Moving trees into a green house

Its about 1C outside right about now, on average, and my trees are under about 1 ft of snow. If i wanted to bring them into a green house could i just stick them in a heated one and let them go, or should i bring them slowly. Maybe put them in a cold frame for a bit before turning on the heating.

This may seem like a criticism but it isn't; I'm just curious to know why you'd want the greenhouse heated. Reason I am asking is simply that at this time of year I am trying to do the opposite. Apart from the few that remain outdoors, mine have been either in the cold garage all winter and I am now trying to get them "hardened off" again by putting them into the cold greenhouse (mostly to shelter them from the strong winds we have been having recently) or outdoors into a plastic cloche type greenhouse.  In my case it is about getting them the longer amounts of light this time of year brings and letting them wake themselves up in their own time.

As I say, I'm just curious as to why yours go from having spent the winter outdoors to a heated greenhouse. I'm really just nosey about how other folk cope with real proper winters and not these sunny Florida things.    * 

ps - temperatures here in Scotland at the moment vary from about 3C to 10C, we are still prone to frosts right up to June, and even when it gets to its "hottest" it is unlikely to exceed mid-20s C


*  that was a little light-hearted comment and I am very aware that southern weather has not exactly been gorgeous this past winter.

I ask because we have a very short growing season here, buds usually pop early-mid may. I wanted to bring them in to extend the growing season in a sense. Once the temperature comes up enough they would be going back outside. As for winter protection, it interests me as well, all of my outdoor trees are in large pots or pond baskets so i just leave them where they are and shovel some snow in around as soon as it comes. The exception is any weak trees and my cypress's, they go under my deck just enough to stop a large amount of snow build up from peeling the branches like a banana. Once i have a few trees in shallow pots i plan on making a poly tunnel and mulching around the pots.

Thanks. As I said I was just interested in how folk do things. We have a fairly short growing season too; we're at least two weeks behind people in England (probably three behind those in the very south of England) and our autumn starts far sooner too. We do have the advantage of approximately an hour or more additional daylight though in the height of summer.

Everyone's got at least one good thing about their climate   . We get a lot of rain here all spring most of summer and the fall hahah. I've been using 100% inorganic soil on all my trees since last year and i'm rarely worried about them drying out. The big downfall is the cold current coming down from Labrador keeping Newfoundland rather cold well into spring. One day i dream of living somewhere where i can re-pot my tree in February or March instead of May. I'll keep dreaming 

I would start by moving them into an unheated greenhouse. Then, once it's warm enough outside, put them out

If you have a greenhouse, why not turn it into a cold winter storage facility? Unless you actually grow warm stuff in there in the winter... I have a greenhouse that I use for storing my trees in the winter, temp. controlled to keep dormancy, but I get about an extra month on each end of our fairly short season here. All my trees are repotted and almost all in leaf right now. That's a few weeks ahead of where I would be otherwise. Also as I use heat mats I get good root growth during the fall and winter.

i neglected to mention that i don't have a permanent green house yet. I have one of those crappy plastic ones you set up. It would be destroyed during winter if i left it out.