Several species of shrub of the genus Coffea produce the berries from which coffee is extracted. The two main species cultivated commercially are Coffea canephora - better known as 'robusta' - and Coffea arabica. Both are cultivated at the Ijen Plateau.
Arabica is native to the southwestern highlands of Ethiopia and the Boma Plateau in southeastern Sudan and possibly Mount Marsabit in northern Kenya. The robusta strain arrived in Java around 1900. Canephora is native to western and central subsaharan Africa, from Guinea to the Uganda and southern Sudan. In Java both species are commonly used over the years. At the plantation Blawan and Kalisat at the Ijen Plateau mainly Arabica is grown.
Coffee fields at Ijen Plateau
Sometimes fields that look empty aren't. Old coffee trees are cut about 50 centimeters above the soil. This is also called the Ijen Pruning System. The plants are cut because production dropped. But, their root system is still very strong. These coffee plants will sprout again and come back into production. At the Ijen Plateau the coffee plantations are diversifying, in particular in Kalisat. Nowadays, oranges and macadamia nuts are inter-cropped with coffee. Otherwise, strawberries are a sold as far as Bali.
Greenhouses and modern experiments
Because of problems with the roots of the arabica coffee plants, a grafting experiment - based on results of the coffee plantation in Jember - was started a few years ago. Robusta forms the stem, while arabica is on top.
Large differences in productivity
Only Coffea arabica and Coffea canephora are commercialized out of the more than 60 existing species. From each species there are several varieties with different flavours, but also large differences in terms of productivity. Productivity can range between 3 to 12 tonnes per hectare. While arabica can fertilize itself, robusta needs a male and a female tree to reproduce. The quality of the coffee depends on several factors: botanical species and variety, terrain, temperature, altitude, sun exposure, amount of light (shade), water (irrigation) and wind.
The flower of the coffee plant looks like a jasmine flower. Therefore, the tree bears the name 'Arabian jasmine' until the 17th century. The flower brings a stone fruit which needs 6 to 9 months to mature. Normally coffee blossoms twice a year. But under the influence of humidity, the coffee plant can blossom up to 8 times a year. This explains why in one twig different stages of maturity may reside. The ripe fruit is red, shiny and firm. Immature fruits give the coffee a sharp flavor, while fruits that are too ripe taste bitter and unpleasant.
Coffee plants at the Ijen Plateau can easily reach an age of 40. But, productivity is correlated to age. Not only age interferes with productivity, bears in which a coffee plant bears many beans are alternated by those with less beans. The harvest depends also on location - mainly height - and climate. On average the production at the Ijen Plateau is between 600 and 1000 kg per hectare.
Methods to harvest coffee: hand-picked at the Ijen Plateau
1. Stripping: the branch is ripped of all fruits - both ripe and unripe - and flowers
2. Combing: with a special comb, with smooth and spaced teeth, are 'combed' of the branch. The ripe red berries fall off, while the green berries linger
3. Mechanical: tractors with combs remove the berries, but also the flowers and the leaves. In Brazil this method is widely used and is effective. But the quality is low, as is the case with stripping
4. Picking: only the ripe berries are hand-picked.
At the plantations at the Ijen Plateau method 4, hand picking, is used. Labour in Java is still very cheap. Besides, many companies prefer to offer more people a job instead of only a few in combination with mechanization. Most coffee is picked in the months June and July, in August the daily harvest already declines.
Fungi threaten arabica
Robusta is less susceptible to disease than arabica and can be cultivated in lower altitudes and warmer climates.