As I have already heard from local nurseries, don't cut anything down until you know what is going on...to do so could send them deeper into shock. Let the plant discard the dead foliage on its own accord.

Here is their message:

"Don't Panic...
So how about the weather these days? Cold enough for everyone? It is hard to believe that Easter weekend's low temperatures were in the high teens. Brrr... I didn't like it and neither did the plants. I saw lots of sheets covering tulips, azaleas, rhododendrons and many other plants in bloom - owners trying to salvage the beginning beauty of spring (photos). We have had many emails with concerns about the way a lot of plants look. Let's not panic. There will be some tender things lost but most everything outside is in shock due to the cold. It will take some time to actually see what type of damage might have taken place. It is supposed to warm up next week so once things start to recover that will be the time to keep a close eye on everything. If it is black it is probably dead. If you are not sure, don't cut it back. There will be plants that will need more time than others so be patient and give your garden a bit of time."