The classification of nuts, fruits, and vegetables often causes confusion, as culinary uses differ from precise botanical definitions. Many items commonly called “nuts” are not true nuts botanically. This distinction highlights the difference between how we categorize foods for cooking and how plant scientists classify them based on their biological structures and development. Understanding these botanical truths reveals the surprising identities of many familiar foods.
Understanding Botanical Classifications
Botanically, a fruit is the mature, ripened ovary of a flowering plant that contains seeds. This means that any seed-bearing structure developed from the plant’s flower is classified as a fruit, encompassing a wide variety of forms from sweet apples to savory tomatoes. In contrast, a vegetable refers to any other edible part of a plant, such as roots, stems, leaves, or flower buds. Examples include carrots (roots), celery (stems), lettuce (leaves), and broccoli (flower buds).
A true nut, in botanical terms, is a specific type of dry fruit with a hard, woody shell that encloses a single seed. An important characteristic of a true nut is that its shell does not split open at maturity to release the seed. Botanical examples include the hazelnut, chestnut, and acorn.
Common “Nuts” and Their True Identities
Many popular “nuts” are not botanically true nuts; instead, they are classified as drupes. A drupe is a type of fruit characterized by a fleshy outer layer, a hard inner shell (called an endocarp or pit), and a seed inside. While the outer fleshy part of drupes like peaches or cherries is typically consumed, with almonds, walnuts, pecans, and pistachios, the hard inner shell is discarded, and the seed within is eaten.
Almonds, for instance, are the seeds found inside the hard pit of a drupe, which is covered by a leathery hull. Similarly, walnuts and pecans are also considered drupes, or sometimes “drupaceous nuts,” where the edible part is the seed encased within a tough shell. Pistachios are another example, botanically classified as drupes with a fleshy hull surrounding their hard shell and green seed.
Cashews present a unique case. The cashew “nut” is actually the seed of a drupe that develops externally to the cashew apple, which is an accessory fruit or pseudofruit. The cashew apple itself is often consumed in various forms, though less commonly in many Western countries.
More Culinary Quirks and True Nuts
Peanuts, despite their name, are not botanical nuts but are legumes. They belong to the same plant family as beans and lentils, and uniquely, their pods develop underground after the flower self-pollinates.
Coconuts are another example of a food often misidentified, as they are botanically classified as drupes. Like peaches and olives, coconuts possess a fibrous outer layer (exocarp and mesocarp) surrounding a hard inner shell (endocarp) that encloses the seed.
Hazelnuts, chestnuts, and acorns fit the strict botanical definition. These dry fruits contain a single seed and do not naturally open to release their seeds when mature. Botanical classification reveals many familiar foods have more complex identities than their common names suggest.