How to Grow Onions from Seed to Harvest

You want to grow onions? Great! This article is for you. In fact, I will give you all the information so that you can grow your onions step-by-step from seed to harvest.

Not only that, but I will give you some additional tips at the end of this article to make your growing experience even more successful. Enough talking, let’s go straight into it.

how to grow onions from seed to harvest timeline

Table of Contents

Onion Plant Profile

Size (Height, Spread)6 to 9 inches tall and 3 to 5 inches wide.
ClimateOnions grow best in moderate climatic zones with temperatures between 75 and 85 degrees Fahrenheit.
Sun ExposureOnions grow best in sunny or half-shady environments.
Soil RequirementsOnions prefer rather neutral soil with a pH of 6.5 – 7.
Country of OriginCentral Asia.
Growing DifficultyEasy – Intermediate.
Perennial?No, onions are usually grown as annuals.
When should you start to grow?You should start growing your onions in spring.
Expected Yield & HarvestYou will usually only get one onion per plant.
Time from Seed to Harvest80 to 120 days to grow onions from seed to harvest.
Pests & DiseasesNematodes, Onion Flies, Bulb Rot, Purple Blotch, Downy Mildew, Onion Smut.
What to do with it?Onions can be used for salads, soups, casseroles, dressings and many other things.

What Types and Varieties of Onions can you grow?

You might not know it since you may be quite used to just a small number of onions from your store.

However, there are many different onion varieties you can grow.

I listed the most popular onion growing varieties below.

  • Bunching onions
  • Italian Torpedo
  • Ailsa Craig
  • Walla Walla
  • Candy
  • Patterson
  • Sturon
  • Southport Red Globe
  • Red Burgundy

While I personally prefer growing Patterson onions since they will deliver quite decent yields and you can store the crops for a quite long time, you should make your own experiences and try many different onion varieties.

In fact, if you have never grown onions before, I highly recommend you to just choose different onion varieties for your first onion growing project.

Not only will you be able to harvest many different onions and can figure out which varieties you want to continue to grow in the future, growing different onion varieties can also be quite a lot of fun and it can also be much more interesting to grow various different onion sorts instead of just one.

When should you start to grow Onions?

You can start your growing onions as early as in mid of March. While you also could wait until the end of May, I would suggest you start as soon as possible so that your plants have enough time to grow really big and to develop plenty of crops.

Especially if you are still a beginner, it can take you much longer to grow your onions and if you want to get your onions ripe in time, it is a good idea to start growing your onions early on in the year.

How long does it take to grow Onions from Seed to Harvest?

On average, you should expect that it will take between 80 and 100 days to grow your onions from seed to harvest.

However, while some onion varieties only need 50 days to grow from seed to harvest, others can need up to 120 days.

As you can see, the time you need to grow your onions from seed to harvest can vary quite a bit.

Apart from the onion variety you want to grow, the growing time also greatly depends on many other factors like the climatic zone you live in, the level of experience you have in growing onions and so on.

Hence, there is no definitive answer to this question. However, as mentioned before, as you start early on in the year, you can be sure that your onions will get ripe in time.

Thus, as long as you start early, you will be good to go. Moreover, growing your own onions is also not about rushing through the growth process. In fact, it’s about enjoying the process and not only the actual yield from it.

Hence, make sure that you have a little bit of patience for growing plants so that it will not bother you when it takes a little bit longer than expected to grow your onion plants from seed to harvest.

What is the best Climate to grow Onions?

Most onion varieties are rather tolerant to different climatic zones. In fact, as long as the climate is moderate and not too extreme, it is perfectly doable to grow your own onions.

Hence, as long as you don’t live in too extreme climatic zones, you will be perfectly fine and you don’t have to worry about whether your climatic conditions are suitable to grow onions or not.

What Temperatures do Onions like?

Most onion sorts grow best in moderate to warm temperatures. The best temperature range to grow onions is between 75 and 85 degrees Fahrenheit during the day. However, note that this is just a rough indication.

Even if you live in a region with a little bit colder or hotter climate, you will often be perfectly fine to grow onions as long as the temperatures don’t fall below the freezing mark from June until September.

What do you need to grow Onions?

You don’t need too many things to grow onions. However, there is some equipment you urgently need in order to make your onion growing experience as enjoyable as possible. This includes

What Yield can you expect when you grow Onions at Home?

From each onion plant, you will usually get only one onion out of it.

However, don’t let this discourage you. Since you can plant many onion seedlings on a rather confined space, you can still grow plenty of onion per square feet.

Thus, especially if you have a big garden, you can ensure your whole yearly supply with onions from your own garden if you really want to 😉.

What should you grow with Onions?

If you want to learn more about what plants you should grow with onions, make sure to also check out all the good and bad onion companion plants.

Why should you grow your own Onions?

You might think that it would just be much easier to just buy your onions from the store instead of growing onions in your garden or your balcony.

And you are indeed right. It will be much easier to just get them from the store.

However, in general, if you grow your own vegetables at home, it is not just about the yield. It is about enjoying the process.

In fact, I personally love to grow onions and other vegetables at home since it gives me a feeling of peace and I can also reconnect to natural processes.

Moreover, growing onions can also be quite helpful to reduce our overall stress level.

In fact, especially if you work in a demanding job for long hours every day, chances are that you will often be stressed and need to unplug from your daily life once in a while.

If this is the case, growing onions can greatly help you in this regard since it can give you a nice contrast to your office life and you can also do some physical work once in a while.

In fact, it can be quite nice when you come home from the office and can just sit in your garden and enjoy your plants around you.

Thus, while growing your own onions does not make sense from a monetary and effort standpoint, it can still greatly improve your overall quality of life and you should be into gardening for the process instead of just for the end result.

Growing Onions: Step-by-Step

1. Select a Site for your Onion Plants

I hope that I convinced you that growing onions at home is actually a good idea.

If so, it is now time to select the optimal site for growing your onions.

Do Onions like Sun?

First of all, we have to clarify whether onions like the sun or not.

While onion plants like to have a few hours of sun, they don’t require sunlight all day long and therefore, a healthy mix between sun and shadow will be perfect to grow your onions in an optimal manner.

What are the Soil Requirements of Onions?

Onions are rather tolerant towards soil conditions.

In fact, as long as the soil is rather loose and not too compact, onions will often grow in a healthy manner if you just use potting soil from the store and mix it with the soil from your garden or with your compost you might produce at home.

If you further want to improve the overall conditions to grow your onions, you could also add earthworm castings to the soil.

However, as mentioned before, onions are not too demanding regarding their overall soil conditions and you can do not too much wrong in this regard.

How much Space do Onions need?

Onion plants don’t need to much space. In fact, it will be enough if you provide around one square foot of space for each plant and you are good to go.

Onion plants usually stay rather compact and will also not grow too big. Hence, the size they need is rather limited.

However, keep in mind that one onion plant usually only produces one onion and if you want to get decent yields, you will also have to plant many onion plants.

In turn, this may lead to a state where you have to use plenty of space to grow onions in your garden.

Should you plant Onions in a Pot or in the Garden?

Both options are perfectly fine. Indeed, if you plant onions in a pot, you will be rather flexible regarding the location of where to place the pot since you can change the location of your pot rather easily.

In contrast, if you grow your onions in your garden, you will no longer be able to move your plants once they are established.

However, I still recommend you to grow your onions in your garden since they will simply have much more space to grow and to develop compared to just planting them in a pot.

In fact, while you will only be able to grow a handful of onions in a pot, you can grow dozens or even hundreds of them in your garden, at least if your garden is big enough.

2. Plant Onion Seeds

Now that you know everything you need to know regarding the optimal location for growing your onions, it is time to get into the actual growing process.

Should you buy Onion Seeds or Seedlings?

While you could just get onion seedlings from your local garden center or from the internet, it is in my opinion far more interesting to grow your own seedlings instead.

In fact, especially if you have never grown onions before, you will miss out on plenty of experience if you just get your seedlings from your garden center.

Learning how to grow seedlings is quite important, not only to grow onions but also for several other growing projects.

Hence, make sure to take this extra step so that you can really get the full onion growing experience.

And don’t worry that growing your own seedlings is too complicated.

In fact, it is quite easy if you know what you are doing and I show you exactly how to grow your own seedlings in the following chapters.

Should you buy Onion Seeds or produce Seeds by yourself?

Since onion seeds are won during the flowering process of onions, you will simply not have the opportunity to produce your own seeds if you don’t already have an onion plant at home.

Hence, you will just have to rely on onion seeds from the internet or from your local garden store instead of producing your own seeds.

Sure, after you have successfully grown your own onion plants, you can also produce your own onion seeds.

However, for starting out, just get some onion seeds from a seed company and you are good to go.

How to plant Onion Seeds

Once you got your onion seeds, you are not ready to actually plant your seeds into your growing bed. Just fill your growing bed with potting soil and place your seeds onto the top of the soil.

Make sure that each seed has at least 3 inches of space to each other so that your onion seedlings will have enough space to develop in a healthy manner.

After you placed your onion seeds onto the soil, just cover it with an additional layer of soil of about one inch. And here you go.

You just need to water your seeds in the last step and you planted your onion seeds in a proper manner.

Make sure to also place your growing bed at a bright and warm spot in your home in order to optimize the growing conditions for your seedlings and you are good to go.

How long does it take to see the first Onion Seedlings?

While the first seedlings will become visible to you after around one week, it can take a few weeks until all seedlings will have developed.

Moreover, keep in mind that not all seeds will actually turn into seedlings. In fact, make sure that you plant more seeds than the required number of seedlings you want to get.

For instance, if you want to get 20 onion seedlings, make sure that you plant around 40 onion seeds to reach this goal.

In general, a ratio of 2:1 between seeds and the number of seedlings you want to produce should be just fine.

If you really produce more seedlings than you need, you can just give them away to your friends who will often be quite happy to get this opportunity instead of having to grow their seedlings on their own.

How to protect your Onion Seedlings indoors

Since you will raise your onion seedlings inside your home, you will not have to protect your seedlings too much.

In fact, compared to the outside world, your onion seedlings will be quite safe indoors and no additional protection measures will be needed.

However, in case you have pets, make sure that your pets are not able to reach your onion seedlings since otherwise, you might wake up one day and there may not be any onion seedlings left 😉.

When should you transplant your Onion Seedlings?

There are basically two main criteria that have to be met before actually transplanting your onions to your garden or to a pot outside your four walls.

The first criterion relates to the size of your seedlings. I recommend you to wait until your onion seedlings are at least 5 inches tall before you consider transplanting them outdoors.

If they are too small, they will not be resistant enough and may be too vulnerable to pests and other dangers waiting for them.

The second criterion relates to the overall conditions outdoors. In fact, if the temperature is still not suitable to transplant your onion seedlings, it doesn’t make sense to do so.

In fact, you should not transplant our onion seedlings before the temperature no longer falls below the freezing mark.

Hence, you should wait with transplanting your onion seedlings until they are big enough and the climatic conditions allow you to transplant them outdoors.

If both criteria are met, you also have to prepare your onion growing site before you can actually transplant your seedlings.

In order to prepare your growing site, just dig holes of around one square foot in size and one foot in the vertical into your garden.

After you have dug those holes, it is time to fill those holes with a mix of potting soil and the soil from your garden.

You can also add worm castings or compost to the soil mix to further improve the overall conditions for your seedlings.

After you filled those holes with your loose soil mix, you can just place each seedling into one prepared spot.

Finally, just water your onion seedlings and the hardest part of your whole growing experience lies behind you, congrats 😉.

Alternatively, you can also grow your onions in a pot. You just have to fill your pots with the soil mix mentioned before and you can just transplant your seedlings to your pots after that.

What kind of Protection do Onion Seedlings need outdoor?

Since your onion seedlings will no longer be protected as they were inside your four walls, you now have to take some additional measures to protect them.

One simple but also quite effective way to protect your seedlings is to simply use slug fences.

Not only will they protect your seedlings from snails, they will also protect your seedlings from various other animals in your garden most of the time.

Hence, just use a slug fence to protect your seedlings and you should be good to go.

3. The Onion Growth Process

Every week your onion plants survive, this will be a win for you. In fact, your onion plants will get much bigger and stronger over time and will also become much more resistant.

Thus, after a few additional weeks, you can be pretty sure that your onion plants will really make it if you follow the tips in the next chapters of this article.

Should you prune your Onion Plants?

While pruning can make sense in the growth process of some other plants like tomatoes, it doesn’t make sense for onions at all.

In fact, you would do much more harm than good by pruning your onions and I urge you to just leave your plants alone in this regard. Just let nature do its work and you will be surprised how good the results will actually be in the end.

Do you have to pollinate your Onion Plants by Hand?

You also don’t have to pollinate your onion plants by hand. Since onions will grow below the soil surface, there will actually not be any need to pollinate your onion plants at all.

However, when your onions develop flowers, you can still try to extract seeds from those flowers so that you no longer have to get onion seeds from the store for the next years.

How to stake your Onion Plants

Since onion plants will stay rather compact and their height will be rather limited, there will be no actual need to stake your onion plants.

In fact, you can just let them grow and you will be good to go.

4. The Onion Harvest

Depending on how well you followed the instructions in this article and also depending on your overall level of experience in gardening, you will now see how well you have done over the past months.

When should you harvest your Onions?

You can usually harvest your onions in late summer or early fall, depending on your starting date and also on the onion variety your grow.

There is one sure sign that your onions are ready to harvest.

You just have to look at the necks of your onions. If these necks are soft and the plant material leans sideways, it is time to harvest your onions.

If you see this the first time, you will exactly know what I mean. Just trust your intuition in this regard, I am sure you will figure it out. If you are not quite sure, you can try to harvest one onion.

If it is ready, you can also harvest all the other ones.

If not, just let your onion plants grow for a little bit longer.

Over time, you will get a pretty good feeling regarding when it is really time to harvest your onions.

How to store your Onions?

The best location to store your onions is a dry, dark and cold spot in your home. This may be the basement or other rooms that meet those criteria.

In fact, if you store your onions in a proper manner, they can stay in good shape for many months.

What should you do with your Onions?

Onions are quite versatile and you can use them for many different dishes. In fact, onions are not only perfect for salads, they are also helpful to make delicious sauces.

Opportunities are almost endless and you can just use your onions for every dish you want to.

Apart from the good taste, onions are also quite healthy.

Hence, do your body a favor from time to time and give it some onion.

Chances are that your health will thank you for that later on.

Onion Plant Care Tips

You already got most of the information you need to successfully grow onions.

However, please stick with me since I will give you some additional general information on how to take care of your onion plants.

How often should you irrigate Onions?

Onion plants don’t need too much water. Since they will stay relatively small, they only need to be watered from time to time.

Especially at the beginning, onion seedlings don’t need much water and it will be enough to water them 2 or 3 times a week.

When they get bigger and it gets hotter outside, you want to water your onion plants more.

You can also see when your onion plants need water by having a look at the leaves.

If the leaves begin to hang before harvesting time, it is a clear sign that something is wrong and if you haven’t watered your plants sufficiently, this will likely be the reason that your onion plants don’t feel comfortable.

Hence, just look at the leaves and you will often see if your onion plants need water or not.

At what Time of the Day should you water your Onion Plants?

While most experts claim that watering your onion plants in the morning is best, I honestly haven’t seen any difference.

In fact, in my opinion, you should just water your plants whenever they look like they need it instead of having a fixed watering schedule and a rigid time of the day.

How often should you fertilize your Onion Plants?

In general, onion plants don’t need too much water.

In fact, if you give them sufficient space to grow and prepare a decent soil mix, your onion plants will grow in a decent manner even without having to add additional fertilizer later on.

What kind of Fertilizer should you use for your Onion Plants?

However, if you urgently want to use fertilizer, make sure to use natural fertilizer instead of chemical fertilizer in order to protect our environment.

While you can buy organic fertilizer from the internet or from your local garden center, you can even make your own natural fertilizer from scratch.

In fact, you just need to get some stinging nettles from your nearby forest and put them into a bucket full of cold water.

After a few days, you can remove the plant material and here you go.

You have a simple but yet effective fertilizer that will greatly benefit your onion plants.

Just give them a little bit of the stinging nettle liquid every week and you will be surprised how well your onions will grow.

Should you use Pesticides or Herbicides for Growing Onions?

I would never recommend you to use chemical pesticides or herbicides for your gardening at home.

Although those substances work, they will also decrease populations of helpful insects like bees and instead of using those chemical substances, you should rather use natural alternatives.

In fact, you can even use your stinging nettle liquid you already produced for fertilizing purposes as a natural pesticide as well. You just need to spray it onto your plants and you will be good to go.

In order to remove weeds, just remove them by hand instead of using chemical substances.

As you can see, you don’t need any chemicals for growing onions.

Just stick with natural components and you will be good to go.

If you want to learn more about pest control, also have a look at how to control onion pests and diseases.

What’s left to say?

Not much actually! 😉 If you made it up to this point, you got all the information that is needed to grow onions from seed to harvest.

Now it is on your to really take action and to grow your own onions at home. I hope you like my onion growing guide.

If you do, make sure to share it will your family and friends as well as on social media so that we can inspire more people to grow their own vegetables as well.

If you want to learn even more about growing onions at home, also make sure to check out my growing onions FAQ section.


About the author

My name is Andreas and I’m really passionate about our environment and also about growing plants. In fact, I have grown several different plants over many years. I love to see my own plants grow and always try new things.

In my blog posts, I want to share my experiences with you so that you can become successful in growing various different plants, even if you are still a beginner right now.

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