How to Grow Onions – especially bigger ones –

If you want to get bigger onions  allow more room between onions.  Six inches between each should do the trick.

Although this is an important key to getting bigger onions — keep in mind it’s not the only key.

  • Different varieties grow to different sizes.

For example: In general, Copra – a great keeper – is not going to get any bigger than 3 to 4 inches across. Whereas Ailsa Craig – another long day variety — has the potential to get up to 8 inches across and weigh in at 6 pounds.

For great growth – onions also need:

  • To be planted early enough to grow strong roots and more leaves before bulbing is triggered
  • Soil high in organic matter
  • Soil that drains well
  • Mulch to keep the moisture in and the weeds down. (Onions don’t compete well with weeds.)
  • Planting dept of only 1 inch

Planting Sets?

Overall — transplants (an onion seedling grown from seed this year) grow the best onions.

If you’re planting sets (little onion bulbs) — rather than transplants choose the small sets — about dime size.  The smaller sets make the biggest onions.

(You might want to review my post Onion Sets What you Need to Know to Get Better Results)

What I do

I don’t have a lot of use for great big onions, so I usually plant mine about 3 to 4 inches apart.  (I don’t use a ruler — I just go by eye.) And I get nice size onions and in spite of the fact I don’t set out to get great big ones — I do get a few.

Day length is critical

Day length is what triggers bulbing. Some onions take more day length than others to prompt this process. (If onions don’t bulb they can’t get big.)

To find out what day length onion you need visit this page of the Dixondale website.

Also — if you explore their site — remember they’re not organic.  Also — as an organic home gardener — they give some advice I would not follow.

If you end up ordering from them — keep in mind some of their onions are from Monsanto owned companies.  Just email and ask them.  They’re very cooperative about telling you.

Just so You’ll Know

If you buy transplants from your local feed and seed store — they’ll be selling onions that are the correct day length for your area.

If you buy seeds — the seed companies don’t always tell you what the day length is. Do a little research online before you buy.  If you live in the deep south and order onions for long days of the far north — those onions will not bulb for you because they won’t have enough day light hours to trigger bulbing in long day onions.

If you live about in the middle of the country like I do (Virginia) — almost all day lengths will do ok for you.  I grow short day, intermediate, and long day onions.  All do well.

Final Thoughts

If you’ve come across this information a bit too late and have already made some “imperfect” moves — just chalk it up to learning and move forward. The worse you can do is get some great spring onions or some small sized onions.  Not such a bad consequence.

May all your onions be just the right size! 😉


Other Posts on Onions:

Growing Onions – Determining When you Should Plant

Onions – Those to Enjoy as First Fruits and Those to Store

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

Onion Trivia

Onions – More Reasons To Eat them Fresh

Growing Onions – Problem with Rot

Planting Onions – How to Keep Your Transplants Fresh Until you Plant


Organic gardening is easy, effective, efficient —- and it’s a lot healthier.


All content including photos is copyright by TendingMyGarden.com.  All Rights Reserved.




  • Theresa, It’s such a thrill when you harvest decent sized onions for the first time like we did last year. I studied up on all your articles and followed the advice given. Hey presto – large onions!!!
    This year I’m worried because I have my onions in, but the ground has had a couple of freezes since. I’ve mulched them, but I’m hoping they’ll be ok. It’s hard to tell because the tops have not put on new growth yet – just planted them last week.

  • I don’t think you need to worry Sandra. Onions can take the cold pretty well. A few freezes won’t hurt them — especially if you have them mulched. It’s been a bit cold for them to put out new top growth, but with the warm week or 10 days ahead — they’ll start.

    It seems we gardeners fret over all our crops but they’re a lot tougher than we give them credit for.

    I still fret and I’ve been growing onions 35 years! I just put in 750 and the way I fret over them you’d think I’d never planted any before. My excuse for fretting this year was that I thought there was a lot undecayed organic material in the soil (leaves) and I was afraid there was not good soil to root contact. In spite of my fretting — they’ll probably do just fine. 🙂

  • Hi Theresa

    For some reason my onion seedlings don’t look very good this year so far, so I’m thinking of ordering some plants. I know that you’ve mentioned Dixondale, and it looks like they have good prices, selection, etc.–but they’re in Texas and I’m in northern Michigan. Do you think that the long trip will be hard on them?

  • Hi Tom,
    My onion seedlings (except for the Copra variety) are not looking good this year. I’m going to try more — just to see if maybe it was the weather.

    Dixondale knows how to ship onions and the onions will make the trip just fine. The minute they arrive at your door, remove them from the box; take the rubber bands off the bunches; spread them out so the air can get to them. (Keep them out of direct sunlight. I usually put mine in garage or on my enclosed porch.)

    I usually use some low cut boxes to put them in until I can plant. It’s very important that you not leave them packaged or bundled. As long as you spread them out a bit so the air can get to them, they’ll be fine until you can plant.

    I usually plant mine within 3 days of arrival, but I’ve had times that a bundle or two didn’t get planted for a month after arrival. They still did ok.

    You might want to send them a note with or before your order inquiring about Monsanto owned varieties. They are very cooperative about telling you what comes from Monsanto and what doesn’t. I won’t buy any variety that is a Monsanto owned variety.

    This year I found out one variety was Monsanto owned after I ordered. I wrote to them and they recommended a similar variety and changed the order for me.

    Let me know how you do.

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