Conservatory Chronicles: The Cashew Nut - Do You Really Know It?

Visit the conservatory at Matthaei Botanical Gardens this winter and you’ll see a new addition to the tropical house—a cashew tree. The cashew is native to South America, primarily Brazil, but is now widely grown in tropical climates around the world. Interestingly, cashew production has traveled to the Old World to places like Africa and South Asia.

The cashew tree is botanically known as Anacardium occidentale and produces a nut (actually a seed). The cashew belongs to the plant family Anacardiaceae, the same family to which poison ivy (Toxicodendron radicans) belongs. The cashew tree contains substances that are similar to poison ivy in its leaves, sap, and especially in the tissues surrounding the cashew seed, and these substances can cause considerable skin irritation. Humans can eat the cashew only after the skin and oils surrounding the nut have been removed and the nut roasted.

The cashew tree in its pot in the conservatory at
Matthaei Botanical Gardens

In Brazil another part of the cashew plant is eaten, the “cashew apple.” This is the swollen stem just above the cashew seed. When ripe it’s the size and shape of a small pear that might come in shades of yellow, orange, or red. The cashew apple can be eaten fresh or processed into a pulpy drink or even an apple butter-like spread. The cashew apple is extremely perishable and rarely seen outside the tropics.

Botanically the cashew seed is not classified as a nut. In fact, a true nut is a single seed that is indehiscent, that is, no seam to split open. For example, acorns and filberts are true nuts. Other seeds commonly called nuts that are not true nuts botanically are peanuts, walnuts, pistachios, almonds, and Brazil nuts, to name a few. These are called nuts because of their culinary use.

A picture of the cashew apple. Photo courtesy of Rancho Vignola .

Finally, you may wonder why our cashew tree is in a large pot, instead of planted directly in the ground. Potting the plant helps control its size, since cashew trees can reach 40 feet tall and wider still. Restricting the root zone keeps the tree small yet still able to bear fruit.

With thanks to Rancho Vignola on Flickr  for the cashew apple shot.