Classification of fruits

Philip, did you know that apples are not real fruits? But... what’s a real fruit then? Good question Philip… think about it, what would you call a fruit? You might be thinking of plants that have a pulpy, sweet-tasting flesh that surrounds the seeds?

Like oranges, mangoes and even apples. But scientists who study plants, botanists, define fruit in a different way. They define fruit as something that develops from the fertilised parts of the female reproductive organs of the plant, the ovaries. This means that some things we don’t usually consider fruits, like tomatoes, cucumbers, green beans and walnuts are actually fruit too! Botanists classify different types of fruit based on what they form from, and their internal structure.

Botanists usually talk about three main categories of fruit. The first one is simple fruit. Simple fruit form from a single ovary, and they may contain one or many seeds. Simple fruit are further split into fleshy and dry fruit. The largest group of fleshy fruit, is the berries.

Berries have fruit tissue, or pericarp, around the seeds. The inner layer of this pericarp is the pulp, or mesocarp, which is fleshy and juicy. The mesocarp is covered by the exocarp, which acts as a protective layer of peel. Examples of berries are blueberries, but also tomatoes, bananas, avocados and even lemons! Another group of simple fleshy fruit are those with one single seed in the middle.

The seed is buried in the stone of the fruit, the endocarp. Outside this is the fleshy mesocarp and then the thin exocarp. This group is called drupes, and includes fruit like peaches, plums and walnuts. Dry simple fruit, also form from single ovaries, but none of the pericarp layers is juicy or fleshy. Most legumes, like soybeans or peas, are examples of dry fruit, even if we usually consider them to be vegetables.

The second category of fruit, is the aggregate fruit. Aggregate fruit develops from several ovaries that grow in one flower. Aggregate fruit can often be juicy and have a fleshy pericarp, such as raspberries. Finally, there are so called multiple fruit. Multiple fruit are initially single fruit, growing from ovaries in individual flowers.

These flowers grow very close together, so as the fruit grow, they merge into one large single fruit. Multiple fruit often have a fleshy pericarp. Examples of these are pineapples and figs. So why are apples not considered real fruit? Well, because they don’t only form from the fertilised ovaries.

These types of fruit form when another part of the plant, usually a part of the stem that is directly connected to the flower - the receptacle, grows, swells and surrounds the fertilised ovaries. This is why apples are classified as false, or accessory fruit. Real fruits or not, I think apples are delicious!