What do you think of this fact?
At the supermarket, peanuts sit right next to cashews, almonds and walnuts. They’re called nuts, they crack like nuts, they taste nutty. Botanically, though, the verdict is clear: the peanut isn’t a nut. It’s a legume.
The bean family
The peanut (Arachis hypogaea) belongs to the legume family, Fabaceae. That family also includes peas, beans and lentils. What you’re cracking open is basically a pod with seeds inside, like a pea pod, just firmer and drier.
A true nut in the botanical sense is a fruit with a hard, woody shell that doesn’t split open on its own, like a hazelnut. The peanut doesn’t fit, even if everyday language treats it as one. It originally comes from South America, and today it’s grown almost everywhere in the world.
A plant that buries itself
Now it gets properly weird. Most plants hang their fruit from branches or stems. The peanut does the opposite. It flowers above ground with small blossoms. After fertilization, the stalk below the flower grows downward, forming what’s called a peg. The peg pushes into the soil, and only there does the pod with the seeds develop.
Botanists call this geocarpy: fruit that ripens underground. Hence the name groundnut. The plant literally buries its own offspring. According to NC State Extension, the first flowers appear about 40 days after planting, and the pods are ripe after roughly 120 to 150 days.
The peanut has plenty of nicknames in English, including “goober”, “groundnut” and “monkey nut”.
Nut by name, bean at heart
The peanut gets called a nut because of how it’s used in the kitchen. There, what counts is how something tastes and gets used, not where it sits on the plant family tree. The same logic is why tomatoes count as vegetables in cooking.
So your peanut butter is technically a bean spread. Still delicious.