Coffea arabica L. (Rubiaceae)



Rows of coffee plants on a commercial coffee farm in Brazil (S.A.Harris). Vegetative shoot of Coffea arabica. Flower of Coffea arabica.

Caffeine is the world's most widely used legal stimulant. Annually, we consume the equivalent of 100,000 tonnes of pure caffeine from botanical sources such as coffee, tea and chocolate. Until the sixteenth century, and the arrival of chocolate, most Europeans never consumed caffeine. The first English coffee house was established in Oxford in 1650, and these establishments soon spread, becoming associated with the socio-political and intellectual revolutions of the seventeenth and eighteenth centuries.

Today, caffeine is a national addiction and most cities boast at least one coffee shop. The caffeine content of a cup of coffee ranges between 300 and 2200 mg per litre, depending on the source and method of coffee preparation. For plants, caffeine and its derivatives are biochemical weapons; they help to protect plants from disease and insect damage.

The approximately 100 Coffea species are naturally restricted to the Old World, and distributed through tropical Africa to the Mascarenes. Coffee is commercially extracted from the roasted seeds (beans) of three Coffea species. The most important is Coffea arabica, an evergreen shrub with shiny green leaves, fragrant white flowers and crimson, cherry-sized fruits, and a natural distribution in the mountains of southwest Ethiopia.

The legend of the discovery of coffee's peculiar properties is one of giddy Ethiopian goats being observed after eating the shrub's berries, with humans mimicking the goats' behaviour. By 1000 AD, coffee was being cultivated by Arabs on the Red Sea coast.

In 1718, the horticultural enthusiast Richard Bradley was enthusing about the success of coffee cultivation in Holland and her colonies: 'In the Amsterdam Garden, ... I have seen some of these Trees near eighteen Foot high, so full of Berries, that several Pound Weight of Fruit was gather'd off of two Trees only.' Bradley was convinced the British should follow the Dutch example 'in the South Parts of Carolina, ... [it] would be well worth our Trial, if that Country remains in our Hands'. However, coffee never became a significant crop for the early American colonists. Bradley's thoughts were reflected by those of Linnaeus and the Swedish government when a doomed policy of economic self-sufficiency was promoted.

Today, most of the world's coffee beans are produced in the South America. One of the periods of Brazilian economic expansion in the nineteenth century became known as the coffee cycle, and contributed to the destruction of one of the world's biodiversity hotspots, the Atlantic forest.

Further reading

Prendergrast M 2010. Uncommon grounds: the history of coffee and how it transformed our world. Basic Books.

Weinberg BA, Bealer BK 2002. The world of caffeine. The science and culture of the world's most popular drug. Routledge.

Stephen Harris

BBC Radio Oxford clip about this week's plant