How To Grow Big Onions – From Plant To Harvest (Video)
Learn how to grow big onions in your garden with this step by step guide showing you all you need to know from planting through harvest and even storage. Learning when and how to plant onions has a lot to do with how big they get, and how many pounds you’ll have at harvest time. Onions are fairly easy to grow providing they have rich soil and you keep them free from weeds. Onions aren’t bothered by many pests either. Growing giant onions is also an important step in growing the food to fill your pantry.

Pantry Staple
Onions are a staple food for our family as they are the basis for a lot of meals especially during the wintertime. We use them in soups and stews, and in a lot of our canning recipes. I also like to put them in fried potatoes, make sourdough onions rings, or add a slice of raw onion on hamburgers. There’s probably as many ways to use onions in food as there is potatoes. You can literally eat them everyday. We also use them medicinally at times, so they are a really great vegetable to have on hand.
Why I Love Growing Onions
I love growing onions because after pulling them in the fall, they can be stored for many months in a cool dark place like my homestead pantry without having to be preserved. So much of what we grow has to be preserved in some way, and onions can be kept for quite awhile without any special storage preparation other than curing. We do dehydrate some onions and freeze some as well, especially as the winter goes on. But for the most part we store them just like they are when they come out of the ground.

Plant In Early Spring
Onions like to grow when it is cool outside, so it’s a good idea to plant them in the early spring. They can even handle a hard freeze. I’ve had them survive temperatures as low as 20 degrees farenheight. You can find out when it’s safe to plant them in your growing zone by looking up your last frost date on the Old Farmers Almanac website. Then put that last frost date into a free garden planning tool called Seedtime. This will show you when it is best to plant each crop outdoors, and whether they should be started indoors first, or direct seeded into the garden.
Onions can be started indoors from seed, or planted directly into the garden from sets or plants. The great thing about onions is that they can handle a light frost. So you can plant them out into the garden earlier than some other crops like tomatoes or cucumbers.

Day Length
To grow large onions, there is something you must understand about how onions grow. Onions depend on length of daylight to tell them when to start producing their bulb. When planted into the garden, they first start growing their leaves, and they continue putting all of their energy into growing their leaves until the daylight gets to be a certain length. Then the onions start putting more energy into bulbs than leaves. As a general rule, they produce one ring in their bulb for every set of leaves they grew. So the more leaves they grow, the larger the size of the onion bulb will be. This is why you have to plant onions really early in the spring if you want them to get really big, because they need as much time as possible to grow lots of leaves before the days get long in June.
Different Onion Varieties
Onion varieties are separated into three groups based on day length, and it’s important that you purchase the right onions for your growing region. The closer you are to the equator, the more your days and nights are equal in length. The farther away you are from the equator, the longer your days in the summertime, and the shorter your nights.
The three groups are:
- Long-Day Onions – take 14-16 hours of daylight to bulb out (which usually happens in late June for me), and grow best in the northern half of the United States, or in areas that get days that long during the summertime.
- Intermediate Day Onions (day-neutral) – take 10-12 hours of daylight to bulb out, and are generally best for the middle part of the United States
- Short-Day Onions – these onions are best grown in the southern United States or areas closer to the equator.
Of course if you live in other parts of the world, you can apply the same information about daylight to where you are.
It is important to note that if you live in a warmer climate, and plan to grow your onions over the winter, that you may need to get a shorter day onion variety in order to have nice, big onions. It will all depend on your average day length in the winter.

Best Methods For Starting Onions
There are three methods for starting onions. Listed below each method are the pro’s and con’s for each:
1. Onion Seeds
Onion seeds can be started indoors under lights or in a greenhouse
Pros
- They are fairly inexpensive
- Lots of varieties to choose from
Cons
- They take up valuable space on your seed starting racks for a long time, because they have to be started so early, and are slow growing
- It can be difficult to get them to germinate
- Transplanting them into the garden is a tedious task because even after growing indoors for 12 weeks, they will still be super tiny.
- Because they are still very tiny when planted out into the garden, it takes them a long time to reach maturity, and they usually aren’t as big.
2. Onion Sets
Onion sets are small dormant onion bulbs that can be purchased from a nursery or seed catalog, and planted directly into the garden.
Pros
- Onion sets are the easiest to plant because they are about the size of a quarter, and can easily be pushed right under the soil in the early spring. These are a great thing for kids to plant.
- They sprout and grow easily, using the energy they have stored in their mini bulb.
- Easy for kids to plant and grow. In some cases onion sets are the best option. As long as you don’t need really big onions at the end of the season.
Cons
- Onion sets are grown by seed companies and are basically little tiny onions that were grown to produce small bulbs. They were then harvested, dried and stored over winter. Then packaged and distributed to seed companies and nurseries to be sold. Onions are bi-annuals, meaning they don’t produce seed until their second year of growing. When planting onion sets you are growing an onion in it’s second year of growth. So they naturally want to put all of their energy into producing flowers and seeds instead of large bulbs. If you’ve ever struggled with your onions going to seed when they were still really small, this is why. As a general rule, if you plant onion sets you will get smaller onions when growing.
- Sometimes the quality of the sets isn’t that great depending on how they were stored over the winter, and so they don’t all sprout.
3. Onion Transplants
Onion transplants are started in the winter by a nursery, and can be ordered from a seed catalog to be shipped to you in early spring. They are generally a lot bigger than onion plants you start yourself and can be directly planted into the garden.

Pros
- They are very easy to plant compared to onions started from seed. I can plant over 1,000 onion plants in less than 90 minutes.
- They are actually mini plants that come bare root and are shipped directly to you.
- You don’t have to worry about starting them yourself or taking up valuable space, time and energy from your indoor seed starting setup
- If planted in early spring, they acclimate well with hardly any transplant shock
- You can choose when to have them shipped to you. Sometimes the seed company will ship them based on your weather, so you can get them planted as early in the spring as possible.
- Because they are bare-root plants still in their first growing season, they will naturally put more energy into the bulb formation rather than seeds
- This is the method to follow if you want the biggest onions. It’s not uncommon to get 1 to 2 pound onions when planting them this way.
Cons
- They cost more money than the other options, but produce a more reliable harvest.
- Seed companies can sell out of these relatively fast, so it’s important to order them early in the season.

I’ve been using method #3 and planting onion plants for several years now. I’ve never had larger onions. I’m never going back to growing onions any other way if I can help it.
FAQ:
Where Can I Purchase Onion Seeds Or Plants?
You can purchase onion seeds from seed catalogs like Johnny’s Seeds, Berlin Seeds or from True Leaf Market.
What is the trick to growing onions?
Onions prefer well drained fertile soil. They need to be watered 2 or 3 times a week on average. The most important thing to remember about growing onions is to plant them early because they are daylength sensitive. Also, look for varieties that are either good for fresh eating or storage, depending on your needs. I like to grow several varieties so we have onions throughout the season and into the winter.
What Kinds of Onions Are Best For Storing?
It’s a good idea to grow some onions for fresh eating and some varieties that will store well. In my experience, the best storage onions are the red wing variety. Another great storage variety is Patterson.

Can I Cut The Tops Off My Onions While They Are Still Growing?
Yes, you can trim the tops of your onions anytime, and it won’t hurt the growth of the plants. In fact, you should trim them back if you start your own seeds indoors. It will help make stronger healthier plants. You can just trim them scissors. I don’t usually trim mine back when they’re growing in the garden. However, when a few of the onion tops start to fall over, it tells me they are bulbing out and will be ready for harvest soon. I then try to gently lay the tops over on all of the onions to they will finish bulbing out and be ready at about the same time.
When To Plant Onions?
This will vary based on your growing season and where you live. I rely on a free gardening app called Seedtime to tell me when to seed or plant all of my crops including onions. You can check it out here. Onions can germinate in cold soil temperatures as low as 35 to 40 degrees, but they grow best in temperatures closer to 60 or 70 degrees. It’s important to start them early so they can get acclimated to their growing environment and be ready to really grow fast as the weather warms up.

What Is The Best Spacing For Onions?
Onions should be planted about 4 to 6 inches apart. You can also plant a group of 4 of them every 12 inches and that will still give them enough soil nutrients to grow. They will just push each other apart as they grow.
Free plant spacing chart for growing on 30 inch wide beds
What Is The Best Way To Water Onions?
I like to water my garden using a drip irrigation system, but you can water it with a sprinkler as well. Onions like about 1 inch of water per week. If you reach your hand down into the soil and there is moisture several inches down, then they probably don’t need watered. Making the roots grow deeper in search of water will create a healthier, more robust plant.
Where To Plant Onions In The Garden?
Onions prefer to grow in full sun, in loose fertile well-drained, soil. They prefer a soil PH of 6.0 to 7.0 but are widely adaptable and will grow almost anywhere. Onions are heavy feeders, so they grow best in a rich, well amended soil. It is best if the soil has good drainage and a lot of organic matter like compost in it as well. To learn more about how I test my soil, click here.

How To Keep Weeds Out Of Your Onions?
Keeping onions weed free is really important for them to be able to have full access to the soil nutrients and sunlight without any competition. I have started growing my onions on fabric (which you will see demonstrated in the video below). It has helped me keep the weeds out of my onions without having to spend time weeding on a weekly basis. If you are not going to grow on fabric, I suggest you set up a weekly cultivating schedule, and use a collinear hoe or similar tool to keep the weeds out of your onions.

Best Onion Companion Plants Are:
- Brassicas
- Carrots
- Beets
- Strawberries
- Tomatoes
- Swiss Chard
- Radishes
- Herbs
Worst Potato Companion Plants Are:
- Beans
- Peas
- Garlic
How Many Onions Should I Plant?
It is a good idea to think of how many times per week you would eat onions if you had them readily available. We use them as a base for so many meals, that I figure our family eats 1 or 2 onions per day. Something else to consider is where you will store your onions and how long they will last before starting to go bad. If you have a root cellar, you can store your onions for up to a year if it is cool and dark. For my family of seven, I plant about 600 onions per year. We also use quite a few onions during canning season for spaghetti sauce and canned vegetable soup.

What Different Types Of Onions Should I Plant?
It’s a good idea to plant at least one variety of onions that is good for storing. Some onions, like walla walla, are great to eat fresh, but they don’t store very long in the pantry. I like to plant walla walla and candy onions for fresh eating, and also some varieties like redwing and patterson for storing through the winter. There are many varieties to choose from, so have fun picking a couple to try, but make sure you have at least one variety that will store well.
How To Preserve Onions?
If your onions start to get soft in storage, you can dice them up and dehydrate them at 170 degrees on a baking sheet in your oven, or for a few hours in a dehydrator. These will be like onion flakes, or you can blend them up to make your own onion powder.
You can also saute them for just a couple of minutes, and then freeze them in an airtight container for up to 6 months. Sauteing them first will keep them from making everything in your freezer taste like onions. You can also put a whole bunch of onions into a roaster or crockpot, cook until just starting to soften and then freeze.
You can also make french onion soup and can it.
How To Start Onions From Seeds
If you choose to start your own onions from seed, I would suggest that you start them indoors. Here is a link to my inexpensive DIY plant starting racks. Just put 1 to 2 inches of loose soil in a tray and dampen the soil. Sprinkle your onion seeds evenly across the soil surface. I usually put about 1,000 seeds per 10 inch x 20 inch tray. They have to be planted thickly, and keep in mind they won’t all sprout most likely. Give them a good soaking, and cover with another tray turned upside down. Leave in a cool dark place until they germinate. You shouldn’t have to water them again until they germinate, but you can if they seem to be drying out on top.
Once they germinate, water them and place them under grow lights. Keep the tops of the plants 1 to 2 inches away from the lights. Keep them moist and allow them to grow, adjusting the light height as necessary. Trim the tops with scissors if they get too tall, this will help create healthier, more robust plants. Transplant out into the garden in early spring.
How To Direct Seed Onions
I’ve also heard of people in warmer climates, just planting onion seeds directly into their gardens in late winter and letting them germinate whenever they are ready and as the soil warms up. I’ve not had experience with that, because I grow in Nebraska in zone 4B and some of harshest winter weather and snowstorms are in March or April.
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Landscape fabric, optional
Propane torch – only if using landscape fabric
Onion plants – can be ordered different places, but I prefer Johnny’s Seeds or Berlin Seeds
How To Plant Onions In The Garden
Lay down your landscape fabric and burn holes in it for the onions to grow in. (Optional) If you’re not using landscape fabric, just mark out your rows using a stringline, and start planting.
For onion plants:
Make a hole in the soil and gently stick the onion in the hole. Push the dirt up next to the roots so they can get good contact with the soil.

For onion sets:
Just push the onion sets into the soil with your thumb every 6” or so. As a general rule, you want to cover the seed (in this case the set) with the same amount of soil as the diameter of the seed. So for onion sets, you’ll push them about an inch under the soil.
Plant In Beds
I do most of my growing on 30 inch wide beds, which is what I recommend in my garden planning tutorial. This is a better use of your space than if you are planting in rows. I suggest putting 9 inches of space between your onion rows, and planting 3 rows per bed. If you plant your onions 4 inches apart in row, you can get 450 onion plants in a 50’ long bed. That is usually enough onions for the average-sized family for the year. Occasionally, I have put in a wider bed with more rows in it, and it’s worked out just fine. It’s just a little harder to weed the middle of the bed, because you have to reach it from the outside edge of the bed (see video below for a fuller bed of onions).

Keep Moist
Keep the soil moist until the onions start to grow. This can take a week or two depending on your soil temperature and weather conditions. I will often set up a gentle sprinkler over my onions to make sure they’re getting the water they need until their shallow root systems are more established. Once they are sprouting new growth, it’s fine to just water with a drip line.
Water and Weed
Give your onions about 1” of water per week. If it’s really hot, they might need more, but be careful not to overwater your garden. Cultivate or weed once a week, and the weeds will be easy to keep up with. If using the fabric, I typically only have to weed them about twice during the season, because eventually the onions get big enough that they grow up and shade out the weeds.
When the onions start to bulb out, you’ll want to remove the soil from around the onion bulbs, so that just the roots stay in the soil. This is sometimes called “spooning the onions”, because depending on the consistency of your soil, you may have to use a spoon to pull the soil away from the base of the onions. My soil is loose enough I can usually do it by hand, and usually most of the soil pulls away from the bulb as I’m doing my final weeding of the onions.

How To Harvest Your Onions
When the onion tops start to fall over in late fall, that means they are almost done growing. You can allow them to all fall over on their own, or if you want them to all be ready to harvest at the same time, you can knock the tops of the remaining onions down. Once the stem starts to get smaller next to the onion, it means they are starting to dry up. This is the time to harvest them. To harvest, just pull up the onions, being sure to keep the storage onions separate from the non-storage onions, so you’ll know what onions to use first. You’re also going to want to cure your onions, so pay attention to the weather and try to harvest them right before a dry windy spell.

How to cure your onions.
It is important to dry and cure your onions so they will keep for a long time. Lay them out in a dry spot out of direct sunlight and rain. I like to lay mine on my front porch out of direct sunlight, and let the warm fall winds cure them. You can store them in a mesh bag and hang them in your pantry, or you can braid them and hang them up. It’s important to note that while onion plants can handle some frost in the springtime, the onion bulbs that you plan to store cannot handle any frost. So keep them dry and allow them to cure protected from cold temperatures.

How To Braid Onions
When your onions are freshly harvested, and the stems are still green, you can lay three onions over top of each other, intertwining the stems close to the onion bulbs. Then begin braiding the stems, and adding new onions to the braid as you go. It is very similar to french braiding hair. (See video below). Allow the onions to finish curing outdoors, and then hang in a cool dry place for the winter. I like to keep some hanging near my kitchen for decor and so I have easy access to them while cooking too.

And that’s all their is to know about growing onions. Onions are fun, easy and rewarding to grow, and growing a lot of them gives you a greater sense of food security for the coming winter. Growing onions will also make a big dent in your grocery bill, not to mention that they are healthier for you than store-bought onions as well.

I hope you try growing your own onions, and let me know in the comments below which varieties you’re growing and any questions you may have.
How To Grow Big Onions

Learn how to grow big onions in your garden with this step by step guide showing you all you need to know from planting through harvest and even storage. Learning when and how to plant onions has a lot to do with how big they get, and how many pounds you’ll have at harvest time. Onions are fairly easy to grow providing they have rich soil and you keep them free from weeds. Onions aren't bothered by many pests either. Growing giant onions is also an important step in growing the food to fill your pantry.
Materials
- Landscape Fabric, optional
- Drip Line
- Onion Plants
Tools
- Propane Torch, (only if using fabric
Instructions
Lay down your landscape fabric and burn holes in it for the onions to grow in. (Optional) If you’re not using landscape fabric, just mark out your rows using a stringline, and start planting.
For onion plants:
Make a hole in the soil and gently stick the onion in the hole. Push the dirt up next to the roots so they can get good contact with the soil.
For onion sets:
Just push the onion sets into the soil with your thumb every 6” or so. As a general rule, you want to cover the seed (in this case the set) with the same amount of soil as the diameter of the seed. So for onion sets, you’ll push them about an inch under the soil.
Plant In Beds
I do most of my growing on 30 inch wide beds, which is what I recommend in my garden planning tutorial. This is a better use of your space than if you are planting in rows. I suggest putting 9 inches of space between your onion rows, and planting 3 rows per bed. If you plant your onions 4 inches apart in row, you can get 450 onion plants in a 50’ long bed. That is usually enough onions for the average-sized family for the year. Occasionally, I have put in a wider bed with more rows in it, and it’s worked out just fine. It’s just a little harder to weed the middle of the bed, because you have to reach it from the outside edge of the bed (see video below for a fuller bed of onions).
Keep Moist
Keep the soil moist until the onions start to grow. This can take a week or two depending on your soil temperature and weather conditions. I will often set up a gentle sprinkler over my onions to make sure they’re getting the water they need until their shallow root systems are more established. Once they are sprouting new growth, it’s fine to just water with a drip line.
Water and Weed
Give your onions about 1” of water per week. If it’s really hot, they might need more, but be careful not to overwater your garden. Cultivate or weed once a week, and the weeds will be easy to keep up with. If using the fabric, I typically only have to weed them about twice during the season, because eventually the onions get big enough that they grow up and shade out the weeds.
When the onions start to bulb out, you'll want to remove the soil from around the onion bulbs, so that just the roots stay in the soil. This is sometimes called "spooning the onions", because depending on the consistency of your soil, you may have to use a spoon to pull the soil away from the base of the onions. My soil is loose enough I can usually do it by hand, and usually most of the soil pulls away from the bulb as I'm doing my final weeding of the onions.
How To Harvest Your Onions
When the onion tops start to fall over in late fall, that means they are almost done growing. You can allow them to all fall over on their own, or if you want them to all be ready to harvest at the same time, you can knock the tops of the remaining onions down. Once the stem starts to get smaller next to the onion, it means they are starting to dry up. This is the time to harvest them. To harvest, just pull up the onions, being sure to keep the storage onions separate from the non-storage onions, so you’ll know what onions to use first. You’re also going to want to cure your onions, so pay attention to the weather and try to harvest them right before a dry windy spell.
How to cure your onions.
It is important to dry and cure your onions so they will keep for a long time. Lay them out in a dry spot out of direct sunlight and rain. I like to lay mine on my front porch out of direct sunlight, and let the warm fall winds cure them. You can store them in a mesh bag and hang them in your pantry, or you can braid them and hang them up. It's important to note that while onion plants can handle some frost in the springtime, the onion bulbs that you plan to store cannot handle any frost. So keep them dry and allow them to cure protected from cold temperatures.
How To Braid Onions
When your onions are freshly harvested, and the stems are still green, you can lay three onions over top of each other, intertwining the stems close to the onion bulbs. Then begin braiding the stems, and adding new onions to the braid as you go. It is very similar to french braiding hair. (See video below). Allow the onions to finish curing outdoors, and then hang in a cool dry place for the winter. I like to keep some hanging near my kitchen for decor and so I have easy access to them while cooking too.
And that’s all their is to know about growing onions. Onions are fun, easy and rewarding to grow, and growing a lot of them gives you a greater sense of food security for the coming winter. Growing onions will also make a big dent in your grocery bill, not to mention that they are healthier for you than store-bought onions as well.