An accessory fruit is a fruit that contains tissue derived from plant parts other than the ovary. In other words, the flesh of the fruit develops not from the floral ovary, but from some adjacent tissue exterior to the carpel (for example, from receptacles or sepal). As a general rule, the accessory fruit is a combination of several floral organs, including the ovary. In contrast, true fruit forms exclusively from the ovary of the flower.
Accessory fruits are usually indehiscent, meaning fruits that do not split open to release seeds when they have reached maturity.
Alternative terms for accessory fruit are false fruit, spurious fruit, pseudofruit, or pseudocarp. These are older terms for accessory fruit that have been criticized as "inapt", and are not used by some botanists today.
Glossary of botanical terms
Fertilization of accessory fruits induces the development of other organs; flower peduncle in cashew apple, calyx, bracts in pineapple, etc.
The following are examples of accessory fruits listed by the plant organ from which the accessory tissue is derived:
Hypanthium-derived: pomes (e.g. apple and pear)
Perianth-derived: anthocarps of the Nyctaginaceae
Receptacle-derived: fig, mulberry, pineapple, and strawberry
Sepal-derived: Gaultheria procumbens and Syzygium jambos
Fruit with fleshy seeds, such as pomegranate or mamoncillo, are not considered to be accessory fruits.
The part of apples and pears that is consumed is, in fact, the hypanthium. The ovary is the papery core that surrounds the apple seeds. As the hypanthium ripens it forms the edible tissues.
For roses, the hypanthium is the tissue that composes the edible part of rosehips (basically, the fruit of roses and eglantines). Roses and apples are members of the rosacea family; the fact that they have the same fruity morphology is a major consideration in placing them in the same taxonomic family.
The edible part of the strawberry is formed, as part of the ripening process, from the receptacle of the strawberry flower.