It seems like most plants (perennials, roses,etc.) should be cut back "late winter/early spring", which I guess is right about now. So I just want to confirm that it doesn't matter if buds are already developing or showing, or if there may be a freeze before the warm weather arrives.
Great question. Usually, March is a great month to prune, and it still is, snow notwithstanding. Buds may be nipped by very late bitter temperatures, but that is a function of the temperatures and not the pruning. For example, some plants, such as star magnolia, open very early with a little warm spell, and their blooms often get nipped by frost. Not the fault of pruning. So yes, in that regard it doesn't matter if buds are already developing or showing.
That said, you don't want plants to put a lot of energy into budding and starting to leaf out, only to cut off that part of the plant. Better to prune ahead of that and let the plant put all its energies into what remains. Roses, for instance, should be pruned as buds swell, not after leaves unfurl.
There are two pruning publications on our website in the Publications sectionhttp://extension.umd.edu/hgic/library/publications.