I recently purchased an Annabelle Hydrangea and am having trouble with it. It arrived healthy and about three feet tall (in potted container), with blooms already present. I followed planting instructions, nice big hole filled with amended soil; mulched to retain moisture; watered daily except on two days we got torrential rains. Then we got several days of very hot weather (low 90s). It started getting lower yellow leaves first, then stems started turning brown and now upper leaves and flower heads are drying or shriveling and turning brown. What did I do wrong?? Did it get too much water? Too much heat? I dug it up and put it in a large container and brought it inside my screened porch, out of direct sunlight, but still hot and humid. The root "ball" seemed all dry too, but the soil was wet! Can I save it? Should I "prune" it all down and hope it comes back? Any suggestions would be greatly appreciated. Thanks!
It sounds like the soil may not have been well draining.
Here are some links with more information.