Description of a Cashew Nut Tree

Overview

The cashew nut tree (Anacardium occidentale) is close relative of many other famous or infamous plants: mango, sumac, pistachio and poison ivy. A member of the cashew family, anacardiaceae, the cashew nut tree is native to tropical Central and South America. It is not hardy to winter frosts and thus is grown in the U.S. only in U.S. Department of Agriculture hardiness zones 10 and warmer.

Growth Habitat

Cashew nut trees grow in tropical areas that are arid and thus grow slowly. The plant reaches a mature height of 30 to 40 feet and a canopy spread of 50 to 75 feet. Margaret Barwick describes the tree in "Tropical and Subtropical Trees" as "awkward, knobby" trees with sprawling, leaning trunks and contorted branches. It grows best in fertile, dry soils that, when wetted by seasonal rains, retain the moisture for an extended period.

Foliage

Excessive drought causes the leaves of cashew nut trees to partially drop away during the dry season in the tropics. Each leaf is dull green, although with a satiny finish, and is a wide oval. The leaves are stiff, leathery and roughtly textured. The midvein is contrastingly yellow.

Flowering Characteristics

From the tips of branches, held stiffly and visibly above the leaves are panicles of tiny flowers that usually occur in the tropical dry season. The tiny yellowish-white flowers are five-petaled and fragrant and age to soft brick red. Insects pollinate the flowers, which then over the course of two to three months yield fruits.

Fruit Development

There is a dual fruit and nut development on cashew nut trees. Pollinated flowers produce a receptacle, which is a botanical term used for a swollen flower stem. This receptable is often called the "apple," which matures to a shape like a non-curvaceous pear colored either golden yellow or red depending on the tree. This fruit-like receptacle is spongy and has a resinous flesh that is edible but acidic and bitter. At the bottom of the "apple" is the true fruit---a fat, kidney-shaped shell that is black because of it being ridden with a black oil (known commercially as cardol oil). The embryo resides inside the hard shell or kernel. This exposed embryo is the "nut" we eat with that characteristic curving kidney shape and light color.

Hazards

All members of the anacardiaceae, including the cashew nut tree, contain a sap that irritates the skin. Whether you touch the leaves, the sap of a broken twig, the fruitlike receptacle or the unroasted kernel of the nut fruit, chances are the contact by bare skin will result in a burning rash. In fact, the kernel of the cashew nut is oily and must be roasted before being eaten to remove any toxicity before it can be enjoyed for a snack.