How I do onions from seed

Planted in bussing tote, pro-mix with a little osmocote +…
Just a few pics. Probably started a little to early this year, 3-13, some were starting to bulb a bit when I transplanted them to the garden this past weekend.

Ill try to post occasional updates this summer as they grow and a final harvest pic also…


Very nice.

I like your walkways!

Hey Derek,
Where in zone 3? And what varieties do you grow? I assume you do long day onions?

Thank you.

These are Copra and Redwing from Johnneys Selected Seeds. Im in ND. Someone asked what the siding is for on another forum, its multipurpose, it reflects light for the plants, decreases soil temp, helps conserve moisture and acts as a weed barrier. Also it protects the drip lines from UV/sun and gives me an easy way to know how far apart to space the rows.


Derek, I don’t know that you started them too soon. My schedule in zone 5A is to plant onion seed Feb 1, they get xplanted to the greenhouse when they are 1/16" size. Then outdoors around now when they are 1/4 - 3/8" size.

This is the schedule I have worked out for here that seems to work well. It also has the advantage of giving the onions a few extra growing weeks which they can’t usually get outside here.

So I would think you’re onions will do fine, but I don’t really know your climate that well.

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When I start onions, I usually do it in January!

Im using new lights this year and the grew much faster than they used to. The largest had probably 5/8 inch bulbs when I planted them out and the tops were over 1ft long. Typically I plant them out before they even start to swell significantly. Hoping they get large and dont end up going to seed toward end of summer. Next year Ill start them a couple weeks later Im thinking…

Hmmm, maybe your new lights are too good, or you were leaving them on too long. I’m not familiar with those varieties, but if they were long day types, and the lighting period was long enough that could have switched them to bulb mode even if they were still small.

I’ve had success trimming back the tops at the point of the final xplant to outside. Helps balance the leaf load to the reduced roots, but also might cause the plant to “rethink” bulbing for a while, IDK. I generally grow out my onion starts in natural light, which is pretty limited in Feb-Apr, so bulbing isn’t an issue for me.

Let us know how these do.


might have been on too long… I dont remember what I had them set at but probably 18h/day, had a bunch of other plants going and watned to maximize growth, didnt think about photoperiod effect on onions, I guess if I end up with hundreds of 1 inch diameter plants going to seed, will be lesson learned.

I’m trying potato onions and shallots this year. You plant them in the fall like garlic, and they divide into a cluster. No seeds necessary.

Thanks for posting that. Unlike fruit growing, I actually think I’m a pretty good gardener and usually do quite well, but one exception is with onions. Every darn year I plant a row of those little onion sets you buy by the pound at various places and plant them. They always come up and take off really well, but when they get to be a little smaller than a golf ball they just stop growing and stay that size a while and then start to die. Any idea what I’m doing wrong? Perhaps I should try seeds and your technique. Also, I leave them barely covered in dirt. Someone suggested I probably need to remove almost all the soil and only leave the roots under the bulb in the dirt. Is that true? Thanks!

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Don’t plant those onion sets


I have the same problem. Never been able to grow onions larger than cherries. I also grow them from sets.

Why not?

here is a pic of the ones i just planted, some i didn’t have room for in the rows. If you want big onions u need to plant small growing plants, either purchased or started yourself. Sets will never do really well from my experience. Also they need to be watered consistently, they don’t like to dry out much. Here is a picof my onions from a few years ago. another pic from a different year.


Because onions are biennial. First year, they grow bulbs, second year they send up a seed stalk. Onion sets are first-year plants, so when you plant them the second year they’re already past the optimum bulbing time


Now THOSE are some onions! WOW!!! I’m so jealous!

@ltilton That is great information and I had no idea. Does that mean it takes 2 years to get large onions like @TheDerek 's? I’m pretty sure others plant and harvest big onions the same year…though they may well be from plants and not sets.

If you don’t like sets, what about those small plants that come in bundles? They always look 1/2 dead by the time they make it to the stores here, but I could try some if you think they are more likely to make big onions?

I’d agree with ltilton, seriously. There are quire a few onion varieties, some are sensitive to day length (need either a longer northern summer day or shorter southern day) to trigger bulbing. And there are day neutral varieties which make bulbs regardless of day length. When you get sets, you rarely are told which type you are getting. If those sets you’ve been getting were of a variety that needs northern latitudes to bulb you would get the results you’ve said. It would be nice to think that the local shops would carry stuff that grows well locally, but as we know with fruit trees, that isn’t always the case.

You could switch to buying seed of a variety which is matched to your latitude (better seed co’s tell you where a variety will work) and start your own onion plants from seed next winter-spring. Or some places sell plants of named varieties too, although I agree the shipping can be hard on the plants. you might still be able to order some onion plants for this year.

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