Arabica coffee is only found growing in its indigenous environment at elevations between 1000 and 2000 metres above sea level. (Schmitt, Christine B., 2006) But you will find coffee plantations at elevations ranging from sea level to as high as 2800 metres. The reason for this limited growing range is the species’ relatively low tolerance to frost — sustained temperatures below 4° C will kill the plant. Arabica’s susceptibility to fungal pathogens also limits its success at low altitudes, where such microorganisms are more likely to thrive.
The growing altitude correlates directly to the plant’s ideal ‘temperature band’. In other words, successfully growing arabica coffee depends on a delicate balance between altitude and latitude. For optimal cellular respiration to produce good yields and great flavour, agronomist Leonardo Henao states that a daytime temperature between 17 and 23° C is the key factor in optimising coffee metabolism and the storage of sugars in the seed. (You can listen to a discussion of this topic in this podcast by Tom Owen.) Outside of this temperature band, the coffee plant is effectively asleep. In the warm, tropical belt, this balance is most often achieved at elevations of between 1000 and 2000 metres above sea level.
Arabica coffee can grow outside the tropics, but in these instances the suitable terroir tends to be found at lower latitudes. An example of this occurs around Byron Bay in Australia, where a subtropical rainforest climate in close proximity to the sea helps to prevent frost. As you may recall from high school geography class, ocean temperatures are far slower to change than the temperatures on land. This is because the specific heat of water is much higher than earth and stone; it takes about five times as much energy from the sun to heat 1 kilogram of water by 1 degree Celsius than it does to heat 1 kg of rock by 1 degree.
An Interview with Willem Boot
Willem Boot is a pioneer of high-altitude farming of the geisha coffee cultivar around Boquete in Panama.