Trees before winter question

So I'd asked this question below in several places. But I never got a response out of it. I hope to pose it here.

I live in a state with ... cold winters and freezing. I want to know how big and how long you have to have young trees or tree seedlings in the ground in the fall before winter to have them still be able to get through the winter? Like... I think they might need to have a certain size and strength right? Or what is your thoughts on this? Is there a certain amount of time they need in the ground first?

Part of the reason I ask this... where I'm at near the Rocky Mountains our July and August are brutal intense summer heat that is very dry and practically unbearable. It makes it hard to keep plants alive if they don't get watered constantly. That is a major disadvantage. Although in a way its a strength because it forces us to think about the principles and basic strategies to get gardening to work.

But it makes raising trees not a good idea until summer is about to end, which prompts this question. And I'd also become very interested recently in trees more and tree farming nursery techniques to study.

Thank you for any insight on this.

Unfortunately, not many responses here either. I had a response prepared but forgot to post it sorry.

I found your question very interesting and did some research on it. Living in a warm climate, I don't have direct experience with your cold Colorado winters.

It turns out there is a lot of info online on your question. I'll summarize what I found:

1) Seedlings (very small trees) benefit from 6–8 weeks in the ground before the soil freezes to establish sufficient root growth to survive winter.
2) Young trees generally need 4–6 weeks in the ground before the soil freezes.
3) Larger container-grown trees can get by with 3–4 weeks but earlier is always safer.

Variety of tree matters in this case also. You have a lot of conifers in Colorado, and they need even earlier planting... while the soil is still around 65 deg F. The thin-barked species (maples, birch, fruit trees) need extra time in the ground also and trunk wrapping. Deep rooted hardwoods tolerate later planting.

Better late than never response? You can decide...but I just touched on the tip of the info that is out there regarding your question.

Thanks very much. That's actually good info.

Thanks to everyone else too.

I have seen rooted hardwood cuttings like walnut or oak that could really use a greenhouse to overwinter in. I think this would apply to seedlings as well. It would be unusual to be sprouting things end of the year but it also depends. Oaks start germinating as soon as the acorn hits the ground but they don't sprout out of the ground and spend all their reserves until spring. So a harsher winter can be bad for weak plants

That said, we would move Japanese maples from the first sign it's going dormant till they start leafing out in spring and that includes all winter, obviously not when the grounds frozen but that's more out of convenience, why dig through ice if you can wait a week. We take grape cuttings and stick them in the ground through that whole season and they will root. Cold could be called refrigeration. The plants are preserved. I think with the seedlings maybe they didn't properly prepare i.e. have enough antifreeze/sugar what have you.

Other things like hardy figs that die to the ground, the really marginally hardy, will not take too kindly to exposing their root system by transplanting. But if it's a matter of in a pot or in the ground I'll take in the ground every time, with the exception of something like onions where the cold is less of a problem than freeze thaw cycles.

That's an interesting idea. So do plants have a plant version of 'antifreeze' chemical?

Thanks for the reply