Experts and BHG readers answer.
holly leaves turning brown
It's not clear exactly what's going on without seeing the plants, but my guess is that it's winter kill. Winter kill often shows itself in the spring and is a sign that sometime during the winter the temperatures rose for a day or two and then plummeted. Here in Iowa, many people lost boxwoods and conifers because we had a few very warm days in February followed by below zero temps. If your plants are completely brown it's probably too late to do anything but start over."