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How to Grow Onions: A Step-by-Step Guide

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Susan has been an online writer for more than 6 years. She enjoys writing about gardening, among many other topics.

This guide will break down step-by-step the process of cultivating and harvesting green onions.

This guide will break down step-by-step the process of cultivating and harvesting green onions.

Why You Should Grow Onions

Onions are hard bulbs in the allium family (which consists of onions, scallions, and leeks) that have a distinct flavour. They are excellent for use in cooking, especially onions fresh from the garden! There are many recipes that you can whip up using onions, and they add a fantastic flavour to any meal, salad, or soup.

In the garden, onions are easy to grow, require little cultivation, and are a great starter vegetable for beginners. Even if you don't have a garden, they can be grown in pots indoors, if you live in the city. If you live in a house with a relatively small garden, you can grow many onions with a small plot.

Health-wise, there are many benefits of eating onions! Here are just a few:

  • Onions contain high amounts of folic acid, vitamins B1 and B6, fiber, calcium, chromium, and vitamin C.
  • They are extremely beneficial to your heart, studies have shown. They thin the blood, lower blood pressure, lower cholesterol, and lower triglycerides.
  • They also contain flavonoids that are antioxidants, which boost your immune system and repel cancer.

“My own remedy is always to eat, just before I step in to bed, a hot roasted onion, if I have a cold.”

— George Washington

Climate and Soil

Onions need a certain soil and climate to grow successfully; however, onions are suited to most climates and soils.

To be more specific, onions love to grow in a sunny spot with plenty of sunlight.

You can grow your onions in any kind of soil, except heavy, dense clay. If you have less fertile soil, add some fertilizer to your soil, or mix in a bag of compost. This will add nutrients to the soil and cause your onions to grow bigger and faster.

You can plant the onions in late autumn or early spring (February, March) and harvest in late spring.

Onions, especially spring onions, are so easy to grow!

Onions, especially spring onions, are so easy to grow!

Soil Preparation

Onions thrive in specially prepared soil, and this will help you to get your onions to grow bigger and tastier.

  • First, make sure your soil is free of weeds and rocks.
  • Loosen the soil with a rake, and mix in half a bag to a full bag of compost.
  • You can add some fertilizer, too, if you wish; this is to help the onions to get a good head start.
  • Loosen the soil again and rake it.
  • Flatten the soil down with your shoe or the head of the rake. Onions love hard soil—the harder the better.
These are the tools you will need.

These are the tools you will need.

What You Will Need

To grow your onions, you will need a few easy-to-find items that can be found in supermarkets or garden centres, or you can even try scavenging in your own garage; you are bound to find some gardening tools in there.

You can grow your onions from seed or onion sets, which are like small bulbs. While I use onion sets in this article, you can use onion seeds if you prefer.

Here is a list of the things you will need:

  • Onion Sets: These can usually be bought very cheaply in garden centres and in large quantities, too. The variety of your onions depends on where you live, but all types of normal onions will do fine.
  • Watering Can: During the summer months, you may need to water your onions.
  • Trowel: This is used for clearing weeds and for planting your onions into the soil.
  • Compost: You can mix some compost into the soil to add nutrients.
  • String: This is used for creating a perfectly straight line when setting the onions.
  • Fertilizer: This can be bought at any garden centre and is also known as 'vegetable feed.' You can use this if you wish, but you will generally get larger onions if you spray them with fertilizer every three to four weeks. Follow the instructions on the fertilizer. If you want to stay organic, avoid spraying the onions with fertilizer or vegetable feed.
  • Hard Rake: A hard rake is used for soil, not for leaves. However, any rake will do. You must rake the soil prior to planting.

Planting Your Onions Using Onion Sets

Now that you have your onion sets and your garden tools, it is time to get planting!

  1. First, weed out the small, soft onion sets from the larger, harder ones. The larger ones are the best to grow. Throw the bad ones away.
  2. Clear any weeds from your garden using a trowel.
  3. Make a straight line using a length of string and make holes in the soil using your trowel about 10 centimetres apart. Each row should be about 25 centimetres apart. Make sure the holes are about 1 inch deep.
  4. Place the onions pointing upwards and make sure that the green shoot is a few millimetres over the soil when covered up.
  5. Cover up the holes and water them.
Onion seeds, which are a lot smaller than  they appear here.

Onion seeds, which are a lot smaller than they appear here.

Planting Your Onions Using Onion Seeds

If you don't want to use onion sets or cannot find any at your local garden centre, you can always use onion seeds. They are a little slower to grow, but they only take about three months. The steps to planting onion seeds are the same:

  1. Rake the soil prior to planting and clear any weeds and rocks in the soil.
  2. Harden the soil with your foot.
  3. Align the piece of string in a straight line.
  4. Dig holes 10 cm apart and make sure each hole is no deeper than 1 inch. Also, if you are making rows of onions, make sure every row is 25 cm apart.
  5. Cover the holes and water.

Cultivation and Pests

You will begin to see the onions developing green shoots after a few days. This is known as germination. The stems will continue to grow, as will the onion. If you live in a dry climate, water well, but do not overwater. You can spray with fertilizer every three to four weeks, but follow manufacturer instructions in you are unsure of the amount and frequency.

Finally, using a hoe, clear any weeds that may arise.

Like most vegetables and flowers, there will always be pests to destroy your onions. There are fungi out there that cause disease:

  • Downy mildew: The stems may appear to turn grey as a fluffy fungus grows on the stems. This fungus is known as Peronospora destructor and causes the stems to die back. To prevent any further damage, remove the affected leaves and stems.
  • Onion neck rot: This disease is caused by the fungus Botrytis allii. You will see a grey-coloured fluffy fungus growing on the head of the onion that will then turn into a black fungus. To avoid this, do not plant onions in the same area every year consecutively. Plant other vegetables such as peas, garlic, potatoes, tomatoes, or beans instead.

Onions in Progress

Onions after three months, almost ready to be harvested.

Onions after three months, almost ready to be harvested.

Harvesting Your Onions

In late August/October, it is time to harvest your onions.

  • When your onions are ready to be harvested, the stems will turn brown, and the onion will be very big.
  • Bend the onion stem slightly to ensure the onion begins to dry out.

After a few days:

  • Loosen the soil around it, and gently pull the onion out of the soil.
  • Clean off any dirt and store in a shed for a few days. You must do this so the onion can develop its flavour.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.


Eric on June 10, 2020:

Should onions top and roots be reduced when going to plant them

Jude on July 14, 2019:

The greenery on my onions is very green but is very floppy should i stake them and tie them or are they OK

Aayush on May 31, 2019:

Thank you

Aamir on December 04, 2018:

In Onion growing article you mistype onion as garlic kindly correct your article.

The Examiner-1 on February 11, 2014:

I was not very explanatory in my last post susi10. I meant to to say the 'gnats came out of the indoor flowers which I grew'. I had a house full of them.

When I said that weather 'deters an outdoor garden' I meant to mention where I live right now.

In NJ I had planted a decent sized flower garden beneath my bird feeders and it grew fine. The only weather problem for the flower garden was winter.


Susan W (author) from The British Isles, Europe on February 11, 2014:

Hi Kevin! Thanks for keeping me posted on how your garden is getting on, I always like to hear from my readers! If you do try, let me know on how they turn out. I will be starting soon too and I will be adding pictures to this as soon as they get planted. I agree, weather always deters an outdoor garden. Last year I planted seeds straight into the ground outdoors and they never germinated. I will have a lot more success with germinating them indoors and then transplanting outdoors. Anyway...thanks again and good luck. Keep me posted!

The Examiner-1 on February 08, 2014:

Hi susi10,

I may grow them indoors for now, if I can find the time. I just hope that they do not attract insects such as the flowers that I had previously.

Something like gnats come out of those.

The weather deters an outdoor garden - anytime of the year. Anyway, that was a very good explanation with good photos.


Susan W (author) from The British Isles, Europe on February 07, 2014:

Hi Patsy!

Thank you for the read and for your great comments. It is nice to get such positive comments from a fellow gardener. I am ready to get in the garden too, I will be starting soon. I am planning on growing onions, garlic, peas, beans and potatoes this year. Looking forward to it!

Patsy Bell Hobson from zone 6a, Southeast Missouri, USA on February 06, 2014:

Lots of good information. Voted up and useful. Will Pin it. I'm ready to get in the garden!

Raitu Disong on July 16, 2013:

You are welcome!

She sure will find this useful!.. thanks again

Susan W (author) from The British Isles, Europe on July 16, 2013:

Hi Raitu,

Thanks for reading, I love onions too, they are so flavoursome. Thanks for showing this to your mom, I am sure she will find this useful!

Raitu Disong on July 16, 2013:

I love onions!

My mom loves to grow new crops. I am going to show this to her.

Very useful hub!

Susan W (author) from The British Isles, Europe on July 01, 2013:

Hi BWD316,

Thanks for reading and the great comment! Onions are very easy to grow, try growing them next spring! Onions are definitely a 'must-grow' by all means.

Brian Dooling from Connecticut on June 30, 2013:

As a strong believer in growing at least some of your own food, i've always wanted to grow onions in my garden. Thanks to your hub I realize it's not as difficult as I was expecting! thanks for the information! #happy2years

Susan W (author) from The British Isles, Europe on June 21, 2013:

Hi The Examiner-1!

Thanks for reading my hub and its great to see you. I am glad that you found it interesting and useful, I hope it will help many people in the future.

I'm sorry, I should have clarified which rake I meant, I will adjust that. Thank you for pointing that out to me!

The Examiner-1 on June 21, 2013:

That was interesting to read, very informative for those who do not know how. I used to grow flowers for birds, and maybe some vegetables at a different part of that yard, I do not remember. Unfortunately I do not have time to do so these days.

By the way, I do not know what you use but we use a soft rake for leaves so when you first mention a rake you might want to add the word hard. It is up to you.

Susan W (author) from The British Isles, Europe on June 21, 2013:

Hi Peggy!

Thank you for reading my hub, I am delighted! Harvesting onions while they are still small is a great idea, they have more of a spring onion flavour and have a fresh taste. Sometimes, if I don't have enough room for big onions, I thin out some of them, I harvest a few while they are still small in Spring. That way, I can eat some scallions too.

Susan W (author) from The British Isles, Europe on June 21, 2013:

Hi KDeus,

I'm so glad to see you, and thank you for reading! Its great to hear that you will plant a garden in the fall, you'll have plenty of home grown produce! I'm sure you will enjoy planting onions in the fall, they are easy enough to grow. Thanks again for visiting!

Susan W (author) from The British Isles, Europe on June 21, 2013:

Hi queerlyobscure!

Thank you for reading my hub about growing onions, I'm so happy that you liked it! Yes, I agree, you would definitely save a small fortune growing onions, even setting a small patch will give you enough onions for you for a whole year. Neat!

Peggy Woods from Houston, Texas on June 21, 2013:

I have grown onions from onion sets and generally harvest them while still small. We use lots of onions and garlic in our cooking. Love it and like you mentioned, it is so good for one's health. Voted up and useful.

Keely Deuschle from Florida on June 21, 2013:

Excellent article! I grew onions from seed in my raised bed garden last year and it was the first time growing them. I was so busy in the beginning of the year that I never started my garden for this year as we have to start it really early here in Florida. Once the weather gets a little cooler here in the fall, I'm going to plant some, including more onions! Voted up!

Cecil Wilde from Melbourne, Australia on June 21, 2013:

Aaah I'd love to grow my own onions. I'd save a small fortune. Great hub!