My Myoporums get dieing
 

I live out here in the Phoenix area and I have about 95 Myoporums to cove
the gravel which is mandatory where I live. I don't know if I'm over or
under watering them or planting them in a big enough hole with enough mulch
because the ground is rocky. But I'm losing about 25 to 30 % of them and I
just keep re-placing them. Anyone has as ideas how I should treat them this
time of year?

Richard