The three main varieties of cacao beans used in chocolate are criollo, forastero, and trinitario. Representing only 5% of all cacao beans grown, criollo is the rarest and most expensive cacao on the market, and is native to Central America, the Caribbean islands and the norther tier of the South American states. Criollos are particularly difficult to grow, as they are vulnerable to a variety of environmental threats and produce low yields of cacao per tree. The flavor of criollo is described as delicate yet complex, low in classic chocolate flavor but rich in "secondary" notes of long duration. Criollo cacao is known as the "King of Chocolate."
The most commonly grown bean is forastero, a large group of wild and cultivated cacaos, mostly likely native to the Amazon basin. The African cacao crop is entirely of the forastero variety. They are significantly hardier and of higher yield than criollo. The source of most chocolate marketed, forastero cacaos are typically strong in classic "chocolate" flavor, but have a short duration and are unsupported by secondary flavors, producing a "quite bland" chocolate.
Trinitario is a natural hybrid of criollo and forastero. Trinitario originated in Trinidad after an introduction of forastero to the local criollo crop. Nearly all cacao produced over the past five decades is of the forastero or lower-grade trinitario varieties.