In the classification system of the vegetable kingdom created by the Swedish botanist Carl Linneo, coffee was classified in the family of "rubiacee", that gathers 4500 varieties among which 60 species belong to the coffee group. Of the 60 coffee plants species, only 25 are the most commercial for the fruits but only the first four of them have a prominent position in the trade of coffee beans: Coffea Arabica, Coffea Robusta, Coffea Liberica and Coffea Excelsa.

Coffea Arabica

Cultivated and selected since some centuries ago. The most know is the Moka variety, mostly cultivated in Arabia, whose little beans have an intense aromatic smell. Their characteristic colour is copper green, and their shape is flattened and lengthened. Different varieties are the "Tipica", the "Bourbon" diffused in Brazil and the "Maragogype", appreciated for its bigger beans.
The Arabica plants prosper in lands endowed with minerals, as the ones of volcanic origin, located over 600 meters high. The ideal climate must be around 20°C.
The cultivation of different species was introduced from the end of the ninth century, after the diseases that, in different areas, affected and decimated the Coffea Arabica. From that moment different species were chosen and selected, able to produce beans to be successfully introduced into the international market. The following are the most interesting ones for the production of coffee:

Coffea Robusta

Similar to the Coffea Arabica, its branches bend toward the ground, as an umbrella. During the year the blooming is continuous. Its round beans are smaller, but richer in caffeine compared to the previous species and, once they are roasted, they are very odorous.
This species, that also vegetates in the lowland, had a great luck in the commerce. Discovered in Congo, it is currently much cultivated because, besides the production abundance and the cheaper equipment costs, it shows a strong resistance to the diseases, vegetating in comfortless conditions.
Some varieties obtained by crosses of "Canephora", to which Robusta belongs, are diffused in Indonesia, Uganda, India and in the west side of Africa. Moreover, "Arabusta" was obtained, crossing the two Coffee Arabica and Robusta.

Coffea Liberica

Coming from the forests of Liberia and Ivory Coast, it is a beautiful long-life plant, strong, luxuriant, with fruits and seeds dimension that is almost the double of the Arabica ones, and more resistant to parasites attacks. It is a plant that needs a high temperature and abundant water. Due to these characteristics, the Coffea Liberica is chosen as graft-holder to obtain, by cross, new varieties that are mostly present in the Ivory Coast and in Madagascar.
Its beans, even if of a lower quality, give a odorous and pleasant coffee. Some decades ago, its taste was mostly appreciated in the Scandinavian countries.

Coffea Excelsa

Discovered in 1904, this species resists to the diseases and dryness. It has a high yield and its aged beans give a coffee with odorous and pleasant taste, similar to the one of Coffea Arabica.

The four above described species are the most important ones as far as cultivation yield is concerned. The following ones are less suitable and yielding:

Coffea Stenophylla

Cultivated in Guinea, Sierra Leone and Ivory Coast, it is resistant to dryness. The smell of its beans is comparable to the one of Tea, but the taste of the drink does not match the palate of all the tasters. Some specimen are located in botanic gardens.

Coffea Mauritiana

A bitter and stirring drink is obtained from this coffea.

Coffea Racemosa

Plant with fleeting leafs during the dry season, its foliation starts during the rain season. Its coffee is poor of caffeine but very odorous.

Coffea Congencis

Coming from the banks of Congo, it produces a good quality coffee but the shrub is not very productive.

Coffea Dewevrei

It comes from the forests of Congo Belgian.

Coffea Neo-Arnoldiana

Also selected in Congo, it has a high yield.

Coffea Abeokutoe

Cultivated in the Ivory Coast, its beans remind of the Coffea Arabica.

Coffea Dybowskii

It is the group of Eucoffea of inter-tropical Africa.

Other varieties of Coffea are not yielding for cultivation. But some species are cultivated in some countries: Kouilou, Sankuru, Uganda, Niauli.