In botany, a fruit is primarily defined as the ripened ovary of a flower, which encloses the seeds. The botanical definition centers on the plant structure from which it develops, a classification that often contrasts sharply with how we use the term in the kitchen. An accessory fruit, however, is a category of fruit where the edible, fleshy part is not derived solely from the ovary but includes tissue from other floral parts.
How Accessory Fruits Form
The development of an accessory fruit begins with the flowering and subsequent fertilization of the plant. After the ovules inside the ovary are fertilized, hormonal signals trigger not only the ripening of the ovary but also the expansion of adjacent floral tissues. These non-ovary tissues swell, becoming the bulk of the final, fleshy structure.
These accessory tissues can originate from several parts, most commonly the receptacle, the hypanthium, or the calyx. The receptacle is the thickened part of the flower stalk from which the floral organs grow, while the hypanthium is a cup-shaped structure formed by the fusion of the bases of the sepals, petals, and stamens. In certain flowers, particularly those with an inferior ovary, the tissue surrounding the base of the flower is genetically predisposed to expand and accumulate sugars and water. This simultaneous development of the ovary and the surrounding structures leads to the formation of the completed accessory fruit.
The Key Difference from True Fruits
A true fruit is formed exclusively from the mature, ripened wall of the flower’s ovary. This ovary wall develops into the pericarp, a structure composed of three layers: the exocarp (outer skin), the mesocarp (middle flesh), and the endocarp (inner layer surrounding the seed). This process means that every part of a true fruit, such as a tomato or a peach, is derived from the original ovary tissue.
Accessory fruits, conversely, incorporate significant extra floral components in their structure. They may still contain the ripened ovary and its seeds, but the prominent, fleshy portion that is typically consumed originates from the receptacle or hypanthium. These fruits are sometimes referred to as pseudocarps or false fruits because the majority of their mass is botanically external to the ovary. The classification dichotomy highlights that the source of the ripened tissue is the defining factor in botanical fruit categorization.
Notable Examples of Accessory Fruits
One of the most widely recognized accessory fruits is the strawberry, where the large, red, juicy flesh is formed by the greatly enlarged receptacle. The actual true fruits of the strawberry are the tiny, seed-like specks embedded on the surface, which are technically achenes. Each achene is a dry fruit derived from a single ripened ovary.
Apple (Pome)
The apple is a type of accessory fruit known as a pome, where the fleshy part is derived from the hypanthium. The edible crisp flesh surrounding the core is the ripened hypanthium tissue that fused with the ovary wall during development. The true fruit of the apple is the papery core that encases the seeds, which is the part that developed directly from the flower’s ovary.
Fig (Syconium)
The fig is a unique accessory fruit where the entire fleshy structure, called a syconium, is a closed, inverted inflorescence, or cluster of flowers. Inside this fleshy structure are hundreds of tiny flowers. The crunchy bits often mistaken for seeds are actually the numerous minute true fruits, each containing a single seed, lining the inner wall.