I suspect that the flowers had merely finished their natural lifespan. (This is a seasonal bloomer, so probably won’t bloom again til next year.) How does the rest of the plant look? Are the leaves green and healthy looking? Does it have any new growth?

@Hollywould: I live in MD and have about a dozen hydrangea plants in my yard (none of which have bloomed yet). I suspect that the plant you have was hot house grown, and “forced” in order to be sold for the holiday. If so, it’s bloom for this season is over. If it’s still green and the stems are holding water, it’s not dead.

Trim it back, cutting off all dead blooms. Keep it watered well until the roots take hold – especially in this crazy heat. You’ll be able to tell shortly if it’s thriving or not.

Transplant shock is the number one killer of new plants. Hopefully you dug a twenty dollar hole for a ten dollar plant, so to speak. I’ve been gardening for years. When transplanting NEVER let the sun touch the roots, that will kill even the hardiest of plants.

Trim it back, give it some good root building fertilizer and wait. Don’t over water it, or the roots will rot from lack of air.

Depends on if this is an “everlasting” or “everblooming” variety of hyfrnagea. It is normal for the flowers to “die” after blooing. Do trim them back and allow the plant to have extra waterings while it’s a Newb to your garden.