It may be too soon to really know which canes are dead. Some people wait until June. Regarding the fertilizer, I'm always cautious. I'm using Osmocote for the first time this year and I have lots and lots of buds. But maybe I would have had buds anyway. I've never fertilized before, but I do use lots of compost as mulch. Whether or not you get any blooms might have more to do with the variety of hydrangea you have and whether or not it blooms on new wood and/or the severity of your winter.

Hello, Just to let you know, I am in zone 7 as you are and I took cuttings from a number of mophead type hydrangeas in approximately early April ( I was moving from a house and took some cuttings to the new house..). These rooted in just a few weeks and have been planted in a flower bed since about mid May. They are now about 1 1/2 feet tall and branched (I did pinch the central leaves two weeks ago to encourage branching). There is no doubt that they will be big enough to bloom next year. I suspect if I had gotten the cuttings sooner, they might have even bloomed this year. Not sure of the variety--they just came with the house. You can't go wrong--I would just keep them in pots until early fall when it cools down a bit, but put them out in your bed in time for them to grow and establish roots this year. They will bloom for you next year, I'm pretty certain. Cheers!

It's never to late to plant hydrangeas. Just plant the new cuttings in the ground, in light shade, mulch it and keep it well watered and watch it grow!

I have never pruned off blooms from any of my hydrangeas on their first year to "help them", especially what appear to be several years old and almost mature specimens like yours. But, they are your shrubs and you certainly can do that. I would only try that with cuttings that are very young, which are tiny and have just one stem. Do be aware of a few things... if your shrubs are of a re-bloomer variety, they may decide to produce new flower buds/blooms. You will then have new blooms in 1-2 months. This type of hydrangea will produce Spring 2017 flower buds around July here in Texas so, any pruning done after June might end up cutting off the Spring blooms you might expect to see in April-May. So be careful with any pruning done to the end of the stems after June. Wilting is just something normal they go thru at first and when the weather gets hot. If this variety is not a rebloomer then this variety produces flower buds once, after June, and pruning in July would mean no flowers in all of 2017.