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Why Do Onions Have Layers? And How Many Layers Do They Have?

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Onions are notoriously difficult vegetables to cook with, mostly because they end up blurring your vision and leaving a strong smell even a couple of days later. To make things more difficult, onions have a whole set of layers you have to cut through. When you look at it, it’s rather strange.

Why do onions have layers, anyway ? And what do those layers do ? Does garlic have layers ? And why do raw onions cause gas and stomach aches ? Why are they sweet when cooked ? 

Onions are confusing as they are delicious, and they can instantly add a lot of flavor to any meal. So let’s take a closer look at this vegetable, since it’s in everyone’s kitchen.

onion layer

Why do onions have layers ?

Onions have layers because, as they grow, a new layer sprouts from the inner seed, and the outer layers die off. These layers are actually the beginnings of leaves, and above ground they are the long, green, fleshy leaves you see.

Onions grow in bulbs, and this means new layers will continue to form from the inside, pushing the older ones outward, until it is time to sprout a flower. Because of this, the outer layers of an onion are dehydrated and papery, and the inner layers are tightly packed together.

So when does an onion know to stop growing ? It stops growing, or producing more layers, when it’s time to form a flower. This means the weather and nutrients have to reach a specific level, for the bulb to mature and actually produce flowers.

Commercial onions are generally harvested before they produce flowers, and they have anywhere from 8 to 16 layers. The exact number of layers depends on the onion’s age and variety.

The case of spring onions

Spring onions are perhaps the best example of how an onion grows. A large, mature onion is round and bulbous-looking. A spring onion is long and thin, and the white end has not yet started to turn bulbous. 

The more you let an onion grow, the rounder the white part becomes, as new layers keep emerging. The innermost layers are the new green sprouts you see in the middle of a green onion. 

And when you cut a green onion, you’ll notice many layers simply coming off the white part. If you were to leave the onion to grow, those layers would thicken and become rounder, and the bulb grew. This is why ‘older’ spring onions are round-tipped and not as delicate in flavor. They’re simply maturing into their full, round form.

Read also: Can You Reheat Onion Rings ? 

spring onions

How many layers do you peel off an onion ?

When peeling an onion, you need to remove all the papery skins on the outside. Cut half an inch off the top, and a small bit from the bottom. Then look at the first layer you see, check it for imperfections like a soft texture, a moldy bit, or just being too thin and starting to peel off anyway. Remove that layer as well.

This way you’re left with onion layers that hold together very well, and are perfectly snug. This will make cutting up the onion much easier.

How many layers do onions have?

This answer really depends on the onion type and also differs from one onion to another but usually, you can expect 8-10 layers for a regular-sized onion. If they are all-natural the variation in the number of layers will be high since they don’t all grow the same if left on their own.

On the other hand, if they are not all-natural the chances are they will all have the same number of layers, we have all seen some funny onions that are the same size that you almost believe they are just for decor.

Why do onions sprout ? 

Your onions have started sprouting because they’ve been exposed to direct sunlight and moisture. If stored for long enough, onion bulbs will bring sprouting anyway, meaning you can safely grow your own onions at home. 

To keep onions from sprouting, keep them in a cool, dark, dry place that is well ventilated, to avoid any excess moisture the plant could use to sprout.

Why do onions cause gas ?

Onions can cause gas because they contain fructose, a type of sugar that some people may have a resistance to. In that case the fructose is not absorbed in the small intestine, instead traveling all the way to the colon. Their bacteria break down the fructose, leading to gas and painful bloating.

Not everyone experiences this, but those who do will usually find they are very bloated after eating fruit and vegetables, even if cooked.

Another reason onions can cause gas is because they contain dietary fiber. They contain less fiber than broccoli, cauliflower, and cabbage, but they still contain some, and thus can make you gassy.

Why are onions sweet ?

Onions are sweet when cooked because the natural sugars in them are still present, but in a smaller amount of cooked food. As you cook the onions, they sweat and reduce their size, because their moisture evaporates. But the fructose does not evaporate, so the cooked onions will always seem sweeter than the raw ones, full of moisture.

You can make onions sweeter by cooking them for longer, and actually caramelizing them. This process calls for a longer cook time, at a lower temperature. Otherwise, you risk scorching the onions.

If you want your onions less sweet, don’t cook them as long, and use red onions. Yellow and white onions are the sweetest ones. 

Read Also: How To Thicken Carbonara Sauce?

Why do onions smell ?

Onions have a specific smell due to their sulfur content. Just like garlic, onions draw the sulfur from the soil they grow in. This also influences how strong the onions taste, and how spicy they end up. If you were the remove the sulfur entirely, the onion would not taste of anything, and it would not smell. 

You can remove the smell of a cooked onion by wiping down the surfaces in the kitchen. The smell clings to oil and fat, so you’ll have to use something like lemon juice or dish soap to help things along. 

As for your skin, onion and garlic juice stick t it because they bond with the keratin on your skin, nails, and hair. It gets right in there and does not budge unless you flush it out with something like dish soap or shampoo. SO be sure to always, always wear gloves when handling onions, garlic, leeks, and similar foods. 


I hope this article managed to answer the question of why onions have layers and also how many layers you should expect an onion to have.

Also, the other common question people have about onions should be useful if you are doing more research about onions.

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