Here in Texas when we dropped from sustained warm temperatures in the 60s to -2°F overnight, many of these shrubs suffered major injuries. After this shock, it is best to just water mulch and wait to fertilize after the shrub shows leaf out of new growth. Since it is growing from the base, allow it 2+ months to leaf out from existing branches or simply wait until the fall. If no growth by then, feel free to prune dead wood. Lightly scratching branches can also tell you if a branch is alive but not if the roots are alive. I try to mulch them and water deeply going into this type of weather but had to replace some of them.
