Everyday
Is a peanut a nut?
The short answer
No. A peanut is a legume, a relative of peas, beans and lentils, and it grows in a pod underground. After the plant flowers above ground, the fertilised flower sends a stalk called a peg down into the soil, and the peanut develops there in the dark.
Nuts, in the botanical sense, grow on trees: walnuts, hazelnuts, chestnuts. Peanuts grow on a low, bushy plant about knee high, and the plant is a legume, which means it fixes nitrogen in its roots and fills its pods with seeds exactly the way a pea plant does. Split a peanut and you will find two halves and a tiny embryo, just like a bean.
The growing method is the strange part. Peanut plants flower in the open air like anything else, but once a flower has been pollinated, its stalk bends down and keeps growing until it pushes into the soil. Only then does the pod begin to form, a few centimetres underground. Botanists call it geocarpy, and if the peg fails to reach the ground, no peanut grows.
Harvesting means pulling the whole plant up like a carrot and finding the pods dangling from its roots. So the peanut butter in your cupboard is made of legume seeds that were buried alive by their own flowers. The name was never going to be fixed after that.
Sources
- Arachis hypogaea (Peanut)North Carolina State University Extension
- Peanuts in the GardenUtah State University Extension