Onion woes

[HellfireFarm]

Searched, there's discussions on onions but not quite my issue.

I got a pretty good germination (70-80%), but now that they've gotten 3-4" long they're starting to die out. I've lost at least 25% of what sprouted. They're on the same shelves as my starters. Warming mat was on to start, turned off for a while, wondering if that's the issue?

Pics coming tomorrow.

 

[JJJessee]

I use the warming mat to give the seed a little push, after they've mostly popped I move to a cooler shelf. but still lots of light.
I also give them a haircut when they start to get floppy.
They need a rich soil too.


Before haircut.

After;

 

[skullbiker]

I use the warming mat to give the seed a little push, after they've mostly popped I move to a cooler shelf. but still lots of light.
I also give them a haircut when they start to get floppy.
They need a rich soil too.


Before haircut.

After;

I also used to do what he ^ said when I grew onions from seed.

 

[Sulsa]

Keep them cold! They germinate fine between 50 and 60F and once they have sprouted temps around 40F is not an issue. I always sow them inside around 55F and once sprouted they go outside under plastic or in a cold unheated greenhouse. They will become way more sturdy and healthier this way!
The big bulk of my onions are grown from onion sets by the way, i plant them around March and harvest them end of June. I only sow special varieties, this year it's "cipolla rosso di Tropea" very sweet!!!
Plant out for seedlings is end of March and harvest end of August.

Edit: isn't your climate warm enough for sowing straight outside allready?

 

[HellfireFarm]

Keep them cold! They germinate fine between 50 and 60F and once they have sprouted temps around 40F is not an issue. I always sow them inside around 55F and once sprouted they go outside under plastic or in a cold unheated greenhouse. They will become way more sturdy and healthier this way!
The big bulk of my onions are grown from onion sets by the way, i plant them around March and harvest them end of June. I only sow special varieties, this year it's "cipolla rosso di Tropea" very sweet!!!
Plant out for seedlings is end of March and harvest end of August.

Edit: isn't your climate warm enough for sowing straight outside allready?

I started them beginning of January, trying for a decent size before transplanting. I just haven't done well with onions yet. Tried a few different approaches.

I see one answer suggesting keeping them warm, another saying keeping them cool...

This year I tried using cell flats. This is what I have now. I had a lot more a few weeks ago.

 

[skullbiker]

I used to do mine in my basement when I was up north, about 65°f. When they got to the size like yours in that tray I would pot them up to 7 oz. dixie cups. Cutting them back to 3 - 4 inches the first time was almost a must. As they grew out and could stand I would trim them longer.