How I do onions from seed


Thanks for the info, well this winter was mild, but the last few were atypically brutal.
Could someone please go over step by step on to get seed from these biannuals?
I usually plant in the spring, and they are not ripe to fairly late in summer. Do i pull them out and put them back in? Is that what you guys do? i read I think that if you have a harsh winter to plant in the spring.I would not mind growing by my own seed. I can still buy others too.

So you do plant in the spring a 2nd time for seed? The leftovers, were not the best, so small and such i didn’t even see them (I plant them all over the yard, room is an issue, so wherever I have an open spot)


My climate is likely a bit atypical, but here’s what I do that seems to work (my growing season is too short to mature many crops outside):

Seed gets started indoors ~Feb 1. Gets xplanted to the greenhouse after most have a couple of leaves and grows in the GH until roughly pencil diameter. Then gets xplanted again to the garden roughly end of April. At this point they are roughly the size of purchased onnion plants, and I clip off some of the tops to balance the root loss. Anyway this is my pattern for growing onions here.

For seed production, I try to save a few of the larger onions that are in storage from the previous fall that have desired traits (large, no disease, etc). We use up any that have started to sprout or go bad, so in effect we are selecting those out of the gene pool. Around March 1st I select a few of the best onions for planting for seed. Again in the GH (cause our season is not long enough to mature onion seed reliably). After a few weeks those onions start to grow, they generally will flower in August (give or take some). I let the seeds mature to almost the full dry stage on the plant. But try to cut and complete the drying inside, since fully dry onion flowers tend to shatter and scatter the seed. When dry I rub the flowers/seed between my hands to break apart the seeds from the dried parts, then winnow.


From my notes…
Allium flowers are self-infertile. The flowers open over a course of 30 days. Onions are insect-pollinated out-crossers. They may cross with Japanese bunching onions but do not cross with chives or leeks. Do not save seed from onions that produce seed in the first year. Rather plant selected onion bulbs (grown in the prior year) in the spring for seed.
It is not uncommon for onions to produce many infertile seeds. To separate these out, place all the seeds in a bucket of cold water. Fertile seeds sink to the bottom and infertile seeds float to the top and can be carefully poured off with the water. Dry seeds immediately.


Good info. I can plant for onion seed soon. I do have a few, they are not sprouting either. So good examples. Actually all i have left is a few shallots, but it should work the same. Thanks all for the info.


Onions may not mind a touch of snow - they’re tough


That’s a good idea to plant the best stored bulbs for seed in the early spring, too. Mostly I need to plant in the fall to get a head-start for growing for the seed to mature but I’m going to try some in the spring, if the snow goes early enough. The hard thing for me is to plant those very best bulbs instead of eating them! I like to plant 9 to get enough for reasonable genetic diversity. But the nice thing is they don’t take much space and really are pretty.


For those interested in seed saving I’d highly recommend Suzanne Ashworth’s book “Seed to Seed”. It’s a great resource. It wasn’t written yet when I first started saving seed but I sure appreciated it later.
And for a little more about growing onions, if I might mention (though I’m really not trying to toot my own horn) I have a fairly long article on growing onions on our website. For many years I wrote for “Countryside Magazine” and later put most of those articles (updated in some cases) on our website, just to share. It’s at:


Good stuff Sue, thanks. It does matter where you are. As you can see I can produce large onions from seed in the spring. I started mine Feb 17, they are only 2-3 inches tall now. Today it’s 42F, and sunny, they are going outside.
Yeah my 4 foot, 4 bulb T5 lights are hot and the onions don’t like it. I moved them to a 2 foot 2 bulb T5 set up. less light but not hot, Outside I will leave them in the sun 30 minutes, and move to the shade, first time outside. This helps start the acclimation.

The figs I started from cuttings love the hot strong light! As do the pomegranates also rooted from cuttings.

Parfianka pom


I realize this is an old thread and it appears I am getting a very late start at sowing onion seeds but I’ll give it a shot anyway. When I ordered my tomato seeds I ordered a pack of onion seeds just for the heck of it. I got an heirloom variety called crimson forest. My plan is to throw them in some seed starter in a large container and grow them under grow lights or in natural sunlight if the weather permits until transplant time. I suspect my maters will go in the ground around mid may. If the onions are still quite small after 4 weeks would it be okay to plant them out when I do the tomatoes?


I planted my onions last weekend. Later than usual butt they got to big last year so i waited a bit.

Post pics and keep us updated! I’m growing copra ailsa craig and redwing.


I’ve planted small seedlings and they grow fine - they’re just smaller bulbs when mature. If still small when transplanting you might give them a little extra care by covering them for a few days when planting (helps no matter the size). I wonder if you’re weather is such you might plant them direct? I don’t know that variety but it does depend on how long a season it needs whether you’ll get large or small, but either way you’ll still get edible! Sue


Onion update, almost ready too transplant…


Looking good Derek. I am xplanting mine outside this week…


I found this online in a ‘onions from seed’ guide…

  1. Harden off, but protect from chilling
    Eventually the onion seedlings stay outdoors 24/7, provided temperatures are well above 46°F (8° C) at night. Consistent exposure to temperatures below 50°F (10°C) for more than 10 days can cause onions to bolt rather than producing big bulbs.

makes me think I should maybe wait another week or two. Still pretty cold here at night.


Interesting, I had not heard that before about the need for >50F for onions. If I did that here, they would never go outside since we have cool nights and even in August it can be <50F at night.

I generally try for a time when it is mid 40F’s or better most nights and then they go out. I have not seen any problems with bolting, but have not paid close attention to the night temps either. When I lived back east, it was common for people to seed onions directly (and to xplant them) when it was still quite cool at night, including some frosts. But it has been several decades and I don’t recall the finer details of growing onions there.

I suspect that the variety of onion will make some diff here, and could well be that long vs short day varieties also would react differently. Perhaps someone who knows the details can enlighten us.


Ditto what Steve said for me, too. I do wait till it feels like the frosts are over (usually early June here) to plant so i don’t have to cover them, but i’ve transplanted early, too, They just wait till it warms up a bit to grow. I’m setting the flats outside on nice days now. I keep them trimmed to 4-5" which makes it easier to handle them when transplanting, and i think they’re sturdier.

I do sometimes get a few bolting and just nip the flower bud off, but it’s not widespread nor every year. It could be due to cold nights though. Likely depends on variety and location, like so many things. Interesting comment though. Sue


I transplanted mine out April 22. Temps dropped down to 22 degrees that night which was a bummer. They have all seemed to have surprised, but are just creeping along. Hopefully the warm temps this past week will kick start the growth.


Planted 4 rows of onions in my garden yesterday. This is the size I put them out this year. Last year I let them get too large before transplanting… I trimmed the tops back and also sprayed them with wilt-pruf stuff, hopefully helps them adjust better.


I was too late to start from seed so I bought some starts that size. I planted two 27 gallon planters full. I wish I had more garden space.


Nice, I ended up renting a community garden plot this year also that I havent even started planting. Might have gone a bit overboard! Shouldnt run out of onions next winter for sure…


My attempts to start onions from seed this year were a total failure. I’m not sure what went wrong. I had killer success with tomatoes but onions flopped. I ended up buying some starts as well.