>>2534944Zone 2 sounds damn hard. No personal experience, but a few things you can do come to mind.
Earthworks, walls and hardy shrubs and trees that shelter from prevailing winter winds are crucial. Kinda like a horseshoe shape, open to the south, closed to east west and north. Will also catch the sun in spring and warm up faster than flat land would. Extra points for big rock piles that act as thermal batteries.
For a nursery, you can dig trenches that you can cover up in winter. Below soil level will stay slightly warmer and may safe your young trees.
If you dig a bigger whole and put a glass roof on, you got a walipini. If it's big enough, you can put a couple trees in there too.
If you can get an excavator in for a day or two, that should be enough to prepare all these earthworks pretty fast and for not too much money.
Also look into passive solar greenhouses. Particularly from the rocky mountain permaculture institute. That's a little more involved and expensive, but would probably allow you zone 7 plantings inside. They grow bananas and figs up on a mountain in those things.
An attached greenhouse at the south of your house is also a very good idea. Gives you an extra layer of insulation for your home and the greenhouse profits from your heating. With some lights, you can probably grow winter greens continuously and extend you season enough to grow a couple proper tomatoes.
With all your greenhouse options, you can add a woodstove imbedded in a big thermal mass (brick or cob), that you can fire up in the worst parts of winter.
With all plants that overwinter outside, mulch them heavily for frost protection. Like 30cm+ straw, leaf or sawdust. You can also wrap stems and branches of your trees in straw and cloth.
