What is causing holly shrubs to drop green leaves on one side?
What Is Causing Holly Shrubs to Drop Green Leaves on One Side?
Certified GKH Gardening Expert
There are many things that could be causing this.
If the side that is dropping is facing a structure, then it may be too little light.
If the side that is dropping is facing out (while the healthy side faces a structure) it may be wind or winter burn, where the wind or cold dries the leaves out causing them to fall. The side facing inward would be protected.
It may be a fungus. Typically, you would see black or yellow spots on the leaves if it was a fungus. A fungicide will help clear it up.