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Do Onions Grow Underground? (Answered)

Who doesn’t like to plant onions, right? It requires low maintenance and can fulfill our day-to-day vegetable needs.

That being said, while planting the onions, you might wonder if they grow underground or above the ground. Let’s find the answers to all your queries regarding onions growing underground.

Do onions grow underground?

Onions grow both below and above the ground. The onion bulbs grow underground and the green onions grow above the ground. The underground growing bulb is the main part of the onions and gardeners plant onions mainly for this. However, green onions are also edible and a widely used vegetable.

Will onions grow underground?

By onions, we mainly think of the onion bulbs, which are the most commonly used part of the onion. This bulb can be purple, white, red, yellow, or even brown. The bulb grows below the surface. So, the onions will basically grow underground.

However, not every part of the onions grows under the ground. The green top, also known as green onions, grows on the surface. These are also edible just like the onion bulbs.

The onion bulbs are picked from underground once the green onions turn yellow and fall over. It takes almost 150 days for the onion top to detach from the leaves. After harvesting the bulbs from below the surface, they can be peeled, sliced, and eaten fresh.

If you cut the onion tops before turning yellow, the onion will not grow perfectly underground. However, it can still be used in vegetables and salads.

Do all onions grow underground?

Not every type or part of onion grows underground. However, most of their parts grow below the ground.


The red onions are slightly pungent-flavored and sweet. These are the most common types of onions that develop below the ground. They can be harvested from underground after five to six months of planting.


Spring onions are one of those parts of onion that grows on the surface rather than underground. They can grow from 30 cm to 50 cm above the ground


White onions are basically white bulbs of onions. They grow underground and can be picked when the onion top turns yellow.


Yellow onions are quite rare and they mostly grow in northern latitudes. Just like every other onion bulb, they also grow below the surface.


The green onions, also known as scallions generally grow on the surface. They don’t develop enormous underground bulbs. They’re planted just like the bulb onions, but they’ll be fully ripe a lot sooner.


The purple bulb onion grows completely below the ground. This type of onion generates huge underground bulbs that are purple in color. They become perfect for harvesting from underground after six months on the plantation.

How far underground do onions grow?

The onion bulbs don’t grow too far underground. They are planted one or two inches deep into the ground. The bulbs don’t grow any further down than two inches, they develop roots that help them get nutrition and water.

The root can grow from 18 to 36 inches deep under the ground.

How does onion grow?

Onion can be grown from seeds, immature bulbs, and transplants. They are quite easy to grow and require very low care.

Growing the onion from an existing onion bulb is the easiest because you won’t have to go through the process of choosing a high-quality seed or transplant.

To grow onions from immature bulbs or existing onions, first, chop 2.5 cm off from the bottom. While doing so, take off the outer peel from the bottom. You can just keep the 2.5 cm part for plantation and use the remaining part of the onion for cooking.

Then, leave a separated part of the onion for 24 hours to dry out completely.

When the bottom is dry to the touch, insert toothpicks on all the sides of the onion, maintaining equal distance from each other. Then, hang it over a bowl filled with water. It will start growing roots after 3 to 4 days of placing.

Now that your onion part has started to grow roots, it’s time to plant it on a pot. Before planting the onion part in the pot, fill the pot halfway with high-quality and well-draining soil.

Then, place the part of the onion in the half-filled pot and cover it with soil. Water the soil adequately and spray nitrogen fertilizer into it.

Once the onion starts growing leaves, take it out from the pot carefully and place it on the soil of the garden. Water the soil at least once per week and fertilize it once every two weeks.

When the onion plant starts blooming, it’s the right time to pick the bulb onions. With your shovel, loosen the soil surrounding the onion and take it out of the ground by the base.

How do onions reproduce?

Onions develop bulbs in their first year of the plantation, which can be harvested according to necessity. Unlike other vegetables, they reproduce in every method possible. They can reproduce through the seed to seed method, bulb to seed method, pollination, and more.

Onion flowers require pollination to reproduce just like other seed-producing plants. At separate times, the male and female sections of the onion bulb grow, which is excellent for the cross-pollination of insects.

The honey bees are not attracted to nectar because onions’ flowers don’t have honey, flies are the ideal pollinators of onions.

The onions can also reproduce by the bulb to seed reproduction method. By this method, you can grow the same type of onion as your preferred onion variety.

The seed-to-seed onion reproduction is less time-consuming and less expensive than some other methods. You can also choose from a number of crops to suit your particular demands.

In this method, you only leave the seeds in your garden, to grow in bulbs and bolts.

Can you grow an onion from an onion?

You can definitely grow an onion from an existing piece of onion.

In fact, growing onions from onions are the most effective and easiest method. The onions grown from the bulb onions are the least disease-prone and become ready to be harvested in the shortest period of time.

How to grow onions from onions?

Growing onions from onions are quite simple, you can do it with a little effort and time. To cultivate onion from an onion, you will have to chop a 1-inch slice from the bottom. Then, you will have to dry it and hang it over a bowl filled with water using toothpicks.

When the onion bottom starts growing roots, transfer it to a pot or gardens’ soil. Water and fertilize it on a regular basis, and your onion will be ready to pick after a couple of months.

How long do onions take to grow?

Onions take almost 100 to 125 days to grow and become ready to harvest. However, it takes this long only for the bulb onions to grow. The green onions, also known as spring onions, take only 3 to 4 weeks to fully grow.

How do I get my onions to grow bigger?

You can get your onions to grow bigger by planting them at the right time. You should plant them in late summer so that you can avoid spoiling or sun damage.

Onions can grow quite big in soil that is heavy in nitrogen. So, to give your onion the nutrients it needs to grow bigger, spray nitrogen fertilizer into the soil.

How many onions do you get from one plant?

In general, you can get only one onion from one plant. However, there is a type of onion plant known as the multiplier onion or potato onion, in which around five onions grow in each plant.

How do I know when my onions are ready to harvest?

When the green onions or onion tops start becoming yellow and fall apart, it is ready to harvest. You can also know that your onions are ready to be picked once they start growing flowers. Usually, the onions become ready to harvest after 3 to 4 months of planting.

Final Thoughts:

Most of the onions grow underground. However, not every part of the onion grows below the ground, some part of them grows on the surface as well. The green onions or spring onions grow above the ground. The red, purple, yellow, or white onions grow one or two-inch deep inside the ground.