An important factor in tree survival is providing the right amount of water. The first three years are most critical, but pay attention to watering needs throughout the tree's life.
How often and how much? Watering requirements depend on weather conditions, soil type, and soil drainage. The best way to know how often and how much to water is to check the soil moisture at 6 inches below the surface. Water when dry. In the first three years after planting, if the soil is dry provide about 1 1/2 gallons of water per diameter inch of the trunk.
Where? Water the area within the dripline, the area located directly under the outer circumference of the tree branches. This ring around the tree canopy (on the ground level) receives most of the rainwater shed from the tree canopy, and is where the tiny rootlets are located that take up water for the tree. Trees should be watered here, not by the base of the trunk, or the tree may develop root rot. For large trees, focus watering on the area within six feet of the trunk and at the dripline.
When? Begin checking soil moisture and watering when necessary in early spring and continue until the soil freezes.
For additional information, please refer to the United States Department of Agriculture Forest Service Tree Owner's Manual for the Northeastern and Midwestern United States.