Are Peanuts Nuts or Peas? (Why Are Peanuts Not Nuts?)

The question of whether peanuts are nuts or peas is a common point of confusion, largely stemming from their culinary use and name. Botanically speaking, peanuts (Arachis hypogaea) are not true nuts; they are legumes, belonging to the Fabaceae family, which is also known as the pea or bean family. This makes them relatives of foods like lentils, chickpeas, and soybeans.

Understanding why peanuts are classified as legumes rather than true nuts requires a look at botanical definitions. A true nut, in botanical terms, is a hard-shelled pod that contains both the fruit and seed of the plant, where the fruit does not open to release the seed. Examples of true nuts include acorns, chestnuts, and hazelnuts. The key characteristic is that the ovary wall becomes hard at maturity.

Peanuts, on the other hand, grow underground (which is why they are also called groundnuts), and their seeds (the peanuts themselves) are contained within a pod that develops from the ovary of a flower. The peanut plant flowers above ground, but after pollination, the flower stalk elongates, bends towards the earth, and pushes the fertilized ovary (called a peg) into the soil. The peanut pod then develops underground. This method of fruit development is quite unique and is known as geocarpy. The pod of a peanut is the mature ovary, containing multiple seeds (the "nuts" we eat). Legumes are characterized by fruits that are typically pods which may split open along two seams to release their seeds. While peanut pods don't always split open in the same way as some other beans, their overall structure and plant family firmly place them in the legume category.

The confusion arises because, in culinary contexts and everyday language, "nut" is used much more broadly to refer to any large, oily kernel found within a shell and used in food. This culinary definition includes many true nuts but also drupes (like almonds, walnuts, pecans, and cashews – where the edible part is the seed from inside a fruit) and legumes like peanuts. Peanuts share many culinary characteristics with true nuts: they are often roasted, salted, used in snacks and confections, and made into butter. Their nutritional profile, being rich in protein and fats, also mirrors that of many true nuts.

So, why are peanuts not nuts? It's because their botanical structure and origin define them as a type of pea or bean – a legume. They grow in a pod, they are the seeds of a plant in the Fabaceae family, and their development process is distinct from that of true nuts. While almonds, walnuts, and cashews are also not true nuts (they are seeds of drupes), peanuts are even further removed, belonging to an entirely different plant family group.

This distinction is particularly important for individuals with allergies. While someone might be allergic to peanuts (a legume), they may not necessarily be allergic to tree nuts (which include true nuts and drupes like almonds, walnuts, cashews). However, the proteins in peanuts can be very allergenic for some individuals, leading to severe reactions. The term "nut" in "peanut" is a common misnomer that has persisted due to culinary similarities rather than botanical accuracy. Therefore, it's crucial to remember that despite their name and common usage, peanuts are botanically legumes, closely related to peas and beans.