Frequent watering is crucial for newly planted trees. Water your tree daily or every other day for the first two weeks. Over the course of a month or two, taper off watering to twice a week as the tree establishes itself. It is very important not to allow the soil to dry out with your newly planted tree. After a few months, the tree will acclimate and routine watering will not be so critical for its survival. As for how often to water after this point, will depend on the climate, the seasons, and the frequency of rainfall. In most cases, a good soaking two or three times a week in the summer months and decreasing to once a week in the colder season should be adequate.