Onions – Seed, Sets, and Transplants

Onions take two years to complete their life cycle. (This makes them a biennial.)

The first year, a seed germinates and grows into an onion. How big the onion gets the first year will be determined by

  • when it was planted,
  • how deep it was plant, and
  • how long it has to grow before daylight hours trigger bulbing.

Sets – What they Are and What to Expect

If the onion seed develops into a small bulb the size of a marble or dime it can be cured and planted again in the fall of the same year or the next spring.  These are the ones that are sold as sets in the feed stores and garden centers.

Lots of folks buy and plant onion sets and have good results.  Sets “can” produce  good sized onions that can finish (the tops will fall over) and be cured and stored. BUT – they don’t always.

You want to remember that when you plant sets — those sets are onions in their second and final year of growth.

The chances of getting full sized onions are especially good if you plant sets that are about the size of a marble or a dime.  If you plant sets larger than a dime they will most likely produce a good spring onion for you to pull and eat. If you leave that spring onion in the ground long enough the onion will most likely set seed and form the hard stalk that is part of that process.

Transplants from a Supplier

Overall — transplants (young onion seedlings) give you better onions than sets.

But — as with sets — size makes a difference. Usually – when you order from a supplier like Dixondale — you get a mixture of sizes but hopefully more of the right size.  The ones that are no larger than a pencil are the ones that will give you the best results.

I was unhappy with my Dixondale order this year for the first time in about 20 years.  They sent me either very tiny transplants or extra large transplants and not very many that were “just right”.

What usually happens with the tiny transplants:

If the transplants are really tiny they may not have time to grow to full size and may finish up in your garden as dime sized onions or a bit bigger.  These are the ones that you can use as sets for the fall or next spring.  (I had two varieties <amounting to two rows> of onions finish up as small onions this month because they were too small to begin with. Too big a percentage of small onions to suite me.)

Over the years I’ve had these small onions finish and cure in the hot summer soil (because I missed pulling them) and then grow again in the fall to produce spring onions for the fall and winter months.

onions that finished small

onions that finished small

The small onions (either the ones left in the ground or the ones I replant in the fall ) I use for fresh eating spring onions through February or early March.  I use most of them by March because I need the space for other things.  IF I left them in the ground longer –since this would be their second year — they would develop a hard stalk and set seed.  There is always the exception to the rule, but the vast majority of times — that is what you may expect.

As mentioned above, if I planted these dime sized onion sets in the spring I’d have a good chance of them producing  full sized onions. (I don’t use them in the spring however, because I want to use the space for onion transplants.)

What usually happens with extra large transplants:

If transplants are too big you have a bigger chance of the plant making a hard stalk and setting seed.  Then you have to use the onion right away for fresh eating — as it will not cure and cannot be stored. My Copra (long keepers) onions that Dixondale sent me this year were way too big and more of a percentage than usual have developed hard stalks in the process of trying to set seed.

Growing Onions from Seed and Using your own Transplants

I’m convinced the absolute best way to get great onions is to start your own from seed and then transplant those seedlings to your garden in plenty of time to allow them to grow a lot of leaves and roots before daylight hours trigger bulbing.

Even though the transplants from growing your own seed may be very tiny — they will grow better than any transplant from suppliers. Yours will not be out of the ground as long as the ones you receive from someone else and in all probability will not take as long to recover after transplanting to your garden.

This year I started my onion seed in plenty of time — but then I was late getting my own transplants in the ground because I couldn’t find room for them. I kept waiting to take something out and by the time I got the onion seedling planted it was too late and I knew it.  Nonetheless, I know what I did wrong and believe me — I’m planning ahead and having the beds ready for MY onion transplants in February and March of 2014. I usually order at least 1500 transplants from Dixondale, but in 2014 I want most of the 1500 to be my onions from seed rather than Dixondale.

Final Thoughts

I hope this post will answer Sandra’s questions that she left as a comment on a previous post and answer any questions you may have had regarding onions.

Onions are a great crop to grow in your effort to become free from dependency on big agri-business.  They are an easy crop and the more you know about them, the more successful you’ll be.

I want you to be successful, so if you still have questions I hope you will let me know.


Other Onion Posts:

Other Onion Posts:

Onions – Tip – What to do with the Small Ones

Onions Plants – A Bonus Can be Green onions in Winter

Onions – Why Grow A Lot?

Onions – Starting from Seed is Easy and Economical

Onion Sets – What You Need to Know to Get Better Results

Growing Onions

Bunching Onions – A Perennial Scallion Patch

Onions – More Reasons to Plant

How to Have Garden Onions April thru January


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  • When is a good time to start your seed for outdoor planting in spring or for all?
    Do you start them indoors?

  • Betty, I talked about this in the post Onions – Starting from Seed is Easy and Economical So you may want to read that for more details.

    Rule of thumb is to start your onion seed 8 weeks before you plan to transplant. This year I will start mine in a bit earlier in January than I did last year. I’ll let them germinate inside. I’ll tape up the jug and put them outside to grow after that. If you are set up with lights to grow inside — you can let yours grow for about 6 to 8 weeks inside and then harden off and transplant. Since I am not set up to grow indoors I have to put them outside right away to insure that they will get enough light.

    Betty, I visited your new website and was delighted to discover you were a bee keeper as are quite a few of my readers. In light of the serious situation with bees — I hope your articles will do even more to attract attention for the plight of the bees that can quickly turn to the plight of mankind.

    I’ve included the link to the articles and hope TMG readers will take this opportunity to read some of them.

  • Hi Theresa

    They’re a great company and stuff happens, but like you, I wasn’t very happy with my transplants from DixondaleFarms either. The sweet Spanish and Walla Walla look great, but the other three varieties are exactly as you described with lots of huge and tiny plants. Since the Copras are my mainstay onion for storage, I’m a bit worried now I’ve read this.

    Should this happen here, would snipping the center stalk /seed head early on, help at all? (just thinking out loud)

    Last years transplants were really good, producing almost totally uniform bulbs averaging about 3+”, with only a small amount of smaller ones. Nothing tried to go to seed either.

    I did plant a row of white sweet Spanish from seed. It was a very late decision and my timing was off by about a month. Seemed like it took them forever to really start taking off (I was actually going to rip them up until a voice of reason talked me out of it 🙂 – Thank You!) but in the past month of growing, most of them have caught up to the transplants in size! I’m just chalking it up as another lesson learned this year.

    Knowing how critical timing is for a good crop, I’ll be ready 6 months from now! I’m planning to grow all 5 varieties from seed since it was so easy. Already scanning the web, looking for a good seed source.

  • Good having your input Jack and especially thrilled to hear that your sweet Spanish from seed have caught up with the transplants! That is just great news!!

    I have quite a few readers tell me that they were unhappy with their Dixondale transplants. Hate to hear it — but I definitely am not going to depend on anyone other than myself from now on to make sure I have onions for the year.

    There are many who will be encouraged by your testimonial as to how easy it is to start and grow from seed!

    I too depend on the Copras for my storage onion — so I’ll be anxious to see what happens.

    Oh — almost forgot — when you cut the hard stalk — it won’t save the onion as far as curing and storage. Just use those a fresh onions because they just won’t cure or store.

    Again — thanks for taking the time for this great input.
    Keep me posted and let me know what happens when all is said and done.

  • Thanks for the help and advice here, Theresa, yes you answered my questions. Many of my onion transplants went to seed this year, and overall my onions are smaller than last year. I also grew some shallots – they went in late and there is nothing developed underground, neither have they fallen over, so I’ll give them a bit more time. I planted two other heirloom onions from seed (can’t remember the names of either right now, but one was a red onion Italian.) The reds are small, but uniformly so – about 2 inches at most. The whites are very small indeed. The yellow finches are loving the onion seeds in my garden – but I’ll still try to save some seed from these heirlooms and see how it goes next year. You are right, depending on one source for a harvest of any type is putting all your eggs (or onions) in one basket!

  • In your email to me Sandra you said “Jack’s comment is a lot like what I had from the Dixondale transplants too.” Sounds like that is why you had so many go to seed.

    Dixondale really messed up I think, but I’m going to use it to encourage myself to be dependent on me rather than them for my onions. As you said — depending on one source for a harvest of any type is putting all our eggs (or onions) in one basket.


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