Q: Our 71/2 year old Chinese Pistache tree has always been dense with foliage. In the past couple of weeks, we have noticed that it was not filling out with the abundance of leaves.  Upon close examination today, nothing seems to be wrong with the trunk, or the ground around the roots, yet about 25% of the pencil-thin branches within the inside of the tree have no leaves at all.

A: I think this is yet another example of the tree having been planted too deep originally. If the main roots are buried several inches below the soil surface, weaker roots emerge from the trunk closer to ground level. Summer drought is sure to affect the tree as a result because these adventitious roots are not able to absorb moisture as efficiently as the original roots could.
Pull soil away from the trunk of the tree, keep the area watered each summer and pray that the large roots still have enough life in them to get the water the upper part of your tree needs.

pistache planted too deep

pistache

pistache