I live in So California. I planted 3 pin oak tree's about 4 years ago. They are all doing ok, except there is not much leaf growth. Did I make a mistake by planting these tree's in this area? In driving around our neighborhood, I've seen other pin oaks (although only about 6) doing well. Is the majority of growth going on underground?
Review your irrigation, fertilization and mulching. Tops should be making substantial annual increases in size.
The last couple of winters have been quite dry down here. It would be expected for them not to grow much if they are not getting enough water.