Market requirements

Two main species of coffee are grown today. “Coffea arabica” accounts around 80% of all production worldwide. Arabica was originally a mid-storey tree from the semi-open forests of highland Ethiopia. It grew in slightly acid, but not highly leached soils. For this reason, it responds to high nutrient regimes and produces high yields. 

The second main species is “Coffea canephora”, commonly known as “Robusta”. It is a bigger tree, with larger leaves and is more robust than Arabica. Developed in the lowland forests of the Congo river basin, Robusta is a mid-storey tree from tall, dense rainforests. It is used to long rainy seasons with only a short dry season and soils that are highly leached, but which have a dense mulch from the rainforest trash. It is a less productive tree, producing smaller beans and an inferior, higher caffeine content beverage. 

Arabica is self-pollinating, whereas Robusta depends upon cross-pollination from adjoining trees. In general, Arabica coffee has better ‘cup quality’ than Robusta coffee.

The Coffee Tree 

The coffee tree, if left unpruned, will grow to a height of 10m. In some countries (e.g. Costa Rica) the coffee cultivars will not exceed 2.5m in height. Common practice is to maintain the crop at a reasonable height for easy picking. Properly pruned and tended trees can have a productive life of 20 years or more.

Seedlings are raised in nurseries. They are usually pre-germinated and grown in compost in nursery beds, or polybags prior to planting out when they reach 20-40cm height. Once established – after 2-3 years – flowering and fruiting become more prolific and the tree starts to produce a commercial crop. 

The flowers, which grow on new wood, in clusters in the axils of the leaves, open 8-12 days after the first significant rains of the wet season. They only last for a couple of days; the floral parts dying away, leaving ovaries to produce the fruit. 

Around 6-8 weeks after the flowers are fertilized, cell division produces pinhead sized fruit. These develop into cherries during a period of rapid expansion that lasts for 3-4 months after flowering.

Bean Quality

Coffee buyers seek beans from ripe cherries. These provide the best quality coffee. Under or over-ripe cherries are too hard and are rejected during processing. Beans are stripped of all outer layers at the plantation and dried down, prior to transporting. 

This early stage processing is undertaken using either a wet, or dry process.

Wet processing involves placing the harvested cherries into a water-filled separating tank. Unripe and partially dried cherries float and are discarded.

Stones and other material sink. Ripe cherries are removed from an appropriate depth near the bottom of the tank. 

The ripe cherries are then passed over a drum, or series of discs, with teeth that remove the pulp. A final fermentation process helps to decompose the film of mucilage around the bean. Then, after washing, the beans are dried. Sun drying encourages photochemical reactions that improve the color and flavor of the beans. Where this is not possible, they are heated.