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How To Grow Onions From Sets For A Easy Harvest

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Would you like to grow onions in your garden? The easiest way to get started is to grow onions from sets.

HOW TO GROW ONIONS FROM SETS: Would you like to grow your own onions? Onions are so easy to grow from sets if you follow these simple tips. Enjoy harvesting lots of onions from your backyard garden.

The good news is that onions are really easy to grow as long as you follow a few easy gardening steps!

Growing your own onions opens up a world of tastes that you just can’t find at your local grocery store. They also take up very little space so you can grow onions in containers, flower garden borders, or if you have the room plant longer rows in your backyard garden.

Types of Onions

Did you know there are different types of onions?

Oh, I know there are white onions, yellow onions, red onions etc. But that isn’t what I mean.

There are different types of onions that grow better depending on where you live. These can be broken down into 3 types. Long day onions, short day onions, and intermediate also called day neutral onions.

If you have ever grown onions and struggled to get them to form bulbs you may have been growing the wrong type of onions for your area.

See, onions are very sensitive to daylight. Their bullying process is triggered by the amount of daylight you have and the lengthening of your days.

Long Day Onions

These onions are the type we normally grow in our garden in Ontario. Long day onions are best suited to gardeners growing in Northern growing areas.

With long day onions, their bulb formation is triggered when the amount of daylight reaches 14 to 16 hours long. Before this time the plants are putting all of their energy into growing roots and top growth.

This means you will have nice tall onions plants and once the amount of daylight reaches 14 to 16 hours the bulb formation will start and the large onion tops will really start to feed energy into the growing bulb.

If you were to try growing short day onions in your northern garden they would start to bulb up to early in the growing season. Without having the top growth of a mature onion plant to feed the bulb it would be much smaller.

Short Day Onions

Short day onions are grown in Southern areas where there isn’t as much variation in daylight hours as there is in the North.

This type of onion will start to form bulbs earlier in the growing season when the daylight length reaches 10 to 12 hours long.

If you were to try to grow long day onions in a southern garden they would likely not get enough light to trigger the bulb formation to start.

Intermediate (day neutral)

The 3rd type of onions is intermediate also called day neutral onions. These types need 12 to 14 hours of daylight to start to form bulbs. They are not as sensitive to the amount of daylight available and can be grown in both Northern and Southern gardens.

Multiplier Onions

Multiplier onions are also sometimes called potato onions. These are very easy to grow onions that are ideal for small spaces.

You can plant multiplier onions in the spring or fall but a fall planting will give you an earlier start for growth next spring.

They are similar to shallots but grow larger, up to 3 inches in diameter. Unlike most onions, they form clusters of small to medium sized bulbs that are joined together at the base.

Multiplier onions store very well and are perfect to grow if you don’t use many large onions in your cooking. They also make excellent pickling onions.

How To Plant Onions

GROW ONIONS FROM BULBS: How to grow lots of amazing onions in your garden by planting onion bulbs. Learn how to select, plant, care for, harvest and store onions.

When going to plant onions you have a choice of 3 methods. You can plant onions by sets, seed, or transplants.

If you’re going to plant onions very early in the season it’s best to use sets because they will start to grow faster and not need any hardening off or protection to get them started.

If you are wondering what an onion set is, it’s simply a very small onion bulb that was grown close together the previous year on purpose to make small bulbs. These small bulbs are then harvested, dried and sold the next spring as onion sets.

These onion sets are sold in bags or in bulk at most garden centers and farm stores but they can also be ordered online.

Stargazer Perennials Mixed Red, White and Yellow Onion Sets 8 oz | Organic Non-GMO Bulbs - Easy To Grow Onion AssortmentStargazer Perennials Mixed Red, White and Yellow Onion Sets 8 oz | Organic Non-GMO Bulbs – Easy To Grow Onion Assortment

Selecting The Best Onion Sets

The best size of onion set to plant are ones that are 1/2 inch in diameter. You can plant larger ones but they are more likely to bolt. That means that they will flower and go to seed and not make a bulb for you to harvest.

Onions are biannual plants that mean that they will grow the first year and overwinter then start to grow the next year and make seed. This is why onions grown from sets are more likely to bolt in your garden.

But they do give you an earlier start to the season so it’s a trade-off, most of your onion sets will grow and produce nice bulbs just fine.

Planting Onions From Sets

You can plant onions sets out into your garden as soon as the soil has thawed in the spring. Plant the onion sets 1 1/2 inches to 2 inches deep so the top of the bulb is level with the soil. Then space your rows 6 inches apart.

Don’t plant your onion bulbs too deep especially if you have heavy clay soil because it will keep the onions from being able to expand and grow.

How To Grow Onions From Sets

Ok, your onions are all planted. Now here are some easy tips to help you care for your onions as they grow in the summer. It’s not hard just follow these steps to grow amazing onions!

How Much Light Do Onions Need?

Onions grow best when they are planted in a garden that gets full sunlight. You can grow onions in partial shade but they will not grow as large.

It’s good to keep this in mind when planning your garden to make sure your onions are getting as much sunlight as possible and not being shaded by other taller plants.

Watering Onions

Onions are a shallow-rooted plant that needs enough watering to keep the soil evenly moist. Because onions are shallowly rooted they can’t access water that is further down in the soil. They will need 1 inch of water each week, this includes rainfall.

If you’re in a drought or just having much hotter temperatures you will need to increase the amount of water each week.


It’s a good idea to mulch your onions well with straw or wood chips to help retain moisture and reduce weeds. Mulching will reduce how much you need to water each week because the soil won’t dry out as fast.

If you don’t like strong tasting onions you can increase the amount of water you give the plants. Onions that are watered more will not taste as strong because the water dilutes the flavour.

A few weeks before harvesting onions cut back on the watering to help them dry. This will improve how well they store.

Fertilizing Onions

Onions are heavy feeders, this is partly because they are shallow rooted. Onions are only able to take water and nutrients from soil near the surface. Taking care to water and fertilize your onions right will help them grow bigger.

You will need to provide lots of nitrogen for the onions to grow large tops. My favourite way to do this is by adding good compost to the garden before planting onions.

How Often To Fertilize

Then every 2 weeks as the onions are growing you can top dress the plans with more compost or water with compost tea. Adding blood meal to the garden is another organic way to increase nitrogen.

Stop fertilizing with nitrogen once the onion bulbs start to push up from the soil. Also, don’t try to cover the onions with soil at this point because the bulbs need to emerge from the soil to finish growing larger.

Onions also have high requirements for potassium and phosphorus. You can add these to your garden by adding about 6 pounds of wood ashes for each 100 square foot bed.

Easy Ways To Fertilize

We take a relaxed method to adding fertilizers to our garden and simply apply the wood ashes evenly over our entire garden. Since we heat with wood heat it’s a very easy source of fertilizer. You can also add the wood ashes to your compost pile to be mixed and applied that way as well.

If you have a traditional garden you can till the soil amendments in. Since we use a back to eden style, no till garden we lightly layer them on top of the wood chip mulch and the rain quickly washes them under the mulch.

If you don’t have access to wood ashes you can also use blood meal. You would need to add about 1 pound for every 100 square feet of onion beds.

Harvesting and Storing Onions

Onions are very easy to harvest. You can pick them fresh any time of the season once they have reached a size you like.

If you’re growing them for storage onions then you need to wait until most of the tops have flopped over and started to turn yellow. This is a good time to bend over any onion tops that have not yet flopped over.

Wait a few days after bending the tops over to harvest the onions. Gently pull the onions up and wipe off any extra dirt. Lay them out to dry in the sun for a week.

Curing Onions

It’s best to wait until you’re going to have a nice warm, sunny week of weather to harvest your onions. If that’s not possible then you can still harvest them and lay them out in a warm, dry place indoors. Make sure to provide good ventilation so they onions will dry and not rot.

After curing the onions the tops will have turned brown. Gently clean the onion bulbs by wiping off any remaining dirt with your hands. Then trim the tops down to 1 inch in length.

Place your onions in mesh bags or wicker baskets and store them in a cool, dry place. Reusable mesh produce bags like these make storing onions so easy!

Mesh Storage/Produce Bags - 18Mesh Storage/Produce Bags – 18Reusable Produce Drawstring Mesh BagsReusable Produce Drawstring Mesh Bags

See, onions are really an easy vegetable to grow from sets in your garden! Just make sure they aren’t planted too deep and are watered, fertilized and weeded and you will enjoy a good harvest.


Thursday 24th of March 2022

Thanks for this info.