Coffea arabica grows wild in the mountain rain forests of Ethiopia, where it inhabits the middle tier of the forest, halfway between the brushy ground cover and the taller trees. It grows best wherever similar conditions prevail: no frost, but no hot extremes; fertile, well-watered but well-drained soil (soil of volcanic origin seems best). Heavy rainfall can cause the trees to produce too much too fast and exhaust themselves; inadequate rain prevents the trees from flowering or bearing fruit. The tree requires some but not too much direct sunlight; two hours a day seems ideal. The lacy leaves of the upper levels of the rain forest originally shaded the coffee tree.
In many parts of the world, including Central America, Mexico, Colombia, Ethiopia, and other regions, arabica coffee is traditionally grown in shade, which can range from dense thickets of native plants to careful, uniform plantings of imported shade trees. In other parts of the world — Hawaii, the Mandheling region of Sumatra, the Blue Mountain region of Jamaica, and many other places — coffee is not grown in shade because the weather is too rainy and wet and the trees need all the sun they can get. In other places — Yemen, Brazil — coffee is traditionally grown in sun.
The tendency of growers in regions where shade growing is traditional to replace shade-grown coffee groves with new hybrid trees that grow well in sun and bear quickly and heavily is controversial, since these new fields of sun-grown coffee reduce diversity and require more artificial chemical inputs than shade-grown trees.
