The Cashew (Anacardium occidentale) is a tree in the flowering plant family Anacardiaceae. The plant is native to northeastern Brazil, where it is called by its Portuguese name Caju (the fruit) or Cajueiro (the tree). It is now widely grown in tropical climates for its cashew “nuts” (see below) and cashew apples.
It is a small evergreen tree growing to 10-12 m tall, with a short, often irregularly-shaped trunk. The leaves are spirally arranged, leathery textured, elliptic to obovate, 4-22 cm long and 2-15 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 7-15 mm long.
What appears on the tree to be the fruit of the cashew tree is an oval to pear-shaped accessory fruit 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.
The true fruit of the cashew tree is a kidney or boxing-glove shaped drupe that grows at the end of the pseudofruit. Actually, the drupe develops first on the tree, and then the peduncle expands into the pseudofruit. Within the true fruit is a single seed, the cashew nut. Although a nut in the culinary sense, in the botanical sense the fruit of the cashew is a seed. However, the true fruit is classified as a nut by some botanists. The seed is surrounded by a double shell containing a caustic phenolic resin, urushiol, a potent skin irritant toxin (also found in the related poison-ivy). Some people are allergic to cashews, but cashews are a less frequent allergen than some other nuts