Is there only one kind of edible nut?

Abstract

The term ‘nut’ is widely used for edible fruits or seeds that have a hard pericarp, but botanical authorities fail to agree on any aspect of its definition. We use a combined definition here to evaluate 22 species edible by humans and commonly called ‘nuts’, or with nut-like characteristics. The only fruit that meets the criteria is the hazelnut (Corylus spp.). The criterion least often included is that the fruit must be derived from a compound ovary, but even removing this restriction there are no other edible nuts. The vast majority of species of true nuts are not eaten by humans. The syndrome of a large, edible seed with hard outer covering derived from either the testa or pericarp is found in a wide range of families. It is an adaptation to animal dispersal by gathering, hoarding and forgetting, and is a notable example of parallel evolution.

Keywords:

• aril
• fruit
• morphology
• parallel evolution
• pericarp
• plant
• testa

Notes

¹‘legume’, but this is a type of follicle.