Garden and Orchard

Planting Onions From Seed


See also How to Start Seedlings Indoors

Growing Onions from Seeds or Sets?

I’ve grown most of my storage onions from seeds rather than ‘sets’ for years now. Originally I started sowing onion seed because I wanted to try some new varieties. When you purchase sets your choices are limited. There are yellow, red, and maybe white storage onions available in net bags widely available at hardware stores, nurseries, and the big box stores every spring.


Way back in the day (I’m dating myself a little bit!) I could get those bags of onion sets for about 2/$1. This year (2013) they cost $1.69 a bag. Not a bad deal if you are short on time, but pricier than starting from seed. You also get quite a few that are shriveled or moldy, so the 100 sets you start with is reduced a bit. The most recent packet of heirloom onion seed I bought came from Seed Saver’s Exchange in Iowa and ran me about $2.49. I just planted the last of those seeds after 3 years. They are ‘Yellow of Parma,’ an Italian variety that touts excellent storage qualities…to which I can attest. We still have a handful of sound specimens in my ‘root cellar’ and they definitely outlived the onions grown from sets.

Onions in my garden last year…right next to the strawberry bed.

Besides the fact that it is less expensive to grow your onions from seed and you have a greater choice in varieties, I have one more reason for choosing to plant onions from seed. I’ve found that onions from seed tend to ‘bulb up’ better than the onion sets purchased in the little net bags. Many of the sets produced very small bulbs or else they never formed a bulb at all. Instead, the bottom of the onion grew to about the same width as its ‘neck.’ Those puppies don’t store well and should be used up soon after harvest. The other problem I’ve found with onion sets is the tendency to go to seed in their first year.

A casualty…onion sets often have quite a few moldy or shriveled specimens in each bag.

Onions Are Biennials

If you are interested in saving seed from your onions to grow future crops, you will need to leave them in the ground over the winter to produce seed the second year. A good layer of mulch will protect them from freezing and rotting. The reason onions grown from sets sometimes flower and set seed their first year is due to the process used to raise them for market. Onion seeds are planted out, allowed to grow to the size of a small bulb, then they’re harvested, dried, and shipped to garden centers. We plant them out in our garden and give them the water they need to continue their life cycle. Sometimes this treatment tricks the onions into ‘thinking’ that they have lived out their first year, went dormant, and now they should produce seed for the next generation. I’ve never had onions from seed go to flower their first year, so I tend to get a better yield from them than I do from the sets.

Onion sets, ready to plant.

Planting My Onions This Year

Now don’t get me wrong…I still plant onion sets sometimes. I mean, really, how do you walk through the garden aisle at the hardware store without having a bag (or three) of those cute little onion sets jump into your cart? It’s nearly impossible for me to resist the temptation, even though I grow more onions than we usually can eat. So I already spied the onion and potato sets last weekend, but my willpower remained intact. However, it does tend to crumble after one or two trips to the hardware store. And now that I’m writing about the pros of planting onions from seed, I feel it’s my responsibility to plant both sets and seeds this spring to show you the differences this fall. (Sorry folks, that didn’t happen!)

The heat mat will help my seeds sprout quickly.

For Complete Seed Starting Instructions…

Please visit the chapter I wrote for Farm to Table Through the Year. My chapter is May and I give step by step instructions for starting seedlings inside and hardening them off.

But, I digress. Yesterday I planted seeds for the following: ‘Lancelot’ leeks, bunching onions, ‘Yellow of Parma’ storage onions, and ‘Copra’ storage onions. They have been watered in, labeled, and tucked into recycled ‘mini-greenhouses’ on a seed starting mat in the basement. Now I must wait for them to sprout and grow a bit before I transplant them into larger pots and move them to the greenhouse. I’ll harden them off and plant them out in rows when our temps remain above freezing for a bit.

Onions are biennials, meaning they flower and produce seed in their second year.

Do you plant onions from sets or seed? Which do you like better?

33 Comments on “Planting Onions From Seed

  1. I enjoy growing onions from seed. I first started growing green onions from seed but longed to grow bulb onions so ordered seed from Wilhite Seed Co. in Texas. The first year I planted them in the garden and they came up but froze out the first freeze. Then I tried planting them in my home made cold frame. The first year was a success and I made over 400 very nice size bulbs. Last year they started out very well but a cold hard freeze in Feb. killed most of my plants so I only had a hand full and they didn’t bulb up very large. I’m hoping this year will be better and have mulched the little onion plants with pine straw.

    1. I haven’t tried growing them in a cold frame…great idea! Were you trying different varieties of seed, or the same kind each time? I know that different varieties need different amounts of light to mature into bulbs. Thanks for sharing your experience!

  2. I over-crowded my garden last year, and the onions didn’t get enough sun and space. They were tiny. ๐Ÿ™ Trying again this year.

    I did have success with garlic, though! I split a head of garlic into cloves and planted each clove in the fall. By late-July I harvested full heads of garlic! I bet this could be done in pots, too.

    1. Hi Sibilant,
      I’m bad about trying to stuff too much into my garden too ๐Ÿ™‚ I’m getting better however, and I will actually thin seedlings out now.

      I love growing my own garlic! And yes, you can plant it in pots too! Best wishes with your garden this year!

  3. I have onions from sets growing now, white and red onions. I do have some seeds too, but we haven’t planted any yet. I’m hoping to this weekend. I purchased some leeks too, but I thought we shouldn’t plant those until the fall? Can I go ahead and plant them now for Spring? Thanks!

    1. Hi Mary,
      If you are in the same climate as I am (northern US) you should start leek seeds under lights early, about 8 to 6 weeks before last frost. Then plant out when your days warm up. If you plant them in the fall, it could work if the seeds are planted late and then they will germinate in the spring when the soil warms up. They should be a couple of inches across at the soil line when harvesting. You can mulch and keep in the garden for a month or two, but won’t grow over the winter.

      Have fun with your garden!

  4. Hi Carey!
    The Ailsa Craig sounds great ๐Ÿ™‚ I like getting my seeds online too. But every time I go to the hardware store, some more packets make their way into my cart. Not sure how they do that. ๐Ÿ˜‰
    Best wishes with your onions this year!

  5. I planted Ailsa Craig from seed last year. It was a drought year and other than a few tiny bulbs they nearly all came out big, firm and crisp. It was the first time i’ve planted onions so I didn’t plant enough to get to the storage stage. This year I have many more under the grow lights…I’m hoping for good results again. The reason I began seeds instead of bulbs was not only because of cost but because I order my seeds from reputable companies on line and adding onions to my growing list of seeds was as easy as a click of the computer! Didn’t have to leave home!

  6. Very interesting. I was just wondering if I should move more towards planting onion from seed. Started my first attempt this spring. I hate how the bulbs go to seed, so I’ll be so pleased if planting from seed takes care of that. I can’t wait to see what you have to show of your bulbs verses seed this fall.

  7. I haven’t been very successful with onions. I tried both ways. I think I just need a dedicated bed for them. My soil is so bad neither had a fighting chance. =0(

    1. Hi Holly!
      Is your soil heavy clay? Onions seem to like a light loamy soil best. You can improve sandy or clay soils with the addition of compost. I hope you have better luck next time!

  8. I’ve been failing at starting leeks and onions from seed every year. and I LOVE leeks & onions. I can’t seem to manage to grow them past the thin spindly stage into the pencil size they are suppose to be when transplanted. I grew onions from sets last year with decent success, but would love to know some tricks and tips on how to get them to grow to save money and I heard they can be bigger. My leeks are doing terrible again this year although Im having much better success with the red onions.

    1. Hi Homestead Mama,
      I’m sorry to hear about your leeks and onions. I know they don’t like heavy, wet soil. Sandy or well drained is better. Also, I never wait that long to transplant my leeks. I just haul them out to the garden when it’s warm enough, dig a trench, dump out the pot of leeks and tease their roots apart, then lay them in the trench. I’ve found that I can plant them pretty deep in a trench with the top couple inches sticking out of the soil. Press the soil around them lightly and tamp in on either side of the row. Keep them moist, but not soggy. You can lightly dress with fertilizer for rooting (last number a bit higher on the n-p-k ratios). Later on they like a mild organic fertilizer like kelp or fish emulsion.

      Best wishes!

      1. I grew leeks from seed last year in my greenhouse for the first time and I put them in the garden when about pencil lead size, so tiny it was like planting a heavy piece of thread. Didn’t have a lot, but mulched very heavily with straw for over winter and I think it was about Dec. when I brought the last ones in. I like them well too. This year i will do onions from sets and froim seed, the tiny plants are coming up now in my greenhouse. I don’t use a heat mat as I don’t have money to buy one but they’re doing pretty good in the greenhouse where the temp. varies from 40-85*. Did green onions from seed in the garden last year and they did great and harvested the last into Nov. Had never did that before. Great posting. Thanks.

      2. any tips for getting them to grow to pencil size? I start my seeds inside, they have been going for 6 weeks now and still super super thin! do you boost the seedlings at all to get them to the pencil size?

  9. I’m trying Leeks from seed this year- I’ve never done onions before, but would like to try them, since we eat a LOT of onions! I’ll probably do sets this year, and maybe try seeds next year. The leeks have sprouted and are growing in my windowsill til its warm enough to plant them . ๐Ÿ™‚

    1. We are growing lots of leeks this year. Leeks are very popular in Poland which is where I first tried them. I even made a simple leek soup that went over quite well with our guests as well as the family. They have a more mild flavor.

      1. Hi Becca and Rachel!
        I like leeks too! They seem to have a milder flavor to me than green onions. Tom informed me last year that he wouldn’t mind if I planted them in place of the green onions from now on. I’m not completely sure that I want to give up my little green onions….but I do enjoy having the leeks in the garden too! Plus, they keep well into the winter. If you mulch them heavily with straw, you can keep digging them until the ground freezes solid.

        Have fun with your leeks, Ladies! (That sounded funny, didn’t it?)

  10. I’ve always planted from sets and have not been happy with the size. Last year we bought seeds, the same ones from SSE that you have. I didn’t really do a good job with them though, we were in the middle of our move and they just sort of fell by the wayside. I really need to try again.

    1. Hi Jenny,
      I’m sure you’ll be totally shocked at this news, but I’ve done the same thing. ๐Ÿ˜‰ The first couple years that I started my onions from seed, I either let them dry out too much, or waited too long to plant. You also need to take a little more time to transplant them because they are so small and delicate. I’ll try to do a post when I plant them out and give some instructions and share pics. I hope your little onions do better next time!

      Oh, and you’ll like that variety of onion. I can’t say that the flavor is much different than the others I’ve tried, but they have kept really well for me.

    1. Hi Kristi!
      It’s nice to have some small onions ๐Ÿ™‚ Especially when you just want enough for an omelet for 2 or something like that. I have having a half a cut onion in the fridge…no matter how tightly contained, it ends up stinking up the whole fridge! But I don’t like peeling umpteen little bitty onions to make a big pot of something either. I must be really picky, but I like having a range of sizes!

      Let me know how it works out!

  11. I always do sets, though the last few years I had the seeds on hand just never got around to it. You’ve inspired me! I’ll definitely try them this year! thanks.


    1. Howdy Lisa!
      I did that for a while too ๐Ÿ˜‰ It’s tough getting all those little plants started under lights each spring. I try to be a little picky about what I take extra time to raise from seed…but I found the onions to be worth the extra effort.
      Best wishes!

  12. I always used to grow onion sets but this year picked up seeds because of always finding so many moldy/rotted ones in the bag of bulbs to plant out. Last spring I helped my organic farmer friend plant out her onions she had started from seed and they were so healthy and grew so big and tasty that it inspired me to grow them from seed this year.

    1. That’s awesome Annie! I’m always amazed at how those little bitty slips of green turn into great big onions ๐Ÿ™‚ I’m easily amused! Best wishes with your onions!

  13. I planted from seed for one type, the others say to sow into the ground. So, in about two weeks, the garden should be ready for it and I will give it a go.

      1. Sweet Spanish Onions are what I started already. I also started my leeks. Then when the garden gets started I plan to put in some Sedona onions and Red Wing onions. I’ll also be planting chives.

      2. Mmmmm, sweet onions sound yummy! Sounds like a great selection. ๐Ÿ™‚ When my son was a little guy (we’re talking a ‘few’ years ago here) he loved to pick chives and walk around the yard eating them like a farmer chewing on a stalk of hay. I love having a bunch of chives in the herb garden!

    1. Hmmmm, it’s interesting that we had opposite experiences last year! Thanks for sharing your experience Becky! Best wishes with your onion seed saving!

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