The question of how many different kinds of nuts exist is complicated because the term “nut” is used loosely in everyday language compared to its precise scientific definition. These seed-bearing foods are valued for their dense nutritional content, healthy fats, and distinct flavors. Determining the true count requires navigating the differences between what a botanist calls a nut and what a chef or consumer calls one. This distinction is fundamental to understanding the variety of items we commonly group under this single name.
The Conflict in Definition: Culinary Versus Botanical
The term “nut” has two distinct meanings that are strictly separate in science. Botanically, a true nut is defined as a simple, dry fruit that contains only one seed and does not open naturally upon maturity. This fruit develops an extremely hard, woody outer wall, or pericarp, which encases the single seed.
In contrast, the culinary definition is much broader. For general consumption, a nut is simply any large, oily kernel or edible seed protected by a shell or husk. This practical definition encompasses a vast array of plant parts, explaining why many popular items labeled as nuts are not classified as such by botanists.
Families of True Botanical Nuts
When limiting the scope to the botanical definition, the number of distinct plant families that produce true nuts is quite small. True nuts are primarily produced by certain plant families within the order Fagales, satisfying the criteria of an indehiscent, hard-shelled fruit.
The family Fagaceae, which includes the oaks and chestnuts, is a major source. Acorns are classic examples. Chestnuts (Castanea genus) also fit the criteria, though they are unique for having a much higher starch content than fat content.
The Betulaceae family contributes the hazelnut (filbert). Hazelnuts adhere to the standard of a dry, single-seeded fruit that remains closed. The classification of fruits in the Juglandaceae family (walnuts and pecans) is more complex. They are sometimes categorized as drupaceous nuts or nut-like drupes because their structure shares characteristics with both true nuts and drupes.
Edible Seeds Commonly Misidentified as Nuts
The vast majority of items commonly consumed as nuts are actually seeds or other types of fruit. A large category of these misidentified items are the seeds of drupes, which are fleshy fruits like peaches and cherries. Drupes feature an outer fleshy layer and a hard middle layer (the endocarp) that forms the pit or stone, containing the seed inside.
Botanically, the following are seeds found within the pits of drupes, not true nuts:
- Almonds
- Cashews
- Macadamias
- Pecans
- Pistachios
- Walnuts
The almond, for example, is the seed inside the hard shell (the pit of the fruit). The cashew is the seed that grows beneath the cashew apple.
Another significant classification is the legume, a dried fruit that splits open along two seams. Peanuts are the seeds of a legume plant and grow in pods underground, placing them in the Fabaceae family alongside lentils and chickpeas. Pine nuts are the edible seeds harvested from the cones of certain pine trees. These seeds are part of the gymnosperm group, demonstrating the structural diversity of foods referred to as nuts.