Though coffee (coffea) belongs to a genus of 10 species of flowering plants of the family Rubiaceae, only 2 species are currently of economic value:

  • Coffea arabica, referred to in trade as arabica and accounting for less than 70% of world production
  • Coffea robusta, called robusta in the trade and making up over 30% of world production.

Arabica coffee is considered more suitable for drinking than robusta coffee; robusta tends to be bitter and have fewer flavors than arabica.  For this reason, about seven- tenths of coffee cultivated worldwide is arabica. However, robusta is less susceptible to disease than arabica and can be cultivated in environments where arabica will not thrive.  Robusta coffee also contains about 40–50%more caffeine   than arabica.  For this reason, robusta is used (1) as an inexpensive substitute for arabica in many commercial coffee blends,   and (2) as the main ingredient for instant coffee.   Good quality robustas are used in some espresso blends to provide a better foam head and to lower the ingredient cost.  

Arabica and robusta are both tree crops which produce yields 3 to 4 years after planting and have an economic life of between 20 and 30 years, depending on local conditions and husbandry. Although both thrive only in the tropical and subtropical belt, each requires different growing conditions.  Arabica prefers a climate tempered by altitude with temperatures of 18-240C and with contrasting seasons. Arabica grows best between 1,000 and 2000 meters.  Robusta, on the other hand, grows best under warm equatorial conditions with annual temperatures averaging 24-260C and less contrasting dry and rainy seasons.

The effects of temperature and altitude can be mitigated by the use of shade trees, which reduce light intensity and help to retain soil moisture.