small, pinhole-size spots on young leaves; spots become transparent, larger, and light brown; blisters on underside of leaves; dark green, water-soaked zones surrounding blisters; blisters may be white and velvety or brown; young stems bent and distorted, may break off or die
Cause
Fungus
Comments
Endemic to all major tea growing regions
Management
Plant tea varieties which are less susceptible to the disease; apply appropriate foliar or systemic fungicides to protect the plants

Horse hair blight
Marasmius crinis-equi

Symptoms
Black threadlike structures resembling horse hair attached to upper branches of plant by small brown discs; leaves drop rapidly from plant
Cause
Fungus
Comments
Fungus spreads to healthy parts of plants by extending hair-like threads
Management
Remove a and destroy all crop debris from around plants; prune out infected or dead branches from the plant canopy

Poria root disease (Red root disease)
Poria hypolateritia

Symptoms
Yellowing foliage; wilting and/or sudden death of part of plant; withered leaves remain attached to the plant for several days; uprooting the bush reveals whitish mycelium and red discoloration of the roots
Cause
Fungus
Comments
Spread by mycelial strands in the soil
Management
Remove any visibly infected bushes and any adjacent plants which are showing signs of yellowing; remove any stumps or trees within infested area; all living and dead roots which are about pencil thickness or more should be removed from the site by digging using a fork; all material collected should be destroyed by burning; bushes surrounding the infested area should be treated with an appropriate fungicide applied as a soil drench; cleared site should be planted with grass for a period of two years before tea is replanted

Tea scale
Fiorinia theae

Symptoms
Pale yellow spots on leaves; entire leaves yellowing; leaves turning brown and dropping prematurely; reduced flower size; adult insect is an oblong shape with a ridge down the center parallel to the sides; the scale is initially bright yellow in color but darkens to a dark brown; insect is mainly found on the undersides of leaves
Cause
Insect
Comments
Management
Light infestations can be scraped off the plant and destroyed or infested leaves can be hand picked; heavier infestations can be treated with a horticultural oil after bloom; appropriate insecticides can be applied but are only effective against scales that are actively crawling

Aphids (Tea aphid)
Toxoptera aurantii

Symptoms
Small soft bodied insects on underside of leaves and/or stems of plant; usually green or yellow in color, but may be pink, brown, red or black depending on species and host plant; if aphid infestation is heavy it may cause leaves to yellow and/or distorted, necrotic spots on leaves and/or stunted shoots; aphids secrete a sticky, sugary substance called honeydew which encourages the growth of sooty mold on the plants
Cause
Insects
Comments
Distinguishing features include the presence of cornicles (tubular structures) which project backwards from the body of the aphid; will generally not move very quickly when disturbed
Management
If aphid population is limited to just a few leaves or shoots then the infestation can be pruned out to provide control; check transplants for aphids before planting; use tolerant varieties if available; sturdy plants can be sprayed with a strong jet of water to knock aphids from leaves; insecticides are generally only required to treat aphids if the infestation is very high - plants generally tolerate low and medium level infestation; insecticidal soaps or oils such as neem or canola oil are usually the best method of control; always check the labels of the products for specific usage guidelines prior to use

Root rot
Phytophthora cinnamomi

Symptoms
Leaves turning yellow; poor plant growth; entire plant wilting; roots discolored; rapid death of plant
Cause
Oomycete
Comments
Disease emergence favors poorly drained, warm soils
Management
Disease is difficult to manage once plants become infected so control methods should focus on protecting plants; always plant tea in well-draining soils which are not as favorable for the survival of the pathogen; application of appropriate fungicides can help to protect plants from infection