How severely can I prune rosemary this time of year without killing it? I have two bushes that are both a bit over 4 feet tall and roundish in shape. One is over 6 feet across and the other is over 4 feet across. The centers are brown because of the large size. I want to prune them back because I want to put an herb garden in that area and also to try to keep them a bit neater. However, since I don't want to kill them, I can wait until spring if it would be a more appropriate time to prune them. Any advice will be appreciated. Thanks!