Few days ago it was just about right time to put all trees down from benches and provide them protection from wind and frost. I used wood sawdust to cover all trees from top. They stay like this outside till March next year. All are local to my climate so they can handle temperatures below -20 C. I think biggest danger for the trees during the winter is drought. So when they are covered with sawdust they stay moist and even strong winter winds will not dry them out. Whenever we will have some snow I will shovel it over the trees.