Be sure to consider site conditions when selecting a tree. Choose small trees for small areas. Place large or tall-growing trees in areas where there is plenty of room for the spread of roots and branches, and where the trees will have room to grow to maturity without severe pruning. Decide what function the tree should have, such as shade, windbreak or accent. By knowing the conditions the plant must meet, it will make your choice easier.
Most trees have a shallow spreading root system with a few anchor roots.
University research shows that tree roots grow within the top two feet of the soil and spread well beyond the drip line of the tree. Till the soil in the planting site 4-5 times the diameter and no deeper than the root ball. The edges of the excavated area should be rough and sloping. Tilling soil will improve aeration and root growth. In the center of the tilled area, dig the planting hole twice as wide but only as deep as the root ball.