How Often and How Much?
Frequency depends on soil drainage. Soils that drain quickly will require more frequent watering than those that drain slowly. The best way to know how often to water is to check the soil moisture at 6″ below the surface.
First 3 years after planting: If the soil is dry, provide about 1-1/2 gallons of water per diameter inch of the trunk.
All other years: Because soil type and weather conditions influence the demand for water, irrigation schedules and amounts vary.
• Tree Roots Need Oxygen.
Soil saturated with water for more than 24 hours can prevent roots from getting oxygen, Therefore, watering too much is as dangerous as watering too little (and hard to correct).
Water the area within the dripline. For larger trees, focus watering on the area within 6′ of the trunk and the dripline.
Start checking soil moisture and watering when necessary in early spring, and continue until the soil freezes.