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Macadamia trees are typically 5 to 18 m tall (15 to 58 ft), with broad crowns almost as wide as they are tall. The leathery, toothed leaves, which occur in whorls of 3 or 4, are oblong to obovate to oblanceolate, 5 to 15 cm (2 to 6 in) long and 2 to 6 cm (0.75 to 2.5 in) wide. The large, branching flower clusters, 8.25 to 25 cm long (3 to 9.75 in), are borne in the axils (where leaf meets stem), and have 100 to 300 small, white, tubular, insect-pollinated flowers. The fruits develop into round nuts, 2 to 4.5 cm (0.75 to 1.5 in) in diameter that have a fleshy green husk that may split open along one suture when mature, revealing a pale brown nut with a hard shell and white, waxy, sweet edible seed.
Macadamia nuts, which are high in fat and protein, may be sold with or more commonly without shells, and are generally eaten roasted and salted as a snack. They are also used in baking, ice cream, and to make candies (including chocolate-coated nuts). They are prepared in some Asian curry dishes.
The USDA estimated that world production of macadamia nuts was 87,754 metric tons in 2001–02. Leading producers were Australia (which accounted for 46% of the total) and the U.S. (which accounted for 28%), followed by South Africa, and Guatemala. Other nations that produced commercial harvests included Costa Rica, Kenya, and China.
Macadamia nuts are also produced the closely related species M. tetraphylla, which is sometimes grown commercially, and M. ternifolia, but the bulk of commercial production is from M. integrifolia. These Macadamia species, as well as M. jensennii, are now considered vulnerable or threatened in their native ranges in Australia due to urban and agricultural land clearing.
(Bailey et al. 1976, Flora of China 2003, Horticulture Australia Limited 2008, McHargue 1996, USDA 2002, van Wyk 2005.)