The common understanding of a “nut” often differs significantly from its botanical definition, leading to confusion. Many items we commonly call nuts, from almonds to peanuts, do not fit the strict botanical criteria. This distinction helps clarify the diverse ways these popular foods develop in nature.
Botanically Speaking: What is a True Nut?
A true nut is a specific type of fruit. It is characterized as a dry fruit that contains a single seed, enclosed within a hard, woody shell. A defining feature is that this shell does not open at maturity to release the seed. This means the entire fruit, with its seed enclosed, falls from the plant as a single unit. The hard outer layer remains closed.
The Tree-Dwelling Nuts: Examples and Characteristics
Many familiar items we call “nuts” do indeed grow on trees, yet their botanical classification varies. True nuts that originate from trees include chestnuts, hazelnuts (also known as filberts), and acorns. Acorns, from oak trees, were historically an important food source, often processed to remove bitter tannins.
Other tree-growing “nuts” commonly consumed are not true nuts botanically but are instead classified as drupes or seeds. Walnuts, pecans, and almonds are botanically considered drupes, which are fruits with a fleshy outer layer surrounding a hard pit, or “stone,” containing the seed we eat. Walnuts are part of the Juglandaceae family, which also includes pecans and hickories, and they grow on trees. Cashews are another example, botanically seeds that grow from a “cashew apple” fruit on a tree. Despite these botanical distinctions, they are widely referred to as “tree nuts” in culinary contexts due to their similar characteristics and tree origin.
Beyond the Trees: Other “Nuts” and Their Origins
Not all foods commonly called “nuts” come from trees or fit the botanical definition of a nut. Peanuts are a prominent example, which are not nuts at all but legumes, belonging to the same family as beans and lentils. Peanuts grow underground in pods, unlike tree nuts that develop above ground. This unique growth habit is why they are sometimes called “groundnuts.”
Pine nuts, frequently used in dishes like pesto, are another case. These are edible seeds harvested from the cones of various pine tree species, not true nuts. Approximately 20 species of pine produce seeds large enough for commercial harvesting. Similarly, Brazil nuts are also seeds, specifically from a large tree native to the Amazon rainforest. These seeds are contained within a woody, spherical fruit that can weigh up to 2 kg. While these examples are not botanically true nuts, their hard coverings and nutritional profiles often lead to their culinary classification as such.