Experts and BHG readers answer.
dying boxwood shrubs
This is caused by winter kill and it was a common problem across the country this year. You don't say where you live, but the midwest, in particular was hit pretty hard. There's not much you can do to save them. If they are completely brown, they are probably dead. Those with some green may come back slowly. The problem starts in mid-winter when your region experiences a few days of very warm weather which is then followed by a lot of cold weather. This causes the plant to think it should begin to come out of dormancy and then it gets frozen. It often takes a few months for broadleaf evergreens such as boxwood to show the problem, but that's what's going on. Sadly, I lost a number of boxwoods myself this year to the same problem."