Oncobasidium theobromae Theobroma cacao ; Theobroma cacao also cacao tree and cocoa tree, is a small (4–8 m or 15–26 ft tall) evergreen tree in the family Sterculiaceae (alternatively Malvaceae), native to the deep tropical region of the Americas. Its seeds are used to make cocoa powder and chocolate. There are two prominent competing hypotheses about the origins of the domestication of the originally wild Theobroma cacao tree. One is that wild examples were originally distributed from southeastern Mexico to the Amazon basin, with domestication taking place both in the Lacandon area of Mexico and in lowland South America. But recent studies of Theobroma cacao genetics seem to show that the plant originated in the Amazon and was distributed by humans throughout Central America and Mesoamerica.
The tree is today found growing wild in the low foothills of the Andes at elevations of around 200–400 m (650–1300 ft) in the Amazon and Orinoco river basins. It requires a humid climate with regular rainfall and good soil. It is an understory tree, growing best with some overhead shade. The leaves are alternate, entire, unlobed, 10–40 cm (4–16 in) long and 5–20 cm (2–8 in) broad. Poisonous and inedible, they are filled with a creamy, milky liquid and taste spicy and unpleasant.
The flowers are produced in clusters directly on the trunk and older branches; they are small, 1–2 cm (1/2–1 in) diameter, with pink calyx. While many of the world's flowers are pollinated by bees (Hymenoptera) or butterflies/moths (Lepidoptera), cacao flowers are pollinated by tiny flies, Forcipomyia midges in the order Diptera. The fruit, called a cacao pod, is ovoid, 15–30 cm (6–12 in) long and 8–10 cm (3–4 in) wide, ripening yellow to orange, and weighs about 500 g (1 lb) when ripe. The pod contains 20 to 60 seeds, usually called "beans", embedded in a white pulp. Each seed contains a significant amount of fat (40–50%) as cocoa butter. Their most noted active constituent is theobromine, a compound similar to caffeine.
The scientific name Theobroma means "food of the gods". The word cacao itself derives from the Nahuatl (Aztec language) word cacahuatl, learned at the time of the conquest when it was first encountered by the Spanish. Similar words for the plant and its by-products are attested in a number of other indigenous Mesoamerican languages.