A lady from my hometown in Nebraska writes a daily newsletter. Today she mentioned some trees that were planted 15 years ago in a small town about 60 miles from where she lives. It's interesting to learn that the trees failed to thrive because traditional cautions -- don't plant the tree deeper in the soil than it was in the pot; beware of trees with roots that circle the inside of the pot -- were ignored.
Back in 1994 they planted trees in the park that later became the swimming pool park. Only a few of those trees have really grown right. So two of the state foresters took an air spade and blew the dirt away from the roots of a Norway maple and an ash tree. Both were planted at least 6" too deep plus they were potted trees and had roots that were circling. One root was so large that it had girdled one side of the Norway maple. The ash tree roots had grown up and to within an inch of the surface of the soil and then went out from there. This is a very poor scaffolding for the tree when it is windy. Neither tree was over 12" tall. The maple had stunted leaves and poor top growth. The ash had limbs only on three sides and had set a huge amount of seeds indicating it was stressed and dying. They are going to try leaving only an inch of soil over the roots and then add 2" of mulch and see if the trees are happier. (Source: Email from Carolyn J. Hall, dated 11/6/09.)