Many people use the term “nut” to refer to any hard-shelled, edible kernel. While commonly associated with trees, not all “nuts” grow on branches. This article explores the botanical distinctions and growth habits of various tree-grown “nuts,” clarifying which are true botanical nuts and which are culinary conveniences.
Understanding What a “Nut” Is
The common understanding of a “nut” often differs significantly from its botanical definition. In culinary terms, a nut is generally any large, oily kernel found within a shell, used in cooking. This broad definition includes items like almonds, walnuts, and peanuts, which are not botanically true nuts. Botanically, a true nut is a dry fruit with a single seed, a hard shell, and a protective husk. Importantly, it does not open to release its seed when mature. This distinction is fundamental to understanding which “nuts” truly grow on trees.
True Botanical Nuts from Trees
Only a few common “nuts” qualify as true botanical nuts that grow on trees. These include acorns, hazelnuts (also known as filberts), and chestnuts. Acorns are the fruits of oak trees, developing within a cup-like structure with a hard, non-splitting shell enclosing a single seed. Hazelnuts grow on hazel trees, maturing as small, round to oval nuts encased in a leafy husk. Chestnuts, produced by chestnut trees, are characterized by their spiny burrs that split open to reveal the smooth, hard-shelled nuts inside.
Common “Nuts” That Grow on Trees
Many popular culinary “nuts” that grow on trees are not true botanical nuts but are instead classified as drupes or seeds. Almonds, for instance, are the edible seeds of a drupe, a fleshy fruit like a peach or cherry where the seed is surrounded by a hard shell. Almond trees (Prunus dulcis) produce these fruits with an outer hull and a hard internal shell.
Walnuts and pecans are also botanically considered drupes despite their hard shells. The walnut tree (Juglans regia) produces a fruit with a green outer casing that splits open to reveal the familiar hard-shelled walnut. Pecans (Carya illinoinensis) are likewise drupes, with a husk that dries and splits to release the “nut.”
Cashews and pistachios are other examples of tree-grown “nuts” that are not botanically true nuts. Cashews are seeds from the cashew tree (Anacardium occidentale), developing at the end of a fleshy cashew apple. The kidney-shaped cashew “nut” is a drupe that forms before the apple fully expands.
Pistachios, from the Pistacia vera tree, are also seeds from a drupe. Their fruit has a fleshy outer layer that surrounds a hard shell containing the edible green seed, which often splits open when ripe.
“Nuts” That Don’t Grow on Trees
Some common culinary “nuts” are not associated with trees at all, most notably the peanut. Despite its name, the peanut is not a true nut; it is a legume, belonging to the same plant family as beans and peas. Peanut plants (Arachis hypogaea) flower above ground, but their seed pods develop and mature underground. After pollination, a specialized stalk called a “peg” grows downward, pushing the developing ovary into the soil where the peanut forms. This underground development distinguishes peanuts from tree-grown “nuts.”