Eli5: Why do some plants flower briefly before growing vegetables? Do some flowers have vegetables we don’t eat?
In: Biology
I assume you mean vegetables with seeds inside such as squashes, cucumbers etc rather than the root or leaf vegetables? In terms of the plant, these structures with seeds inside are actually the fruit.
A fruit is a plants way of spreading its seeds. If a fruit is delicious, a creature will eat it and then poop out the seeds far away from the parent plant, so they can sprout and make new plants over a wide area. Humans have hijacked this by selectively breeding plants for the best fruit, even though we don’t spread their seeds in this way.
A plant flowers to attract pollinators. The bee (or whatever) is attracted to the flower, comes to drink the nectar inside, gets covered in pollen (the plant equivalent of sperm) and then spreads this pollen to the next flower. The pollen can fertilise the seeds in this plant and that stimulates the plant to develop fruit so that a hungry animal with eat it and spread its fertile seeds. So in this way, the flower is necessary just before the vegetable.
Which vegetables do you have in mind? Vegetables can be split into quite a few different categories, and some are the direct result of flowering (fruit-vegetables, eg tomatoes), while others take being fertilised as their cue to make a vegetable, and yet others I’d imagine just happen to flower and vegetabler based on the same environmental cues.
Also, you can’t really have vegetables we don’t eat, because the definition of “vegetable” usually includes eating them, such as “Plant matter that humans eat”. If we don’t eat it, it ain’t a vegetable. Which means that if suddenly everyone on Earth woke up tomorrow and adamantly refused to eat potatoes ever again, potatoes would stop being vegetables.
Flowering is just part of a plants reproductive cylce.
The vegetables you eat that are produced by the flower are fruits, you’re eating the fruiting body of that plant. Things like cucumbers and squash.
We eat other vegetables that do not come from the fruiting body of the plant, things like celery, carrots, leeks.
Flowers are billboards slash landing pads for pollinators like bees and other insects. Plants need to share genetic material just like animals, but unlike animals they can’t move to get close enough to do it. One way is to just blast pollen out into the air and hope some of that pollen lands inside the reproductive organs of the same species of plant.
Millions of years ago, plants evolved another way: borrow the animals to do it. Animals come close to the plant, get some pollen on them, and then fly or crawl to another plant and deposit that pollen. To entice animals to do this, plants produce sugary nectar that is high in calories. The nectar is kept near the stamen, which is the part of the plant where pollen is. To advertise that the plant has nectar, the plant produces a colorful flower that stands out. Animals see the bright flowers and come for nectar, get some pollen, carry it to another flower, and deposit some of the pollen there.
The pollen is deposited into the ovary or ovaries, which are also part of the flower. Some species of plants have separate male and female flowers, some plants have both male and female parts in the same flower. Either way, once the flower is pollinated, the petals will either die or curl up to be used to make seeds and a fruit.
Fruits are another evolution of plants to borrow animals. Plants need to spread out so they have access to more food. Think about a cow standing in the same spot: it will eat all the grass it can reach and then run out of food. If it has a calf, that calf won’t have food, either. Plants need space to grow and nutrients in the soil. Since they’re already using it there isn’t any room for a new plant to grow there. They need to spread out as much as possible.
Fruits are high in sugar and other nutrients, so animals come to eat them. The fruit is digested, but the hard seeds are not and pass through the digestive system. The animal carries the seed around in their gut until they poop the seed out somewhere else, presumably far away from the parent plant. Animal gets a meal, and the plant gets to spread out – win win!
Plants generally do not want to be eaten except for the fruit. There are some plants have have evolved other ways of spreading, like seeds carried by the wind or seeds with burrs that get caught on animal fur. These plants may or may not have edible parts. In fact, there’s a fairly good chance they’re poisonous to discourage animals from eating them. Other plants specialize on which animals eat them to make sure they get spread out and the seeds don’t get crushed or broken open. Those seeds may be poisonous to humans and other animals, but safe for whatever animal that plant evolved to use. Many fruits are edible but unpalatable – they won’t hurt you, but they won’t taste good and aren’t worth eating.
So there is one distinction that needs to be made here. If you are looking at plants from a botanical perspective, a fruit is what develops from a flower as it contains seeds and is involved in the reproduction process, whereas vegetables are the other parts of the plant (stem, leaf, root, etc). From a culinary perspective, fruits and vegetables are divided by taste. So flowering is a method to attract pollinators to pollinate the egg inside the flower which is responsible for creating the seeds to create more baby plants. The fruits that form around them are usually a way of safely pocketing this seed until they can spread.
There are many fruits that are inedible to humans. Some include asparagus berries, holly and nightshade.
Not to be too technical, but if you eat the part that had a flower, that’s a fruit. Yes, tomatoes are a fruit. A vegetable is when we eat a non-flower-based part of the plant, like a root (carrots and potatoes) or a stalk (like celery).
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