While there are many species of wild coffee, the two dominant commercial species grown worldwide are varieties of Coffea arabica (Arabicas) and Coffea canephora (Robustas). These are largely grown in plantations or forested areas adapted for farming.
The coffee bean itself is in fact a seed. Once planted in nurseries, seedlings will take between 3 to 4 years to mature and begin bearing fruit. It can however take around a decade for a tree to fully become established. Once mature, trees typically only bear one harvest a year.
Ideal average temperatures range between 15 to 24ºC for Arabica coffee and 24 to 30ºC for Robusta, which can flourish in hotter, harsher conditions. Coffee needs an annual rainfall of 1,500 to 3,000 mm, with Arabica needing less than other species. Whereas Robusta coffee can be grown between sea-level and about 800 metres, Arabica does best at higher altitudes and is often grown in hilly areas.
The average Arabica plant is a large bush with dark-green oval leaves. The fruits, or cherries, are rounded and mature in 7 to 9 months; they usually contain two flat seeds, the coffee beans. When only one bean develops it is called a peaberry.
Robusta is a robust shrub or small tree that grows up to 10 metres high. The fruits are rounded and take up to 11 months to mature; the seeds are oval in shape and smaller than Arabica seeds.
A successful coffee crop requires careful management. This involves trimming and pruning trees, to help them establish themselves and stimulate fruiting, but also responding to potential threats to a harvest.
Coffee can be susceptible to pests, some of which appear to be becoming more prevalent as a result of climate change and rising temperatures. The coffee borer in particular (genus Coffea) is said to now be present in almost all coffee-growing regions worldwide. Rising temperatures have also made coffee more susceptible to fungicidal infections, otherwise known as ‘rust’.
Farmers can tackle both of the aforementioned threats to crops through appropriate use of pesticides and fungicides, as well as more natural techniques including shade-grown coffee or promoting local biodiversity such as birds, which may naturally prey on pests.
Coffee has historically been grown in the shade of other trees, often growing naturally in wild forest settings. Some agricultural techniques which somewhat replicate these settings. This includes planting coffee alongside trees (agroforestry) or crops which may provide financial value because of their fruit, leaves, or timber. These methods can potentially help farmers diversify their income as well as playing a restorative role for soil health, carbon sequestration, water balance, and biodiversity.
Coffee cherries will typically turn red when ripe, signalling to farmers that they are ready for harvest.
As coffee is often grown in mountainous areas, widespread use of mechanical harvesters is not possible and the ripe coffee cherries are usually picked by hand. The main exception is Brazil, where the relatively flat landscape and immense size of the coffee fields allow for machinery use.
Coffee trees yield an average of 2 to 4 kilos of cherries and a good picker can harvest 45 to 90 kilos of coffee cherry per day; this will produce nine to 18 kilos of coffee beans.
Coffee is harvested in one of two ways:
- Strip picked – all the cherries are stripped off of the branch at one time, either by machine or by hand
- Selectively picked – only the ripe cherries are harvested and they are picked by hand
Pickers check the trees every 8 to 10 days and individually pick only the fully ripe cherries. This method is labour intensive and more costly. Selective picking is primarily used for the finer Arabica beans.
Following harvesting, the coffee cherries then undergo a range of post-harvest steps, which traditionally differ between Arabica and Robusta species, to result in green coffee beans.