Question
We live in the Phoenix AZ area and have a full grown Ash tree in our front yard. The tree is over 30 years old. We recently paid some good money to have a fair amount of dead branches removed and a basic trimming of the tree. I suspect we haven't been watering the tree enough. As a result, we recently added a soaker hose for the perimeter of the tree, but don't really know how much or how often to water. What would you recommend for watering needs of this tree.

Answer
Trees need about 1 inch of water per week. Thee best way is too place a pan under the tree and turn the sprinkler on and when the pan has 1 inch of water in it stop. This is called deep watering.  Since the tree is full grown the root have grown deep and may not need added water except during drought conditions. The use of a soaker hose and continuous water will cause the roots to be near the surface and will harm older tree.