I have several young holly plants in a hedge row that are about three years old, grown from whips. Nearly all of them have shown the following symptoms and appear dead:
The leaves have turned yellow/brown, the stem appears grey and mottled. They are grown in a clay soil, in a ridge and furrow field open to the elements.
Could the harsh winter have killed them off? They have survived the previous two winters OK.
Certified GKH Gardening Expert
It is possible that it is holly tar spot. Let me know if this article describes what you are seeing: