Sorry it took so long. The day was so beautiful! Once I got outside I didn't come back in until I got hungry! What I was going to say was recently I acquired almost 3 year old plumeria seedlings. They were yanked out of the ground before I got there, and not very carefully either. I was going to just keep them bare rooted for the winter. But local plumeria consensus said to put them back into pots on a heat mat to help the root systems recover during our warmest days we have left. Here are what my 18-30", 3 year old tree roots looked like. I do believe they had a chance to be bare rooted but they were just this side of considered too young to winter over this way.
I believe your young trees would not have a root system established enough to survive the winter out of a pot. My suggestion to give them the best chance is to put them up off the ground on to a table of sorts. Provide heat by way of a heat mat (Amazon)to keep the roots warm. If they are not indoors, then erect a structure outside, a hoop house, or a tent, or greenhouse that will protect them from frost and cold weather if possible. It is believed that a first year seedling should not go dormant. Mine have gone dormant and knew no difference. But that is the general consensus speaking again.
Good luck this winter. Keep us posted.
