As you might expect, water is an important element of the health of an apple tree and water plays a major role in the development of the fruit of the apple tree. Not only is the proper amount of water important, but how that water is delivered also makes a difference in the quantity of fruit that sets and in the size and flavor of that fruit.
Start watering early in the season, before blooms appear on your trees. Build basins around your trees that extend as far out as the branches on your tree.
Fill each basin with at least 5 inches of water, three times each week. Continue with this watering pattern until blooms set on your trees.
Water your apple trees for 4 hours at a time, at a rate of approximately 4 to 5 gallons of water per hour when blooms set and while apples are growing. Water for 4 hours at a time, three times per week, until apples begin to ripen.
Cut back watering to once or twice per week once the harvest begins, as the trees will require less water at this point.