I assume you have planted it in shade...which is what it needs. Then you have to water, water, water. I had a neighbor who set out rootings of hers and this is what she had to do. I thought they would die, but the next year they thrived. This year may be a trial for it but it will probably survive if tended constantly. I don't know how big it was, but a bit of pruning to reduce the stress of transplanting may be in order. Good luck!

Also, hydrangeas tend to wilt in the hot afternoons anyway.
Jayman

Hey, just another thing I've learned along the way. If it gets any sun at all, (which I've learned the hard way that they have to if you want any blooms)...then try putting a big golf type umbrella over them to provide constant shade. This has really worked for me in the past. Might look a little strange but will be worth it. I also learned these umbrellas were a huge help when we pressure wash the house in the Spring. I just cover all my roses, shrubs, and anything else up with these umbrellas. It worked GREAT!!

I know I should prune it back a little, but I don't want to lose the insta-color of all those pretty blue blossoms. I'll just water the heck out of it every day and see what happens.