The cashew is in the family Anacardiaceae. Its English name derives from the Portuguese name for the fruit of the cashew tree, caju, which in turn derives from the indigenous Tupi name, acajú. It is now widely grown in tropical climates for its cashew nuts (see below) and cashew apples.
The name Anacardium refers to the shape of the fruit, which looks like an inverted heart (ana means "upwards" and -cardium means "heart"). In the indigenous language akaju means "yellow head".
Habitat and growth
The tree is small and evergreen, growing to 10-12m (~32 ft) tall, with a short, often irregularly shaped trunk. The leaves are spirally arranged, leathery textured, elliptic to obovate, 4 to 22 cm long and 2 to 15 cm broad, with a smooth margin. The flowers are produced in a panicle or corymb up to 26 cm long, each flower small, pale green at first then turning reddish, with five slender, acute petals 7 to 15 mm long.
What appears to be the fruit of the cashew tree is an oval or pear-shaped accessory fruit (sometimes called a pseudocarp or false fruit) that develops from 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 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.
The true fruit of the cashew tree is a kidney or boxing-glove shaped drupe that grows at the end of the accessory fruit. The drupe develops first on the tree, and then the peduncle expands into the cashew apple. Within the true fruit is a single seed, the cashew nut. Although a nut in the culinary sense, in the botanical sense the nut of the cashew is a seed. The seed is surrounded by a double shell containing an allergenic phenolic resin, anacardic acid, a potent skin irritant chemically related to the more well known allergenic oil urushiol which is also a toxin found in the related poison ivy. Some people are allergic to cashew nuts, but cashews are a less frequent allergen than nuts or peanuts.
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