Question
I live in central Ohio, which has hot and dry summers.  I have five riverbirch in the backyard, which I love, but every summer they lose a lot of their leaves.  Once the weather starts getting hot, I usually water them by running a hose to their base and leaving it on a trickle for about 2 hours.  I try to do this to each try about 2-3 times a week.  Is this the most effective strategy (note that I do have a arborist fertilize the trees each year)?

Answer
River birch naturally grow near a water source hence the name river birch. Trees need about 1 inch of water each week. River birch may need more. I recommend that you put a pan under the tree and turn the sprinkler on and when the pan has 1 inch of water in it stop. I would do this for the river birch about every fourth day during dry periods. This will give the roots a deep watering.