Fruit

Fruit. We all know what fruit is, right? Well, maybe not.

Ripe nectarines

There are vegetables that we call fruits, nuts that are fruits, and fruits that are not fruits at all! Before we get started, let’s look at why plants go to all the trouble to produce fruit in the first place.
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How fruit benefits a plant
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In the world of plants, reproduction is the name of the game. Characteristics that evolve to promote the likelihood of a plant surviving are passed on to the next generation. Fruit is one of those characteristics. Creating fruit takes a lot of energy from a plant. But the fruit we eat has evolved to protect, disperse, and feed the seeds within. As the fruit ripens and falls, the fruit provides protection and nutrients. Fruit also encourages birds, animals, and people to spread seeds farther than the plant could do alone.

Yellow cherry tomato

Pomegranate berries

Defining fruit
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Depending on who you ask, fruits can be several different things. The simple tomato provides a classic example:

• Most of us consider tomatoes to be vegetables. They are sold next to lettuce and broccoli, and we use them in savory entrees and salads. Using this definition, we are talking about ‘culinary fruits’.
• From a legal point of view, tomatoes are vegetables. (Nix. v. Hedden, 1893) That decision was made so that higher taxes could be collected.
• From a scientific point of view, botanical fruit is the (commonly) edible, seed holding, reproductive organ (ovary) of a flowering plant (angiosperm). 

Diagram of a typical drupe (peach) showing both fruit and seed (LadyofHats) Public Domain

Fruit specs

For something to be a botanical fruit, it must be the fertilized ovary of a flowering plant (angiosperm). After pollination and fertilization occur, two new structures are produced: seeds (fertilized ovules) and pericarp (thickened ovary walls). There are three different types of pericarp tissue: exocarp (outer skin), mesocarp (flesh), and endocarp (inner layer). The dominant pericarp tissue can become hard, as with nuts, or fleshy, as we see in peaches and avocados. In some cases, we eat the pericarp. In others, we eat the seed. When we eat the pericarp, we call it a fruit. Sometimes.

Fruit classification

Like most things in life, the more we learn, the less simple anything is. Fruit is no exception. Fruits can be simple, multiple, or aggregate. Rather than going too far down that rabbit hole, let me summarize by saying simple fruits, such as apples and tomatoes, develop from a single ovary. Pineapples and figs are multiple fruits, which form when separate flowers cluster together. Aggregate fruits, such as raspberries and blackberries, are clusters of multiple ovaries from the same flower. Make sense? But wait! There's more! To start, simple fruits are also classified as either dry or fleshy.

​Dry simple fruits

Dry simple fruits are not the shriveled backpacking fare variety. Dry fruits are made up of dead cells that either split open (dehiscent) or stay closed (indehiscent). Dehiscent fruits include hazelnuts, walnuts, pecans, sunflowers, corn, and wheat. Indehiscent fruits include beans and peas and other legumes, dill, poppies, and even cotton!

Indehiscent blue-podded peas

Dehiscent oats and wheat

Fleshy fruits

You might think you are finally in familiar territory, but that might be a mistake. The world of plant classification has been home to some bitter battles, and recent DNA analysis has turned many assumptions upside down. The fundamental categories of fleshy fruit are drupes, berries, aggregates, and multiples. Before you jump to any conclusions, check out these definitions for each category:

• Drupes - 1 or 2 seeds within a stony pericarp, surrounded by flesh (almond, plum, peach, walnut)
• Berries - 1 or more seeds with no stony pericarp (tomato, grape, citrus, cucumber, melon, kiwifruit, eggplant, banana, chili pepper, pomegranate)
• Aggregates - Several separate pistils of one flower fuse together (raspberries, blackberries)
• Multiples - Several separate pistils of several different flowers fuse together (pineapple, fig)

Unripe almond drupes

Aggregate blackberries

Fig, a multiple fruit

Pineapple, a multiple fruit

Nuts as fruits

Nuts are a strange case, when it comes to defining fruit. Some nuts are fruit, and some nuts are seeds. And some nuts, such as peanuts, aren’t nuts at all. Peanuts are legumes, which makes them indehiscent fruits. A ‘true nut’ is a hard-shelled pod that holds both the fruit and the seed, and the fruit does not open. True nuts include hazelnuts, acorns, and chestnuts. The other nuts are actually drupes. Drupes *dupe* us into thinking they are nuts, but they actually have a fleshy outer covering over top of the hard shell. Almonds, walnuts, and pecans are drupes, not nuts. But most of your friends will never believe you.

Apples are accessory fruits

Accessory fruits and non-fruit fruits

There are also accessory fruits, which are made not just from the ovary, but also from nearby tissues. Common accessory fruits include strawberries, rose hips, apples, and pears. We may as well run the gamut with this one. Rhubarb is considered a fruit, but we only eat the stems, which are technically vegetables.

Getting the best fruits from your garden

Healthy plants produce bigger fruit. Keep your plants healthy with regular inspections for pests and diseases, appropriate watering and feeding, regular pruning, and disposing of mummies as soon as they are seen.

As your fruit starts to ripen, you can make it sweeter by reducing irrigation.