The coffee plant is a woody shrub native to the understory of the forests of east Africa. The genus responsible for this caffeine-loaded beverage is Coffea, to which taxonomists assign between twenty-five and one hundred distinct species. Some 80 percent of the world's coffee comes from Coffea arabica L., known as arabica coffee on the global market. Most of the remaining world trade features Coffea canephora Pierre ex Froehner, commonly known as robusta coffee. Robustas have about twice the caffeine content found in arabicas.

Coffee belongs to the family Rubiaceae, a commercially important family that provides the drugs quinine (Cinchona spp.) and ipecac (Psychotria ipecacuanha), as well as the sweet-scented ornamental known as Gardenia augusta. Like many woody species growing in a forest setting, coffee has a vertical stem with horizontal branches. The lateral branches become progressively longer the farther away they are from the apical meristem, giving the...