A main reason for tree decline is planting too deep. Burying a tree's root collar can reduce growth, cause defoliation, leaf yellowing, the gridlocking of roots, and the death of a tree.
It may seem wise to dig a hole the size of the trees ball width. but digging a hole that is too small can stifle growth and the development of roots leading new trees to become more unstable and blow over easily in storms
Summer and Winter are the worst times of the year to plant trees due to their extreme temperatures which cause stress to trees making them susceptible to pests and diseases.
A majority of plants die from overwatering than not enough. In clay soil, water can often suffocate trees or cause it to dry out in the hottest parts of summer.
A good thing to always remember is to never dig the planting hole deeper than the height of the tree's root ball.
Always dig a shallow hole that is two to three times wider than the root ball so that the tree can have room to grow and expand.
Planting during the Spring or Fall are great times because of the mild temperatures, warm soil, and little temperature transition between night and day allow a tree to grow with few stressors.
Water your tree infrequently, slowly, and deeply allowing for longer and longer intervals to pass as the tree matures and develops. Water your tree every day, then every other day, then once a week, and so on. Remember to water your tree during dry spells and especially in the winter. Your tree may be dormant, but it still needs energy. As well take into account the type of soil that the tree will be planted in and how well it absorbs water.