They look fine to me. It is normal for the seed leaf to look like that. Eventually the seed leaf will completely brown and wither just like the seed leaves on other plants.

But yes, it is better to sow them in deeper pots so the roots have plenty of room. I use 2 lb. yogurt containers that are about 4.5" deep.

Concur.

Thank you. I didn’t even think of it as having a seed leaf. Make sense. Do you all think it’s wise to plant them up into deeper containers or just leave them in the flat. They probably have another 6 weeks inside under the lights.

Can some give examples of what they do to start onion seeds inside successfully? My attempts to grow onion seeds usually ends up with them sprouting like that and then they grow very weak. Is warmth inside a problem? A fan blowing help? Soilless starting medium bad?

I sprout them at 75-80F (September, in a converted garage in the summer) in compost-amended soil. Keep moist. 8-10 weeks and they're ready to plant out. Yours grow weak? What does that mean? They may fall over when they are six inches tall. Need to keep them trimmed to make them stay reasonably vertical.

Yes, keeping them trimmed to around 4" should help them stay upright. The more true leaves they get and the thicker base stem they get the more they stay upright.

uncgdc - I've never tried to transplant onions until they are around 10 weeks old so I'm not sure. I know a lot of people grow them in flats so it's probably not a problem. I probably wouldn't risk transplanting at such a young age myself. The roots my be pretty tangled come time to plant out but once they are bigger they are pretty tough and can take some rough handling.

Thanks LoneJack. Sounds like a good plan.