Onions – Things to Consider Before You Order

You don’t really have to know a lot to be successful with onions. I can state that with authority because I was successful growing anywhere from 1,000 to 3,000 onions each year for more than 3 decades and I didn’t know much. See my post Growing Onions – Top 3 Guidelines for Success.

A couple of things came about that made me want to know more.

  • I wanted to break away from being dependent on purchased onion transplants.
  • And I became interested in trying other varieties.

The more I read about hybrids (not only onions, but any vegetable) having less nutritional value, the more I wanted to find open pollinated varieties that would do well for me.

So I started buying onion seed and sorta went crazy. I’d get so excited when I was reading catalogs – on and offline – I’d forget to make sure that the variety met the criteria that I’d set.

  • Old Seed vs. New Seed

More than once I purchased onions from a supplier that was running a year end sale. I was sent onions for that year rather than those specifically packaged for planting the following year. (Example: Without realizing it I’d be buying 2014 seeds in December of 2014 to plant in 2015 rather than seed for 2015.)

Some vegetable seeds, if stored in a cool dry place, can remain viable for 3 to 10 years. Onions are not one of those.

You can get sporadic germination from second year onion seeds, but there’s no guarantee. To get the best results you need fresh onion seed each year.

In all my experimenting with onions this year, I’ve tried to start a lot of last year’s seed since there’s no point holding it over. Germination was practically nil in some varieties and very sparse in others.

  • Suitable Day Length

I’m fortunate that here in Virginia (latitude 37.95ºN) I’ve had success with all categories of onions: Long Day, Intermediate and Short Day.

I did however go a little crazy last year and order too many short day varieties when I needed more long day varieties.  Many of the long day onions are good storage onions and few, if any, of the short day onions last very long.

That’s usually not a problem for me.  For example, last year I ate all 400 of my short day onions before I had to worry about storage.  They were sweet and delicious!

Onions fall into 3 categories based on day length:

  • Long Day (North of 36ºN latitude) (Needs 14 to 16 hours of daylight to trigger bulbing)
  • Intermediate (most between latitudes 35º and 38º N) (Needs 12 to 14 hours of daylight to trigger bulbing), and
  • Short Day ( South of 36ºN latitude) (Needs 10 to 12 hours of daylight to trigger bulbing.)

The length of daylight in your part of the world determines which category you can plant and bring to maturity successfully. This is because hours of daylight (along with warmer temperatures) trigger bulbing.

If your area does not have the number of daylight hours needed to trigger the bulbing, the onions won’t bulb.

And on the other hand, if your area reaches the number of daylight hours needed to trigger bulbing and the onions have not grown enough leaves (the top green growth), they won’t get very big.

The further you are from the equator the more day light hours you’ll have in the summer. Your distance from the equator is called your latitude. (In the Northern Hemisphere the 36º latitude is indicated 36ºN.  In the Southern Hemisphere it’s indicated 36ºS.)

To find your latitude cut and paste this address into your browser: http://www.latlong.net/ and then type in your address and hit enter. Your latitude will show in the latitude box.

Number of Daylight Hours Trigger Bulbing

If a variety falls into the short day category, it’ll need from 10 to 12 hours to trigger bulbing.  Last year I was late getting my short day onions in the ground and bulbing was triggered before the plant had time to grow as many leaves as usual.  So overall, my short day onions were smaller last year because bulbing took place before they could grow more leaves.

Keep in mind that each variety, even within the same long/intermediate/short day category, has its own number of hours that will trigger bulbing.  For example, some short day onions take 10 hours. Others might take 11 or 11 1/2 or 12 hours.

Information on exact number of hours is hard to find.  I’ve seen some, but not much.

This might become very important if  I unknowingly order a long day onion that takes 16 hours of daylight to trigger bulbing because we never get that many hours of daylight.  Our max is 14 hours the first week in May.  (I do well with the long-day onion Copra.  Obviously it must only need 14 hours of daylight.)

You can get a chart telling you the daylight hours your area has on any given day by going to http://jan.moesen.nu/daylight-calculator/ and typing in your City and State. I saved the chart for my area to my desktop and that way I have it on hand.

Final Thoughts

This year, I’m taking my time and thinking it through so the seed I buy will meet the criteria I’ve set and give me the best chance for success.


Related Posts:

Garden Seed – Heirloom or Hybrid Information to Help Make the Choice

Growing Onions – Top 3 Guidelines for Success


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  • I am still not ready to think seriously about the 2016 garden and now I feel kind of guilty. I swear this year I am just driving up to your house to harvest onions!!!

  • Theresa,
    Thank you for clearing this up! Now it makes perfect sense why growing onions took more than a green thumb. I always thought my length of day was much longer than it actually is.
    On a related note, do you use the phases of the moon to give you the best planting dates for above and below ground crops?
    I wish you and your garden a fresh new year of growth and sustainability!

  • Made me smile Kate.
    But I know you’ll come through and get those onions ordered and
    then planted at the appropriate time.

    Suzanne, glad this post cleared up some things. Those charts take all the guess work out of length of daylight and latitude.

    I do try to use the phases of the moon when planting. BUT, if I run into a situation (which I often do) of having to either plant at the “wrong” time or miss the boat, I just go ahead and plant. I think planting by the moon gives us an edge as does the farmers almanac planting dates etc. Those practices have been used for centuries with success. They’re another tool in our arsenal to help us be even more successful.


  • Great information that lead me to revisit the table of daylight hours. I had forgotten our longest day is 15.36. I will have to find a place to get the onions growing earlier this year. I am getting so excited. I was so pleasantly surprised how well mine grew with virtually no input from me last summer. And that is thanks to you Theresa.

  • I agree with Toni. You got me started on an onion growing adventure that is not over yet, Theresa! This year I am starting several short day onions and hoping to get them going just as soon as I can. I’m sticking to some that have done beautifully for me last year, and trying a couple of new ones. Fun.
    I also loved growing shallots a couple of years back. I heard that they are actually perennials (can’t remember where) and I wondered if you could verify that?

  • Glad your onions did so well last summer Toni!

    Sandra, shallots are perennials like potato/multiplier onions. They’re planted in fall and harvested late spring. Some say that bunching onions are perennials, but I think that depends on where you live and if your chosen variety can withstand the cold. I’ve not grown shallots, but I have grown both potato onions and bunching onions.

    Can you tell me what varieties of onions you’re growing Sandra? Both the ones that have done well for you and the new varieties. Thanks.

  • Two years ago I left Cippollini Onions in ground (from Dixondale) and let seeds form. I wintersowed the seeds last winter and got Cippollini onions this year! All of these methods I learned from you!

    I have been growing and replanting shallots for 5 years now, and this year they were huge (2-3″ across). My neighbor and I are also trying to grow Green Mountain Multipliers from a local man who has resurrected the Potato Onion. Google Kelly Winterton Potato Onions. It’s a fascinating story!
    Merry Christmas Theresa and Readers!
    Julie Martin

  • Gladstone and Red Wing and Cabernet are ones that have done well for me Theresa. Copra – don’t germinate as well as I’d like, I don’t know why. Ailsa Craig have been disappointing. But as you know, I’m still an infant with regards to learning about onions, so much of my reports may be based on my errors. I am trying two kinds of shallots this year, and excited to see how they might act as perennials. I don’t love the multiplier onions that much, so perhaps these will be a tasty alternative.

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