The Garden

5 things you need to know about growing onions

Growing onions

Onions are a staple in just about every kitchen no matter where you live in the world or whatever your cuisine of choice may be. They are the base of most recipes and for good reason! So as a suburban homesteader it only made sense that I set aside a sizeable section of my yard for growing onions of my very own.

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I should point out right at the beginning that there are two main ways to grow onions, from sets or from seeds. Most people grow from sets, but not wanting to be like most people, I grow mine from seeds. There are two reasons I do this; cost and variety. I can get a package of about 300 seeds for $4 or I can get an onion set with 90 onions for $6. This may not seem like a huge difference, but I do NOT currently have enough space for 90 onions. So some would get wasted and I would only have one variety. That said, onion seeds do not have a very long shelf life so you will need to use them up within a year or two. I get mine, like all my other seeds, from Baker Creek Heirloom Seeds.

Growing onions from seeds

By using seeds I can grow multiple types and I only plant what I have space for. I also reduce waste as I can save any leftover seeds for the next year. Some people also claim that onions grown from seeds have better storage potential than those grown from sets. This is because sets are created by growing onions from seeds and then picking them early when they are immature and drying them.

Onions form bulbs in response to temperature and the length of sunlight. There are two many types “short-day onions” and “long-day onions”. The type that will be best suited to your garden will depend on where you live.

Lond Day onions

If you are further north (like me) in southern Canada or the Northern USA you will be best served by choosing the “long-day” varieties. This is due to the fact that during our main growing season our days are much longer than in the winter months. If you try growing these varieties too far south you may find that they do not even create bulbs. Long-day varieties include:

  • Utah yellow sweet Spanish
  • Walla walla
  • Patterson
  • Redwing
  • Sturon

Short-day onions

If you find yourself in the more southern states then you will be better off choosing short-day varieties. They do best with shorter days where they are exposed to shorter amounts of sunlight. Keep in mind that if you try and grow these varieties further north then you will find that they bulb up too fast. Short-day varieties include:

  • Red burgundy
  • White Grano
  • Stuttgarter
  • Southern Belle
  • White Bermuda
Onion seeds

1 – Start them early

Exactly how early you need to start your onions will be dependant on if you have decided to go with seeds or sets. If you have chosen the former then you will need to start your seedlings much earlier than if you chose the latter. I find that using a Seed starting & Harvesting guide really helps to keep me organized and on top of my planting.

If you have chosen the seed route then on average you need to start your onion seeds 8-12 weeks before you need to move them outside. Keeping in mind that they need to go outside about 3-4 weeks before the last frost! So these babies need to be started EARLY. For me in Ontario (Zone 5), that means mid-January. If you are not sure when you’re last frost date is you can look it up HERE (for Canada) and HERE (for the USA).

Onion seedlings

Sadly this is one time that I can’t use my beloved Aerogarden Farm Plus to start seedlings. I really rely on it for just about all my other seedlings, but root vegetables and onions just don’t work for obvious reasons. So instead I need to start them in the dirt. If you are looking for some trays to start your onions (or other seedlings) check out Bootstrap Farmer, they have just about anything you could need! This 72 cell tray is perfect for starting all your onion seedlings.

If you have chosen to go with sets then you will need to wait until the soil is workable in the spring. You will want to plant them outside about 3-4 weeks before the last frost date.

2 – Feed them well

Onions are heavy feeders who like a rich soil that has lots of compost and manure to keep them well-fed and produce good-sized bulbs. Compost can be mixed into the soil as you are getting ready to plant the onions. However, manure should really be applied at the end of the previous season. So if you didn’t add it last year then best to wait until the end of the current growing season and add it for next year’s onions.

They are also quite partial to well-drained soil with a pH of 6.0-7.5. You can also add a good organic fertilizer, they are particularly fond of nitrogen. Onions can be fertilized until the bulbs start to protrude from the ground. Avoid the urge to cover the bulbs back up as they need to emerge above the soil. It is also important that the soil is loose and does not contain heavy clay or rocks which could affect the bulb development.

Watering onions

3 – Water is key

Keep your onions watered but allow for adequate drainage in your soil. Mulching your onions is a great way to help ensure the soil stays damp. The mulch will reduce the amount of watering you need to do. This method should leave them needing no more than 1 inch of water a week (either rainwater or from the hose). More frequent watering is also said to lead to sweeter onions. However, you will want to stop watering them in about August to allow the bulbs to fully mature in preparation for harvesting and storage. I’m planning on adding two rain barrels to my garden this spring so that I can save water and make use of the free stuff falling from the sky.

4 – Give them sun

Onions are sun bunnies for sure! If they could they would spend their days at the beach, so make sure that you plant them where they will get full sun. Make sure that whatever you are planting near them is not going to shade them because they won’t like this at all. They do best when they get 14-16 hours of sunlight.

5 – Don’t crowd them

Lastly, give these guys their space, they need enough room for proper bulb development and won’t thank you if you crowd them. One good way to make sure they are properly spaced and get the most out of the space you have is to use square foot gardening. If you are not sure what this is or how to do it then check out my post Beginners guide to square foot gardening. Another benefit to mulching (other than keeping moisture in the soil) is the fact that it helps avoid weeds. Which is good because onions, like most plants, hate weeds. Even other weeds hate weeds!

UPDATE: So I am conducting an onion experiment this year to challenge this wide-held belief. When I originally wrote this post I was of this same belief, but as with everything gardening it is a constant learning experience. I have since found out about multisowing onions so I am giving that a try this year, you can see the first video below on this topic!

Spanish onions

One last thing that is important to know is how to cure your onions properly before storing them. There is nothing worse than growing a bountiful onion harvest only to find it a leaking pile of goo when you go to use them. So be sure not to skip this very important last step! I will be building an onion drying rack during the summer, in preparation for this year’s harvest so stay tuned for that DIY.

Assuming all goes well you should have a bounty of onions that you can braid until your heart’s content. Not sure how or why to braid onions? Stay tuned for my Onions harvesting and storage guide to find out more! If you grow any red onions then you could also use some of your bounty to make fermented red onions (which are delicious by the way).

Happy growing!

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