Many foods called “nuts” are not botanically classified as such. The distinction between culinary and botanical definitions often leads to confusion. Understanding the precise botanical classifications of seeds and fruits clarifies why many familiar “nuts” are something else entirely. This article explains their scientific definitions.
The Botanical Definition of a Seed
A seed is a plant’s reproductive unit, originating from a mature ovule after fertilization. It contains an embryo, a miniature plant, surrounded by stored food reserves for initial growth. A protective seed coat encloses these components, guarding them against environmental stressors. Its primary purpose is to facilitate reproduction and dispersal, enabling germination when conditions are favorable.
What Constitutes a True Nut?
A true nut is a specific type of fruit, botanically classified as a simple dry fruit. It has a hard, woody shell, or pericarp, surrounding a single seed. True nuts are indehiscent, meaning the pericarp does not naturally open at maturity to release the seed. Examples include acorns (the fruits of oak trees), hazelnuts, and chestnuts.
Common “Nuts”: Unveiling Their Botanical Identity
Many items commonly called “nuts” are not true nuts botanically, nor are they always simple seeds. Their classifications often reveal them to be parts of other fruit types.
Drupe Seeds (Almonds, Walnuts, Pecans, Pistachios)
Almonds, walnuts, pecans, and pistachios are botanically classified as the seeds of drupes. A drupe is a fleshy fruit with a hard inner layer, or “pit,” that encloses the seed, similar to peaches or cherries.
Cashews
Cashews are also drupe seeds, but they develop uniquely, hanging from a fleshy structure called a cashew apple, which is an accessory fruit. The edible portion of the cashew is the seed contained within a kidney-shaped drupe that forms below this apple.
Peanuts
Peanuts are not nuts at all, but legumes. They are botanically related to beans and peas, growing in pods underground.
Brazil Nuts
Brazil nuts are true seeds, though they are often mistaken for nuts. These large seeds are found within a substantial, woody fruit pod produced by the Brazil nut tree.
Pine Nuts
Pine nuts are also true seeds, harvested from the cones of various pine tree species, where the seeds are not enclosed within an ovary that develops into a fruit, characteristic of gymnosperms.