Maybe this is a stupid question but what do you mean when you say "the proper protection"? Just curious.
Not a stupid question at all but there is no single answer. A lot depends upon your climate, the species of tree and other variables. I don't leave anything just sitting outside unprotected though others in milder climes may be able to do so.
For a Juniper in my area I keep it on the ground and mulched with shredded leaves. When snows arrive I pile snow on the mulch. There is a lot of residual heat in the earth and by insulating it with mulch and snow that heat is trapped and keeps the roots at reasonable temperatures.
I mentioned this somewhere here recently but I checked soil temperature in this very pot and found it to be 34F while air temperatures were 15F, a significant difference.
BTW, I'm sorry to have repeated myself. Sometimes these threads run together and I forgot we already discussed this in your other thread.