Spring planting is preferred if the job can be completed before summer. In the fall, plant trees and shrubs early enough to allow them to become established before the soil freezes. Established plants take in moisture through root hairs in contact with the soil and will likely survive winter without injury. Another reason to avoid late planting is that trees and shrubs planted relatively late in the fall will be sitting in freshly disturbed soil that will allow frost to penetrate down to the roots, likely causing winter injury.
Many nurseries deliver trees and shrubs with bare roots, though some arrive in containers.
In this article, I will limit my comments to handling bare-rooted trees and shrubs. When the plants arrive, open the bundles to check the condition of the roots. If the roots are dry soak them in water immediately. Place the earth you removed from the trench over the roots and up the stems to provide winter protection. If the soil is dry, apply water.