I'm in Nebraska, zone 4/5. I couldn't put any onions out yet because of the chance of freezing. If the green stems froze it would set them back and that would hurt the crop.
You said something about hardening them off. As long as they won't freeze it's probably fine. Even hardened plants can freeze, though.
What beautiful plants. Great job with them! What do you make with them? Do you make a lot of salsa or these are just onions for the entire fall/winter/spring?
Heidi in Nebraska

Thanks Heidi! This is my third year growing transplants, soooo, I've a great deal to learn.......

Our LFD is around May 5Th (historically) & with our current wild weather, who knows? Not uncommon to see snow in NE Kansas in April & even May. We had snow last May! I think I'll wait a bit, even though our extension calender says to plant in the first three weeks of April........

We do indeed make lots of salsa, but my main focus is having storage onions for as long as possible....