Did you know that onions grow underground? I didn’t either until I started researching the answer to this question. 

It turns out that onions are grown from bulbs, which are small round structures in the ground that house the roots of an onion plant. 

The real question, then, doesn’t do onions grow underground, but how do onions grow underground? To find out more about this process, keep reading to learn all about onion plants and their bulb formation.

Do onions grow underground?

No, onions grow underground only on a few rare occasions. The truth is that onions grow from tiny bulbs that reside on the soil’s surface or underground. You should grow them in full sun and keep the soil well-watered throughout the season. 

They will start producing leaves and flowers (the base for next year’s harvest) after the ground has warmed up. If you would like to save some of your onions for winter use, make sure to dry them properly before storing them in a cool dark place.


However, onions do require at least six inches of soil to grow properly and will often rot if their tops stay wet. Some varieties of onion, such as white and red onions, are grown above ground on mounds. 

Purple and yellow onions are also grown in this way. This way of growing them is advantageous because the soil needs to be replenished often and when it rains, the water doesn’t just wash away the dirt holding the crop up. 

That’s not the case with green onions which need a constant supply of moisture to grow so they are usually planted below ground.

How Long Do They Take To Grow?

It’s important to know how long it takes for an onion to grow before planting one. The difference in time depends on the variety of onions being grown, but all varieties typically take 3-8 months to grow before harvesting. 

An inch in the soil can equal a foot of growth, so that is something that people who are new at planting veggies should keep in mind when considering what type of space to plan for. 

Depending on the variety and the climate, some vegetables like cabbage might only need a few weeks to mature before harvesting.

There are many online calculators available for people to figure out how much food they want to produce each year and then estimate how much land they will need based on the crops chosen. 

Some plants don’t require as much room as others, so these tools can help homeowners or gardeners decide which types of plants will work best with their land size.

Are Onions Easy To Grow?

It depends on what variety of onion you’re planting, because there are some that are easier to grow than others. Red Candy onion is the easiest of all and doesn’t need a whole lot of fussing over. 

You just plant them, water them regularly and then harvest them at the end of their season. But even with easy-to-grow varieties, it’s better to sow your seeds in early spring (March or April) so they’ll have time to establish themselves before summer arrives.

If you want to wait until late spring or summer (April through July), then you should be able to plant the seeds right in the ground at that time as long as it’s sunny where you live.


How To Grow Onions? Entire Process

Onions can be grown at home in a wide variety of containers. Many people like to use terra cotta pots, and add a deep layer of soil on top before planting their seed onion. Seeds should be placed about two to three inches below the surface. 

Onions grow better when they’re transplanted, so once your onion reaches about four inches tall, gently pull it up by the roots and place it into another container of potting soil. 

This is done by inserting one hand beneath the onion’s roots while grasping the green stalk with your other hand, then carefully pulling up while avoiding breaking the roots or leaving behind any clumps of dirt. 

Once the root has been removed from its original container, tuck it into the new pot and continue adding soil until only an inch or two remains above ground. 

Remember that as onions grow taller, their bulbs will also get larger which will result in thicker layers of foliage growing on top – this is normal! As long as the base of the plant is healthy, these leaves will not have an adverse effect on the onion’s growth. 

To harvest your crop, simply dig down around each plant and clip off the leaves without removing any dirt around the bulb. Wash thoroughly with water (or submerge for 15 minutes) to remove all traces of soil before placing them in storage containers for preservation purposes.

Related Post – Are aphids harmful to humans?

When to Harvest Onions

Onions can be harvested after six to eight months of growth. As the plants mature, the bulbs will begin to rise from the ground. The bulb becomes firmer and develops a protective shell as it matures in late summer. 

If you dig an onion that is not fully mature, you may encounter a rotten smell. Onions that are more mature will not have a strong onion smell and oftentimes start to curl up around the edges as they dry out in late summer or early fall. 

Allow any moisture on newly harvested bulbs to dry before storing them in storage containers lined with paper towels or newspaper to help draw out additional moisture that may cause mold or rot if left untreated.

How Deep Do You Bury Onions?

Onions are semi-bulbous vegetables that are grown above ground. They have green outer skin and can range in color from light yellow to red. Generally, they grow in soil and should be planted with at least one inch of dirt covering the roots. 

However, if you want to make sure that your bulbs develop correctly, it’s best to plant them about two inches deep in the ground. It is essential for soil moisture levels as well as root growth. 

If the planting depth isn’t appropriate or if the weather is too hot, your onions may not produce enough flavor or even mature properly into its bulb shape.

How Many Onions Will One Onion Grow?

This is a difficult question to answer since there are many variables that go into it. Factors such as soil quality, soil moisture, light availability, temperature and the age of the onion plant can all affect the size of an onion. 

With this in mind, the average person should expect about 5 onions per plant for a small vegetable garden if everything is optimal for their onions. 

However, this number can vary drastically from one family’s garden to another depending on each family’s conditions. 

For those who have never grown their own before but would like to try it out, research your climate zone before starting out!


What Happens If You Leave Onions In The Ground?

Some people say that leaving your onions in the ground over winter might keep them from sprouting. This is because the onion bulbs remain dormant through the winter and emerge in spring, creating a new plant that won’t blossom until next year. 

You may be able to extend the life of your onion bulbs by storing them in a cool dark place for several months during the colder months. Leaving on indirect light or putting it near heating devices can shorten its life expectancy. 

But, most horticulturists advise against this as temperatures below 40 degrees Fahrenheit could ruin your crop for the following year. Others claim that this doesn’t work at all and has caused more problems than anything else, including rotting onion bulbs or increasing pest populations.

Leaving an onion in the ground means that the plant keeps growing over winter and going until its died back in early spring. The bulbous root system at this point can be planted and transplanted successfully. 

Bottom Line

Onions typically do not grow in the ground. Instead, they sprout near the surface of soil and develop into plants. These plants are cultivated by farmers to create large amounts of onion bulbs at a time. 

All one needs to do to avoid planting a new onion is slice off the roots, wrap them in newspaper, and store them in a warm place like an oven or basement for a few weeks.

You can also just buy pre-grown onion bulbs that are ready to be harvested from your local grocery store or big box retailer. We hope that this blog post has helped you learn more about onions and what it takes to grow them.

It’s time to start growing your own!

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Meet Tomas Clayton, a seasoned plant gardener who has been passionate about horticulture since he was a child. Tomas John developed a love for the natural world and a strong appreciation for the beauty of plants while growing up on a farm.

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