Everyone knows an apple is a fruit. What about a hazelnut or an eggplant though? They both come from plants, but one's a nut and the other's a vegetable, right? What about a grain of wheat?

A World Of Fruits

To botanists, all of these foods are fruits. That's because botanists define fruits as ripened ovaries along with their contents and adhering accessory structures. A number of the vegetables, nuts, beans, grains, and so-called seeds we eat fit this description, and so despite what your cookbook calls them, they're fruits.

Fruits are products of flowers and usually develop as a result of a flower being pollinated. Fruits are basically seed containers and seed disseminators. Some plants, however, develop fruit without fertilization, a process called parthenocarpy. These fruits are seedless.

Flowering Fruits

How do fruits form? In general, soon after a flower is fertilized, its ovule begins to form into a seed. The flower's petals fall off, and the ovary, which surrounds the ovule, swells. As the seed matures, the ovary or fruit ceases expanding.

There are numerous types of fruit, which can be grouped into three basic categories: simple fruits, aggregate fruits, and multiple fruits. Simple fruits are the products of flowers containing just one pistil, the main female reproductive organ of flowers. A pistil includes an ovary and an extension called a style, which is topped with a stigma. The stigma is what receives the pollen for fertilization.

Simple fruits include sunflower seeds, walnuts, peas, beans, wheat, tomatoes, apples, avocadoes, cherries, olives, and bananas, to name several. Aggregate fruits develop from flowers with multiple pistils, and include blackberries and strawberries. Multiple fruits develop from a cluster of flowers and include pineapples and figs.