The coffee tree
The coffee tree is a shrub with a straight trunk, which can survive for about 50 to 70 years. The first flowers appear during the third year, but production is only profitable from the fifth year onwards. 18th century botanists classified Coffee as a member of the Rubiaceous family. Of around sixty different species of coffee tree, two alone dominate world trade - the Coffea arabica, or, more simply, Arabica, which represents 75% of production; and the Coffea canephora, which is commonly known by the name of the most widespread variety: Robusta.
Here is a list of the three most wellknown coffee plants, all related:
- Arabica (from Ethiopia, known from prehistoric times) beans do best at
altitudes of 3,000 to 6,500 feet where the slower growing process concentrates
their flavors. They have a much more refined flavor and contain about 1 percent
caffeine by weight. Because of its delicate nature, it yields only 1 to 1.5 pounds
of green coffee per year. This is the coffee that specialty roasters search for. It
accounts for about 75% of the world production. Because the arabica tree is
susceptible to disease, frost, and drought, it requires very careful cultivation
with just the right climatic conditions.
- Robusta (from Congo, discovered in 1898) beans come from a high yield
plant that is resistant to disease. It does best at lower elevations and has harsh
flavors. It contains about 2 percent caffeine. It bears more coffee cherries than
the arabica plant. It yields 2 to 3 pounds of green coffee a year. This plant is
used for the lower grades of coffee that are sold in the market. Although generally
not found in gourmet shops, robusta beans are often used in the processing of
soluble (instant) coffees and popular commercial blends.
- Liberica (from Western Africa, of no great importance in coffee trade)
is the third recognized commercial variety, it is also hardy and low-altitude. It
is a minor crop of coffee from Africa and is similar to robusta.
A detailled list about the differences between the Arabica en Robusta bean can be found on this page.
The flowers of the coffee tree
The flowers are white with 5 or 6 petals. The pistil that emerges from the cupule is tipped with delicate stigmas. The shape and scent resemble those of jasmine, and it is for this reason that the coffee tree was called "Arabian Jasmine" in the 17th century.
The flowers form glomerules, or little tufts made up of 8 to 15 elements, at the base of the leaves. They produce the same number of berries, commonly known as cherries because of their colour. The flowers last only a few hours and wilt as soon as fertilisation has taken place: however, others quickly replace them. As a result, it is not uncommon to find leaves, flowers and berries on the tree at the same time! One tree can produce over 30,000 flowers in a year.
The leaves of the coffee tree
The coffee tree is an evergreen with spear-shaped leaves, which are green and shiny on the upper side. As with all Rubiaceous plants, the
leaves grow in pairs on either side of the stem and they are stipulated - that is to say, the two foliaceous organs are to be found at the base of the leaf stalk. The leaves of the Robusta trees are much larger than those of the Arabica.
The cherry is the name usually given to the fruit of the coffee tree. Botanists prefer to call it the "drupe". Green to begin with, the berries ripen over several months, becoming successively yellow, then red, garnet red, and finally almost black.
The ideal time for harvesting is when the berries are red. Inside the drupe, protected by the "mesocarp" or pulp, lie two small beans separated by a groove. These must be extracted and roasted before they can be used for consumption. Coffee is a member of the Rubiaceous family (Gardenias, Quinquina, Garence), it has a lot in common with Jasmine. The plant was first classified in 1753 and there are now about 60 different species, each having different varieties. However, there are two main types: Arabica and Robusta.
Coffee grows on varied soils - volcanic, siliceous clay, alluvial and peat and sand. Like the vine, soil gives a particular character to the same botanical species and different "Vintages" arise. Soil must be deep (roots are 1 to 2 metres) and acid (pH 4.5 to 6).
Important growing factors are:
- Avoiding excessive cold and heat.
- 1200-1500mm of rain per annum.
- A few hours of light per day.
- No strong winds.
- Altitude - The higher the better.
Coffee grows between 28 degrees North and 30 degrees South; so growing areas include Central America, Caribbean, Brazil, West Africa, East Africa and Yemen, Madagascar, India, Indonesia and Vietnam.