What's the difference between fruits & vegetables?

The deal with fruits and vegetables: We think of fruits as sweet, and vegetables as savory. Botanically, however, it’s a completely different story. And that's because fruits have a very strict botanical definition, the word ‘vegetable’ doesn’t mean anything in botany.

Image: Marco Verch Professional Photographer 

Vegetables can come from any part of the plant - eggplant, zucchini, and tomatoes are all fruits, but carrots and radishes are roots, potatoes are underground stems, lettuce and onions are leaves, and broccoli. Fruits, on the other hand, refer to one specific part of the plant in botany: they're mature plant ovaries! Now to really understand the true meaning of fruit, we're going to have to do a deep dive into plant reproduction specifically, flowering plant reproduction, because only flowering plants make fruits. So you won’t see a fruit on a moss, fern, or pine tree.

Flowers contain the plant’s reproductive organs. Stamens are the male organs - their anthers make pollen, which contain sperm cells. The carpels are the female organs - they consist of a stigma, style, and ovary. In the ovary, you’ll find ovules that each contain an egg. The sepals and petals serve to attract pollinators that move pollen from the anthers of one flower to the stigma of another flower. Sperm from the pollen travel down the style and into the ovary, where they fertilize the eggs in the ovules. Each ovule will mature into a seed. 

The fertilized egg develops into an embryo, aka a baby plant, inside the seed! It remains dormant until the seed can move away from the parent plant and find an ideal spot to germinate and grow. And how does it move away?? The fruit! The ovules are becoming seeds inside the ovary, which itself is maturing into a fruit. So, the purpose of fruits is to disperse seeds! Plants want their offspring to spread as far and wide as possible make sure their survival. Fruits come in every shape and size imaginable to take advantage of every dispersal method imaginable - some fruits are juicy and delicious so they get eaten by animals that will poop out the seeds later; some fruits have spikes to help them hitch a ride on a passing critter; some are aerodynamic and can soar through the air; and others can float on the seas. Botanists could fill a dictionary with terminology just for describing these different types of fruits.

Fruit tissue is called pericarp, and consists of three layers: exocarp (the outer layer), mesocarp (the middle layer), and endocarp (the inner layer). Fruit types are defined based on the characteristics of these pericarp layers, as well as the number of ovaries a flower has. A berry is a fruit with a completely fleshy pericarp that came from a flower with a single ovary A tomato is a great example - and if I cut it open, we can see that all the layers are soft and fleshy - the skin is the exocarp, we have the mesocarp, and a pulpy endocarp Avocados are berries - the leathery exocarp still counts as soft. And, blueberries are actually berries! So, not everything is a lie. You can see there are no rules about seed number - a single ovary can contain multiple seeds, or just one Citrus fruits are a special type of berry called a ‘hesperidium.’

The entire rind of the orange is actually all three layers of the pericarp so, what are we eating when we eat an orange? Well, it turns out that citrus fruits are lined with tons of special hairs that are filled with juice - so when you eat oranges you're biting into a giant ball of plant ovary hair. Peaches, plums, and nectarines may look like berries, but they are actually a different type of fruit called a “drupe”. And if we cut it open, you'll see why only the exocarp and mesocarp of drupes are fleshy. The endocarp is hard and stony. So I used to think this was just the seed, but it’s actually the innermost layer of the fruit, and the seed is inside of that. Once you crack it open, then you’ll find the seed inside. You will see that the endocarp has a little chamber inside, and that's where the seed was! Nuts are fruits with completely dry pericarps that are indehiscent. That means that they don’t open up to release their seeds. So peanuts don’t count because while they’re completely dry fruits too, they are dehiscent, meaning that they open up to reveal the seeds we eat.

Walnuts and almonds are seeds that come from drupes! True nuts are things like acorns and chestnuts. But what happens when a flower has more than one ovary? You can see this blackberry flower has tons of carpels - each one has an ovary that will make a fruit, and as they grow and ripen they all get kind of stuck together and you wind up with a blackberry. This is called an ‘aggregate fruit.’ Each individual fruit on the blackberry is actually a little drupe, so blackberries are aggregates of drupelets, which is the cutest word in botany, ever. You can also have the opposite situation, where single ovaries from multiple flowers all combine into one fruit - this is fittingly called a multiple fruit Anyone want to guess what a cool example is?? 

Pineapples! So this used to be a stem with lots and lots and lots of flowers on it All the different segments are single ovaries from all these different flowers that have all fused together into this beautiful pineapple isn't that so cool?? Strawberries are a whole other story - the delicious part of the strawberry isn't a fruit at all! It's the base of the flower, called the receptacle that swells and grows and becomes red and sweet. The actual fruits of the strawberry are all the things you probably think are seeds on the surface of the receptacle!

Now, a confession: I too have lied to you about fruit. Remember this? Just love a good plant ovary well, similarly to strawberries, the delicious part of the apple is receptacle tissue only the core of the apple is fruit, so I wasn’t actually biting into the ovary here. The crunch was just too good to pass up! But, I am very sorry to have misled you. Well I hope this article has given you some newfound respect for fruits and sympathy for vegetables.

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