The cashew tree (Anacardium occidentale) is a tropical evergreen tree that produces the cashew nut and the cashew apple. It can grow as high as 14 m (46 ft), but the dwarf cashew, growing up to 6 m (20 ft), has proved more profitable, with earlier maturity and higher yields.
The cashew nut, often simply called a cashew, is widely consumed. It is eaten on its own, used in recipes, or processed into cashew cheese or cashew butter. The shell of the cashew seed yields derivatives that can be used in many applications from lubricants to paints. The cashew apple is a light reddish to yellow fruit, whose pulp can be processed into a sweet, astringent fruit drink or distilled into liquor.
Its English name derives from the Portuguese name for the fruit of the cashew tree caju (Portuguese pronunciation: [kaˈʒu]), which itself is derived from the Tupian word acajú, literally meaning “nut that produces itself”. The generic name Anacardium, originally from the Greek, refers to the unusual location of the seed outside the core or heart of the fruit (ana- means “again” or “backward” and -cardium means “heart”). A mid-seventeenth century ethnographic painting by Albert Eckhout, who accompanied Dutch governor-general Johan Maurits, shows a woman under a fruiting cashew tree.
The cashew tree is large and evergreen, growing to 14 m (46 ft) tall, with a short, often irregularly shaped trunk. The leaves are spirally arranged, leathery textured, elliptic to obovate, 4–22 cm (1.6–8.7 in) long and 2–15 cm (0.79–5.91 in) broad, with smooth margins. The flowers are produced in a panicle or corymb up to 26 cm (10 in) long; each flower is small, pale green at first, then turning reddish, with five slender, acute petals 7–15 mm (0.28–0.59 in) long. The largest cashew tree in the world covers an area around 7,500 m2 (81,000 sq ft); it is located in Natal, Rio Grande do Norte, Brazil.
The fruit of the cashew tree is an accessory fruit (sometimes called a pseudocarp or false fruit). What appears to be the fruit is an oval or pear-shaped structure, a hypocarpium, that develops from the pedicel and the receptacle of the cashew flower. Called the cashew apple, better known in Central America as marañón, it ripens into a yellow and/or red structure about 5–11 cm (2.0–4.3 in) long. It is edible, and has a strong “sweet” smell and a sweet taste. The pulp of the cashew apple is very juicy, but the skin is fragile, making it unsuitable for transport. In Latin America, a fruit drink is made from the cashew apple pulp which has a very refreshing taste and tropical flavor that can be described as having notes of mango, raw green pepper, and just a little hint of grapefruit-like citrus.
The true fruit of the cashew tree is a kidney or boxing-glove shaped drupe that grows at the end of the cashew apple. The drupe develops first on the tree, and then the pedicel expands to become the cashew apple. Within the true fruit is a single seed, which is often considered a nut, in the culinary sense. The seed is surrounded by a double shell containing an allergenic phenolic resin, anacardic acid, a potent skin irritant chemically related to the better-known allergenic oil urushiol which is also a toxin found in the related poison ivy. Properly roasting cashews destroys the toxin, but it must be done outdoors as the smoke (not unlike that from burning poison ivy) contains urushiol droplets which can cause severe, sometimes life-threatening, reactions by irritating the lungs. People who are allergic to cashew (or poison ivy) urushiols may cross-react to mango or pistachio which are also in the Anacardiaceae family. Some people are allergic to cashews, but cashews are a less frequent allergen than tree nuts or peanuts.