Hello, Anna5. It would start to bother me by now if it has not leafed out yet but some people have reported leaf out on new hydrangeas as late as the end of this month. If the roots are still alive, it should leaf out very soon. You can plant it outside if it is hardy to your zone. A location that provides shelter from the afternoon should work well. Pick a spot that gets afternoon shade and cover it with 3-4" of mulch. Maintain the soil evenly moist (no periods of dry followed by periods of too much water for example). If the soil feels dry when you insert a finger to a depth of 4" then water (1 gallon). If your soil is alkaline, you may want to amend the soil now and then using products such as garden Sulphur, green sand, aluminum sulphate or liquid chelated iron compounds found in almost all nurseries.

You can prune the spent blooms by cutting the little stem that connects it to the stem. Being so late, I would also try pruning the stems in 1" or 2" increments from the end of the stem to the bottom; stop pruning if you hit green or get to the bottom. If all stems are dry, it may be a goner. In that case, I would place it outside for maybe one or two more weeks, watering it as needed. If it does not leaf out by the end of May then put it in the compost pile.

If it does not leaf out, it may have dried out. You can try again with another hydrangea but use the finger method to help you determine when to water. I hopoe it makes it but this late in the year, I get pessimistic about its changes.

Good luck, Luis!