Many trees and shrubs are transplanted most successfully in the cool months of October through April. However, even the most wonderfully healthy plant will struggle if it is set into an inadequate or improperly prepared hole in the ground.
In the publication "Soil Preparation and Planting Procedures for Ornamental Plants in the Landscape," UGA's Gary Wade says that a big enough hole will be "at least twice as wide as the root ball" and only about as deep as that same root ball.
The temptation is to add compost or other organic amendments to break up the red clay that is in many of our yards. Wade says, though, that all that organic matter "can act like a sponge in the planting hole, absorbing and holding too much moisture and causing the roots to stay too wet."
He says that, instead, it is best to pack the same soil removed from the hole back in around the root ball. Be sure to remove and wires or burlap before planting, eliminate air pockets by watering-in the plant, and apply mulch in a doughnut-like circle around the plant to protect it from weeds and lawn-mower damage.