Pile your trees close together and mulch them with leaves, straw or commercial mulch. You could dig a shallow trench if you're really worried or won't be planting anytime soon. As long as they stay moist, your trees can wait all winter if necessary. I live in an area that produces most of the nursery trees and shrubs for the Southern US. Farmers dig and B&B starting in December and pile the trees up in the fields and nursery lots mulched and insulated just like this until they ship in the spring. Good luck!