What is a Cashew Nut?

What is a Cashew? Nut, Fruit, or Something Else? 

Cashew nuts (Photo: Wiki Commons, see attribution)

Unraveling the Mystery of the Cashew Nut

Most people know about the fact that a tomato is really a fruit and not a vegetable. In your science class you probably learned that fruits come from the ovaries of plants and bear seeds, while vegetables are all the other parts of plants (stems, roots, leaves, etc.). There are foods that continually  get mis-categorized, and that's especially true of nuts. In this  post I will explain what a cashew nut is, and why it's not truly a nut.

I love cashews and cashew butter, but I always wondered what exactly a cashew nut looked like. Sure, they come in bags with almonds, walnuts, peanuts, and other mixed nuts. They're even sold in the nut aisle, but when I did a little digging I found out that the cashew is not truly a nut.

WHAT IS A NUT? 

Here are the characteristics of a nut as they are described by botanists: 

  • Inedible hard outer shell.
  • Inner edible seed
  • The outer hard shell does not break open when ripe { indehisent (in-dee-hiss-ant)}
  • Examples of seeds that are nuts: acorns, hazelnuts, and chestnuts

The term nut is confusing because cooks and laymen have often use the term "nut" to refer to any edible kernel inside a hard shell, such as walnuts, almonds, and pecans. These are not really, botanically speaking, nuts. This is because they are technically DRUPES or stone fruits. Yes,  drupes are seeds, just like nuts, but they come from the ovary wall of a flower and are surrounded by fleshy goodness.  Examples of this would be a peach, the fleshy hull of a walnut, or the fleshy covering of a pecan. Yes, they also have a hard outer covering that requires cracking, but there's an extra step to get get to the stone fruit of drupes, namely removing or fermenting the outer fleshy bits covering the inner seed. Other famous examples of drupes include coffee, mango, and olives.

CASHEW "NUTS"

All of this brings us to the cashew nut. The word cashew comes from the derivative of Portuguese for the cashew tree caju, and the South American term acaju. This is also the shortened French word acajou. All of these are the terms for the actual tree which produces the nut. You see, a cashew is really the seed of the cashew tree (Anacardium occidentale), which is an evergreen tree that grows in tropical and humid environments. It's native to Brazil, but has been exported as a crop tree to Vietnam, India, and Africa. The tree can grow up to 40 feet high, though there are cultivar shrubs that are smaller and easier to harvest.

Cashew plant botanic illustration (Image: Wiki Commons, see attribution)

Cashew tree leaves and fruit (Photo: Pixaby, see attribution)

Cashew nuts are really the seeds of the cashew apple, which is the fruit of the cashew tree. Cashew apples are red or yellow, very tart, and often used in making alcohol or deserts. As the fruit of the cashew apple declines it produces a drupe or seed at its tip. The Latin name of the cashew tree "Anacardium" is derived from the terms ana or "above" and kardia or "heart" because the seed sits outside the heart or tip of the fruit.  Kind of odd looking and definitely different from what we'd expect of a peach or something similar.

Cashew fruits (Photo: Pixino, free use, see attribution)

The true fruit of the cashew tree is the cashew nut. As mentioned earlier, the cashew nut is a drupe which is a kidney shaped and has a  hard casing. The drupe develops at the end of the cashew apple.

Cashew fruit (Photo: Wiki Commons, see attribution)

The casing of the nut itself is challenging. It has oils in it that are like that of poison ivy or sumac (called urushiol). It can cause intense skin itching, blistering, and irritation. However, the shell can also be ground and used as a lubricant, for paints, or even rubber compounds. There is a resiny oil in the shell that  is called cashew nut shell liquid oil (CNSL), you can read all about the uses here. It's even sold in drums or barrels for industrial purposes.

Young cashew nuts (Image: Wiki Commons, see attribution)

The cashew seed is used in all sorts of cooking, especially in countries where it is native. Culinary uses include curries, pastes, and marzipan and you can find recipes for anything from vanilla cashew ice cream to salsa.  ( Click here for examples.)   Most allergies to eating cashews are from the proteins in the nuts, this is because the itchy outer shell is removed, but cashews are often more "safe" than other edible seeds for those with food allergies.

The cashew is also not a legume, from the roots of a plant, like peanuts. Truly cashew "nuts" are very unique. They're time-consuming to collect and harvest, can break you out in hives if you touch the shells, and only one grows per drupe so you need a lot of trees and fruits. Watch this video to learn more.  Once you know how cashews are grown and produced, it sort of makes up for their higher prices, because even if they are a little unusual, even mis-identified, they're still yummy!