How to Grow Onions from Seed in 7 Easy-to-Follow Steps

Did you know that onions were once so valuable that they were used as a form of currency?

Or did you know that it was believed you could place a sliced onion in a jar during cold and flu season, and the onion would absorb the germs to keep you from getting sick?

Also, what about the fact that onions are said to help battle osteoporosis?

Wow! This vegetable seems to have many important uses that could be beneficial to most people. So why wouldn’t you want to grow your own to have on hand all year round?

Well, after you read this post, you’ll be able to raise a lot of onions for very little money and have as many on hand as you need for many different purposes.

How to Start Onions From Seed:

You’ll need:

  • Onion seeds
  • 4×6 containers
  • Seed starting mix

1. Why Seeds?

When a lot of people plant onions, they don’t start their own seeds. In fact, they order what we call ‘sets.’ They look like tiny onions when in reality, that is basically what they are. They are onion bulbs.

Now, a lot of people will tell you this is the way to go for simplicity's sake. That is what I was told when I first began growing onions.

However, I noticed that every year I grew them, the onions would ‘bolt’ before I ever had a decent sized onion. Bolt means that the top of the onion would just grow rapidly and go to seed, so I could plant more onions.

So I began asking local farmers in my area what they do to grow onions. I was stunned when most told me that they started them from seed. The reason being is that the ‘sets’ that you buy are usually the second year plants. This would explain why they were bolting in my garden.

From then on, I’ve stuck to growing my onions from seed and have been very satisfied.

But there are other benefits to growing your onions from seed as well. You also get more variety. It is much easier to find different varieties of onion seeds than to find different types of onion sets.

So if you’d like to grow a wide array of different types of onions, then you’ll be happy with how much easier that can be if you start them from seed.

2. Sow the Seeds

Now that we’ve established why I prefer to start my onions from seeds instead of ‘sets’ or bulbs let's get busy talking about how we start those seeds.

To begin, you’ll need a 4×6 pan. I usually use an aluminum pan similar to what you would use to make a lasagna in.

Then you’ll want to fill the pan about halfway with seed starting mix. I prefer to purchase seed starting mix just for simplicity sake, but you can also make it yourself if you prefer.

Once your pan is filled halfway, you’ll want to plant two rows of onion seeds in the pan. Then you’ll want to cover them the rest of the way with more seed starting mix. You want the pan to be mainly full.

Now that you’ve got your seeds in place, it is time to move on to creating the proper setting for growth.

3. Create the Right Environment

via Savvy Gardening

So we all know that seeds have to have a good environment to germinate. This is the environment that encourages the seed to sprout and no longer lay dormant.

Well, you have to create this environment for your seeds. You’ll want to place your pan with the seeds in a location where they can be warm without being made too hot.

So if you have a wood stove or a fireplace that you use regularly, then you might want to place them a few feet from it for them to get heat from it.

Also, you can place the pan on top of your fridge where it is nice and warm to encourage germination.

Finally, if you just don’t have the set-up to germinate your seeds with the other methods provided, then you might want to consider a seed starter heat mat. It is a mat that fits under your pan of seeds that will produce warmth. You can purchase a seed starter heat mat, or you can make one yourself.

Once your seeds are in a happy, warm location, then you’ll need just to let them be. You’ll want to make sure that the soil stays moist by using a spray bottle of water and misting the ground when it is dry.

Finally, you’ll need to be patient as the seeds can take around two weeks for them to germinate.

4. Give Them a Trim

via MOFGA.org

Once your seeds have germinated, you’ll realize this because you’ll see little sprouts of life sticking up out of the soil.

So you’ll need to be patient and allow the onions to grow. You will want to continue misting the soil as needed.

Again, you don’t want to overwater, so check your soil daily. When you stick your finger in the ground and it is dry, then you’ll know it is time to mist the soil again. Overwatering young seeds are as big of a threat to them as not watering enough.

However, once you see that your onions have a sprout on them that stands about 4 or 5 inches tall, you’ll know it is time for a trim. You’ll want to use kitchen scissors to trim the sprout back to a more manageable size.

In our experience, we usually cut it back to about 2 inches or so. You don’t want to cut the onion back down to the dirt, but you just don’t want them to look like a troll with a crazy hairstyle either.

Once you’ve trimmed your onions, you’ll need to keep nourishing them and caring for them until it is time to plant.

5. Harden Off and Planting

Before you can introduce your onion sprouts to the cold, cruel world, you’ll need to begin by hardening them off. This is a good way to get them acclimated to the outdoor temperatures and help them to have greater success when planted.

So when your plants are about 2-4 weeks from planting, then you’ll want to start setting them outside. You’ll begin by putting them out for about 20 minutes and building up to a couple of hours (or more.)

Depending on where you live you’ll want to plant your onions in late April or May. Whenever the ground has thawed, and the last frost is done, you should be good to go. When planting onions, you dig little holes for them.

So you’ll want to leave about six inches of space between each planting location. When you have your holes dug, you’ll do just as you would if you had purchased ‘sets’ of onions. You’ll place 4 of each onion sprout in a hole.

Then you’ll cover the root of the onions and have little sprigs of onion sticking out of the ground. You’ll want to be sure to water the onions once they have been planted to give them a warm welcome to their new home.

6. Take Care of Them

via Harvest to Table

Once your onions are in the ground and thriving, you’ll need to do a few things to care for them. You’ll want to make sure that you keep the soil watered where they are. Every plant needs water. That is just a safe rule of thumb.

But the biggest thing you need to do is to keep the weeds under control around your onions. Your onion will try to compete for nutrients with the weeds and sadly, will lose out.

So if you want large homegrown onions, then you need to keep the weeds out of their turf. You’ll just need to be careful not to upset the bulb of the onion when weeding.

Which means you’ll want to use your hand to gently pull the weeds out from around and between your onions. If you do this, then your onions will hopefully thrive.

7. Harvest and Store

Okay, so you’ve started your onions from seed. You made it through the germination process, and they sprouted. You cared for them, hardened the sprouts off, and planted them successfully.

Now, you’ve managed to keep them watered, the weeds down, and have done all you can to produce a healthy crop of onions.

So now is the moment of truth. It is time to harvest them. You have different parts of the onion to collect at different times, so you’ll need to take note of this.

First, you can harvest the green sprouts on top of the onion. When they are around six inches in height, it is time to use your kitchen scissors and collect those. The taller they get, the stronger or more robust flavor they get as well.

So if you want a mild onion flavoring, you’re better off harvesting at the 6-inch height.

Next, you’ll want to check your calendar for when you planted your onions. Onions take anywhere from 100 days to 120 days to be ready to harvest. At this time, you’ll want to see if you’ve had any onions that have ‘bolted.’ We discussed this earlier how some onions will go to seed.

If you find this, you’ll need to cut the top of the onion off and dig the onion out of the ground (gently), so it can be used immediately.

Finally, between day 100 and day 120 you’ll need to pick a cool morning to harvest your onions. You can either gently pull the onion out of the ground, or you can gently dig the onion out of the ground with your gardening tools if the ground is harder.

Then it is time to cure your onions. You’ll want to lay them out on a flat surface where they will get lots of air flow. You can choose to leave them lying on a table in a shed or storage area that gets plenty of air. You’ll want to leave them there for about three weeks. You’ll know they are done curing when the outer skin of the onion is crispy, and the stem is dried.

From there, you’ll want to cut the tops off of the onions where you leave only an inch of the stem.

Then store them in a basket that provides good air flow. Your onions should last around three months. Remember to store them where it is cooler. If there is too much warmth, then mold could form and will ruin your harvest and hard work.

Well, you know now how to start your onions from seed and carry them through to storing them for later use.

So I’d like to hear from you. Do you prefer to start your onions from ‘sets’ or seeds? Why?

We love hearing your thoughts, so share them with us! Just drop your comments in the space provided below.

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