"You don't say where you live, but boxwoods are marginally hardy in Zones 5 and below, so you might be experiencing plant death because of that. You can sometimes coax them to survive by putting them in a protected microclimate (sheltered from wind, partially shaded from hot sun in the South), keeping them watered prior to winter, and wrapping with burlap in winter. Boxwoods won't take drought, so regular watering and a good soil rich in organic matter will be most helpful.
Luke Miller, editor
Garden Ideas & Outdoor Living magazine "