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How to grow onions from sets – plant in the garden or in containers!
Onions are so easy to grow! If you use a lot of onions in cooking, why not plant a few rows in your vegetable garden? They are one of the easiest vegetables to grow and the only thing you need to do is keep the weeds under control.
Then just add regular watering and the onions will grow nice and big. Here’s how we grow enough onions here to store enough for year round eating.
Another vegetable we grow a lot of is potatoes. If you want to learn how to grow potatoes, head over here!
How to Grow Onions
I always buy onion sets, because growing onions from onion seeds takes much longer. You can certainly do it, but you need to sow the seeds in January and then transplant later into the garden.
Onion sets are just small onion seedlings that can be planted in the garden.
Be sure to choose a variety that works with the climate and day lengths where you live. Long-day onions will need 14 to 15 hours of daylight per day, whereas short-day onions only need about 10.
There are also day-neutral onions which will produce good bulbs regardless of day length.
To plant, I first run a string line. This way I can try to keep my rows straight; after it is in place, I make a furrow using my shovel.
I like to add some well composted manure to the trench before I plant, but you can also use nitrogen fertilizer like these to promote bulb growth.
If you’re using mulch, be sure to keep it a fairly thin layer as this can retain too much moisture and you’ll want to tops of the bulbs to have pure sunlight. If they aren’t able to have fresh air and full sun, this can lead to rot. Good drainage is crucial for healthy onions.
How to Plant Onions
Make sure you seat the onions bulbs into the soil. Don’t just toss them into the trench – they really do need to be seated with the roots down and pointed end up.
I situate my onion plants about 4 inches apart, making sure they are well seated. Then just fill in the trench and water.
I like to plant my rows fairly close together and thin them later as they grow. I think planting vegetables tightly really helps to keep the weeds and leaves down.
It does make it a bit harder to get into the onion patch though, especially in the beginning months. Some people like to leave a lot more room between plants than I do. It just makes for a bit more weeding.
How to Thin Onions
We can get onions planted here in the early Spring. They get planted in May or as soon as I can get into the garden.
Sometimes I can get them planted in late April. Once planted, they will grow all spring and summer and are completely harvested in mid-September.
All growing season long, I thin any onions growing too close together. This way, Graham gets to eat small onions all summer. Meanwhile the remaining onions get to grow a lot bigger.
Harvesting Green Onion
When you see small bulbs, you can snip off a few of the green stalks and use them as green onions, or scallions. Take a stalk from several plants, not ALL of the stalks from one plant.
If you will want lots of green onions all summer long, keep planting sets every few weeks. We can grow large bulbs here; most root crops do very well in the Cariboo.
As the season goes on, you will notice that the onion tops start to turn yellow and fall over. If you are getting into September and the tops are still green, you can speed things up by knocking all the tops down.
Sometimes, we want to get the harvest out of the ground in order to plant fall rye to build the soil through fall and winter, so we knock the tops down.
Also be on the lookout for thrips, which suck sap from onion leaves, as well as other pests like aphids and onion maggots that are naturally attracted to the organic matter. You may have to get help in order to deal with these pests–your local garden center is a good place to start.
Don’t cut the onion tops off, just push the tops over. Then let them dry some more before pulling them from the ground.
When it is time for harvesting, try to do it on a sunny and long day. Long summer days are great for this if the onions are ready by then. Pull the onions, gently brush any dirt off and then leave them in the garden to begin to dry for a few hours.
If you don’t have cool overnight temperatures like we do, you can just leave the onions in the garden for a few days.
We can’t do that here, because we are concerned with even a very light frost falling on them. The onions always get moved before nightfall, just in case.
We cure our onions by tying them in bunches and hanging them from the barn rafters. Here the onions get the benefit of fresh air and wind, but they are under cover.
This way they stay out of the sun. They are also protected from a freak frost, which can happen here in our Zone 3.
We leave them hanging there for two or three weeks. Then, they are brought up to the house and put downstairs.
We do NOT store onions in the Cold Room storage. We find they like slightly warmer temperatures and we also don’t want the smell of onions permeating the other veggies we are storing.
Read more about storing onions for winter here
What you want is a place where the onions will not freeze; around 50 F is a great temperature. You can also make a few onion braids and hang them in your kitchen. They look so pretty!
You can store them in a mesh bag to keep them contained, but don’t keep them in the refrigerator, as this is too damp an environment.
If you use onions in cooking, grow some of your own. Almost free onions are much better than having to pay for them at the grocery store!
Types of Onions
Here’s a list of some varieties of onions that are good to grow in your garden. I’ve found that red onions and yellow onions tend to grow well!
- White Bermuda Onions
- Yellow Granex Onions
- Yellow Sweet Spanish Onions
Questions about Growing Onions
How long do onions take to grow?
Generally, onions take about 150 to 175 days to grow to full maturity. But, remember that you can dig onions while they are growing.
How many onions grow from one bulb?
One onion will grow from one bulb. It’s just that you plant a little onion set and get a full size nice big onion months later.
How deep to plant onions?
Plant onion sets anywhere from 1 1/2 inches to 2 inches deep.
More Posts about Onions
How to Store Onions for Winter – grow and save fresh onions to eat all winter
Make Pickled Onions – try this recipe!
A list of pretty much every Preserving Recipe we have here, from freezing to canning and more!
Want to find out which are The 5 Easiest Vegetables to Grow?
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originally published 2016; updated June 2022