You did not say which cultivar of boxwood you planted, but planting one that is reliably hardy in this area will minimize the chances for winter damage. Wintergreen boxwood (Buxus microphylla var ...

Most types of boxwood shrubs are cultivars of either Buxus sempervirens, also known as common or American boxwood, or Buxus microphylla, better known as Japanese boxwood. Other boxwood varieties ...