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Almonds, which originated in Western Asia or possibly in the Mediterranean region, are small deciduous trees, up to 9 m (30 feet) tall, similar in appearance to peach trees (Prunus persica). Leaves are alternate and finely-toothed, 7.5–12.5 cm (3–5 inches) long and 2.5–6 cm wide, often with glands on the petiole (leaf stalk). Buds have conduplicate leaves (folded in half within bud), a character useful in distinguishing this from other Prunus species. The bisexual or perfect flowers, which open very early in the spring (and are therefore susceptible to frost damage), are white to pink, single or in pairs, with 5 spreading sepals and 5 or more petals, many stamens, and 1 pistil, which develops into a fuzzy, down-covered drupe (a fleshy fruit with a hard pit or stone). Flowers, and the fruits that develop from them are short-stalked and held close to the branch. Although monoecious (male and female flower parts occur on the same plant), almonds are self-incompatible, so at least two trees must be grown in close proximity for fruit to develop.
The flesh of the almond fruit—which splits open at maturity—is mealy and dry, and not considered edible for humans, although it is sometimes used as livestock feed. However, the stone within may be hard- or soft-shelled, and is generally smooth but with small pits covering the surface, contains the kernel that is widely eaten as a dried “nut.” In addition, kernels of either the sweet or detoxified bitter varieties have numerous uses, including in the candy marzipan, and as flavoring for maraschino cherries, baked goods, extracts, ice cream, amaretto liqueur, and orgeat syrup (used in beverages).
Total global production of almonds in 2010 was 25.3 million metric tons, harvested from 16.6 million hectares. U.S. is the leading producer, responsible for roughly 46% of the commercial harvest, which all comes from California. Spain, Italy, Iran, and Morocco also produce significant amounts.
In addition to being cultivated for their nuts, several varieties of Prunus dulcis, the “flowering almonds,” are cultivated as ornamentals; “flowering almonds” include various double-flowered varieties of P. dulcis, but also includes other species of Prunus, including P. triloba, P. glandulosa, P. japonica, and P. tenella. In addition, two unrelated species are also referred to as almonds: tropical- or Indian-almond (Terminalia catappa) and red-almond (Alphitonia excelsea).
(Bailey et al. 1976, Boriss and Brunke 2005, Everett 1981, Facciola 1998, FAOSTAT 2012, Wiersema & León 1999)