onions have layers

Why Do Onions Have Layers? How Many Layers?

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Onions have an interesting and unique structure that you might not have noticed before. They are full of flavors and also possess a variety of physical characteristics that give them the ability to store nutrients under their papery layers. 

But why exactly do onions come with multiple layers? Onions are bulbs, which means that they grow from a single bud that is located at the base of the onion. As the onion grows, new layers of cells are added to the outermost layer, causing it to expand and form a bulb. As a result, you can expect to find 9 – 13 layers when peeling an onion. 

In this blog post, we’ll explore the science behind onion anatomy, discussing everything from layer count to nutrient storage capacities. By understanding what makes up an onion, we can get closer to unlocking its flavorful potential!

Why Do Onions Have Layers?

Onions are extremely popular in cooking. They come in different varieties and can be used to enhance various dishes. One of the most distinctive features of onions is their layered structure.  

Protective Function

The layers of an onion serve a protective function. The outermost layer of the onion is thin and papery, and it is made up of dead cells. The purpose of this layer is to protect the onion from external damage, such as pests, bacteria, and fungi. 

The outer layer also helps to prevent moisture loss, which can cause the onion to dry out and spoil.

The layers beneath the outermost layer contain living cells that are responsible for the growth and development of the onion. 

These inner layers are thicker and more fleshy, and they provide support and structure to the onion. The layers also contain nutrients such as carbohydrates, fiber, and vitamins that are essential for our health.

Formation of Layers

The formation of layers in an onion is a result of the way the onion grows. The layers of an onion are created through a process called mitosis, which is the division of cells. 

As new cells are formed, they push the older cells outward, creating new layers. The process of mitosis continues until the onion reaches maturity.

The layers are made up of living and dead cells that provide support and structure to the onion while also containing essential nutrients. 

The Number of Layers in an Onion

To understand the number of layers an onion has, it’s important to know its anatomy. An onion is composed of several layers of thin, papery skin that surround the fleshy, edible bulb. 

The bulb is made up of concentric layers that are separated by a thin membrane. Each layer of the bulb is composed of tightly packed, fleshy leaves that are rich in nutrients and flavor.

The number of layers in an onion can vary depending on the size of the bulb and the variety of the onion. Generally, an onion has between 9 and 13 layers. However, some larger onions can have up to 25 layers, while smaller onions may have as few as five layers.

The layers of an onion are important for both flavor and texture. The outermost layers of an onion are usually dry and papery and are used to protect the inner layers from damage. 

The inner layers of the onion are more tender and juicy and contain the majority of the onion’s flavor. When cooked, the layers of an onion soften and caramelize, adding a rich, sweet flavor to dishes.

Do Green Onions Have Layers? 

Green onions, also known as scallions, are a common ingredient in many Asian dishes. They are often used for adding a mild onion flavor to soups, salads, and stir-fries. 

Green onions are a type of Allium vegetable, which also includes garlic and shallots. The structure of green onions is similar to that of regular onions, but with some differences. Green onions have a long, slender, white base that gradually tapers into a green stalk. 

The white roots of a green onion are called the bulb, and it is made up of tightly packed layers of modified leaves. These layers are not visible, as they are covered by the outermost layer of the bulb, which is usually white or light green in color.

green onion

So, do green onions have layers? The answer is yes! Green onions have layers just like regular onions, but they are not as pronounced. The layers of the bulb are tightly packed, which makes them difficult to see. But if you cut a green onion crosswise, you will be able to see the layers. 

The layers become more visible as you move up the stalk, where the green part of the onion is located. The green part of the onion is made up of long, thin leaves that grow in layers from the center of the stalk.

The white part of the onion is milder in flavor and is often used in soups, stews, and stir-fries. The green part of the onion is more pungent and is often used as a garnish or in salads. Green onions are also a popular ingredient in Mexican, Chinese, and Japanese cuisine.

What Is the Outer Layer of an Onion Made Of?

While onions come in different types and colors, all onions have one thing in common: layers. The outer layer of an onion is the first thing we see and touch, but what is it made of?

The outer layer of an onion is made up of dead cells that protect the onion from damage and disease. These cells are thin and papery and are composed of a substance called cellulose. 

Cellulose is a type of carbohydrate that is found in the cell walls of plants. It is strong and rigid, which acts as an excellent protective layer to preserve the inside layers of the onion for maximum flavor. 

Do You Need to Peel the Outer Layer of an Onion?

Onions are a key ingredient in many recipes, and they are used in various forms, such as sliced, chopped, or diced. However, when it comes to peeling an onion, it is not always clear whether you should remove just the papery outer layer or more. 

Yes, You Should Peel the Outer Layer of an Onion

The papery outer layer of an onion is often dirty, and it can harbor bacteria, dust, and other contaminants. Therefore, it is essential to peel off the outer layer before using the onion in your recipe. 

Additionally, the outer layer can be tough and bitter, which can affect the flavor of your dish. By peeling off the outer layer, you can ensure that your dish has a milder and sweeter onion flavor.

No, You Don’t Need to Peel the Entire Onion

While it is essential to peel off the papery outer layer of an onion, you do not need to remove the entire onion’s outer layers. The onion has several layers; the outermost layer is papery, while the inner layers are fleshy and edible.

Therefore, you can remove the outermost layer and use the inner layers for your recipe. However, if you notice any soft or brown spots on the onion’s outer layers, it is best to remove those layers as well.

Uses for Onion Skin

After peeling, the skin of an onion is often discarded without a second thought. However, onion skin is more useful than you might think. In this article, we will explore five surprising uses for onion skin.

onion skin

Natural Dye

Onion skin can be used as a natural dye for fabrics. The brownish-yellow color of onion skin can be extracted by boiling it in water. The dye can be used on natural fibers such as cotton, wool, and silk

The color of the dye can be adjusted by adding more or fewer onion skins to the water. This is a great way to give new life to old fabric and create a unique, natural color.


Onion skin is rich in nitrogen and other essential nutrients that are great for composting. Adding onion skin to your compost pile can help to improve soil fertility and structure. 

onion skin in compost

You can either add the skins directly to the pile or mix them with other organic materials, such as grass clippings, leaves, and food scraps.


Onion skin can be used to make a flavorful stock. The skin contains a high concentration of quercetin, an antioxidant that has anti-inflammatory and anti-viral properties. 

To make onion skin stock, simply simmer the skins in water with your favorite herbs and spices for an hour or two. The resulting broth can be used as a base for soups, stews, and sauces.

Skin Care

Onion skin contains a compound called quercetin, which has been shown to have anti-inflammatory and anti-bacterial properties. These properties make onion skin a great addition to your skincare routine. 

You can use onion skin extract as a natural toner to help reduce inflammation and redness. Simply boil onion skin in water and use the resulting liquid as a toner.

One Comment

  1. Hi Jaron!

    I came across your blog post about onion layers, because I was researching how onion layers are formed. You explain ‘why’ and ‘how many’, but it is difficult for me to find an answer to ‘how’.

    I have a theory and just wanted to ask you, if you’ve heard of this before:

    I speculate that the layers are formed parallel to the phases of the moon and have a few reasons for that.

    First of all, the moon has a major influence on water (best example is the movement of the oceans/tides). Vegetables are made up mostly of water.

    As you wrote in your post, there are between 9 to 13 layers – the number of layers in an onion could explain how many moon cycles the onion was in the soil and growing. Let’s say, a winter onion planted in November and harvested in August the following year would have 12 layers (when you include about 2 layers of the onion set). Or, a two-layered onion set planted in March and harvested in September would result in a 9 layered onion.

    Often the first couple of inner layers of an onion a thicker than the outer layers, again that could be explained by the moon’s influence. Spring tides are higher, because the moon is closer to earth and her gravitational pull stronger.

    Spring onions have the same layers, but of course there are only 3 or 4, which could again be explained with the growing period – 3 or 4 moon phases.

    We can see the same rings in leek of course, but also in beetroot.

    The same pattern of layers can be seen on a tree trunk, but here of course it is the sun’s influence on forming the rings, not the moon. But the principle could be the same – are the onion layers formed parallel to the moon’s cycle?

    I just wanted to know if you’ve heard of this theory before.

    Thank you and have a great day!
    Kind regards

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