Coffee comes from the genus Coffea, a member of the Rubiaceae family, comprising more than 500 genera and 6,000 tropical trees and shrubs. However, Coffea is vastly more economically important than any other member of this botanical family.

The eighteenth century Swedish botanist, Carolus Linnaeus (1707 - 1778), who first classified the Rubiaceae genus, identified over 60 different varieties of Coffea. However, because of the vast differences between coffee plants and seeds, botanists still disagree today over the number of unique varieties. Most would agree, however, that Ethiopia has distinctly more genetic varieties than any other country. In fact, new varieties are still being discovered in its high altitude forests. Only a few years ago, a new variety was discovered that did not contain caffeine.

Coffee is a tropical plant which grows between the Tropic of Cancer and the Tropic of Capricorn but requires very specific environmental conditions for commercial cultivation. Temperature, rainfall, sunlight, wind and soils are all important, but requirements vary according to the varieties grown. All coffee needs good drainage, but it can grow on widely different soils, given suitable fertilizer.

Although frost is very rare in the tropics (occurring about once every twenty years), it has disastrous consequences for coffee plants. One night of temperatures below zero degrees Celsius is enough to cause extensive defoliation with little hope of the plant recovering. Altitude and local wind and rainfall conditions may affect this phenomenon - the highest danger from frost being in southern Brazil or, closer to the Equator, at altitudes around 2,000 metres.

Cultivation of coffee trees begins with the seeds being planted in potting soil and kept in nurseries for 9 to 18 months, until they reach a height of 18 to 24 inches.  After that they are transplanted to permanent groves and left for a further year to develop a good root system.  After all that time they are still just about 30 centimetres tall.

After three to four years, when they reach maturity, coffee plants bear fruit in clusters along their branches. The fruit turns red and cherry-like when it is ready to be harvested. Depending on the type of coffee plant, the cherries take between 6 to 11 months to ripen. However, all of the cherries on a plant do not ripen at that same time, making the job of the pickers very laborious.  A picker has to visit each plant several times over the harvesting season in order to collect all the cherries.  Genetically modified varieties, where all the cherries ripen at the same time, have recently been introduced in the Americas.

The traditional way to grow coffee trees is to grow compatible trees nearby, to keep the coffee trees and their developing fruit from the sun. Often these are economic crops as well such as bananas which mimic the natural habitat of coffee. The modern techniques are to use irrigation systems and fertilizers. Coffee is grown on both large estates and in the smallest of forest clearings.

Manpower availability affects the planting style determining plant density. Also field operations like pruning and weed control are implemented in different ways according to local labour situations. Pruning is seldom implemented due to the high labour requirement - just when shrubs tend to grow too tall to be harvested without the aid of a ladder are the higher branches cut to keep the plant no taller than around 2 metres.

Many pests and diseases can affect the coffee plant or its fruits, the most dangerous being:

• Fungal diseases

• Nematodes infestation of the roots

• Insect attack of the leaves

• Insect attack of the cherries

• Fungal disease of the seed

Pest control is important to improve yield and product quality, and often even to assure the very plantation's survival.

Addition of manure or chemical fertilizers is seldom used in coffee farms. Sometimes just cut weeds and cherry pulp deriving from crop processing are spread between rows of plants. Of course soil depletion follows if many years of coffee growing are not alternated with different crops.

There are about 25 major species within Coffea, but the typical coffee drinker is likely to be familiar with just two: Coffea Arabica and Coffea Canephora  (var. Robusta). Arabica is autogamous, that is to say, capable of fertilising itself, whereas Robusta is allogamous and has to be fertilised.

Arabica represents approximately 70 percent of the world's coffee production. Typica and Bourbon are the two best known varieties of Coffea Arabica, but many strains have been developed, including Abyssinica (Ethiopia), Caturra (Brazil and Colombia), Mundo Novo (Brazil), Tico (Central America), the dwarf San Ramon and Jamaican Blue Mountain.

Coffea Arabica is a spontaneous mutation of pre-existing races which doubled the number of chromosomes in the cell. As a result it has 44 chromosomes compared with 22 for most other coffee varieties.

The Arabica plant is an evergreen, typically a large bush with dark green, oval shaped leaves that can reach a height of 14 to 20 feet fully grown. On plantations the plants are kept at a height of about two to three metres to facilitate harvesting and nourish heavy bearing of berries.

After planting, Arabica trees mature in three to four years, when they produce their first crop. The Arabica plant can continue to produce fruits for about 50 years although the fruit yield decreases significantly after about 30. Arabica trees prefer a seasonal climate of 60-75 degrees Fahrenheit and an annual rainfall of 60 inches.

Primary, non-renewable branches grow from the trunk at an average distance of 15 cm. The plants have taproots that are not very deep. The bright green leaves are shiny on top and dull on the underside; they vary from 5 to 20 cm in length and come to a point. Its branches carry bouquets of 5-12 small, white flowers with a jasmine-like fragrance.

The five-petal flowers fade quickly as they wilt as soon as fertilisation has taken place. They are quickly replaced by others, however. Once fertilised they give way to the coffee cherry; these are oval-shaped berries with, usually, two beans side-by-side with their flat sides together. When only one bean develops from a cherry it is called a peaberry. Each tree can produce between 1 and 12 pounds of coffee a year, depending on soil, climate and many other factors. At high altitudes the plants generally blossom once, while in the lower-lying areas where there are no great seasonal changes the plants blossom several times a year - so that there are almost always fruits on the plants.

A hybrid of Arabica, Maragogype - called the elephant bean because of its large size - originated from the Maragogype County in the Bahia state of Brazil. Today it is grown in Guatemala, Mexico, Nicaragua, Honduras, El Salvador, Brazil and Zaire.

Coffea Canephora provides the Robusta beans. Robusta, which can grow up to 32 feet in height as a shrub or tree, has a shallow root system. The fruits are round and take nearly a year to mature. The seeds are rounder and smaller than Arabica beans. Robusta coffee was discovered in the Congo in 1898 and has become widespread since then - representing about 1/4 of the world's coffee production. It is grown in West and Central Africa, throughout Southeast Asia, and parts of South America including Brazil, where it is known as Conilon.

Robusta trees produce their first crop 3 to 4 years after planting and they remain fruitful for 20 to 30 years. The trees prefer equatorial conditions with temperatures between 75 and 85 degrees Fahrenheit and an annual rainfall of 60 inches.

Robusta tends to be a hardier, more disease-resistant bean than Arabica,less expensive to maintain and produces a higher yield. Consequently Robustas are used for the less expensive canned and instant coffees.

Arabica coffee grows best at high altitudes (from 1500m to 2500m) while Robusta coffee does best in lowlands such as rainforests. Before roasting, the colour of Robusta beans are yellow to light brown in appearance whereas Arabica are green with silver/bluish shades.

Some differences between Arabica and Robusta:

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