Question
We live in Maryland and earlier this summer we had a row of mophead(big leaf)hydrangeas planted along the southeast side of our house.   They receive morning sun and are in the shade starting around 4pm (basically 9 hour of sun).  They wilt in the afternoon and their leaves are curling up and turning brown.  I have been deep watering every other day because I read that these plants can get root rot with over watering.  The soil is clay with couple of inches of top soil and 3 inches or so of mulch.  Is this too much sun for this type of plant?  Sounds like hydrangeas are finicky when it comes to sun light.  Once they mature will they stand up better to the heat?  Should I water more often until established?  I would hate to move them and it is late in the summer for that. If they need some shade from another shrub/tree could you recommend one please.  Currently the beds look like this.  3' beds with side walk on one side and house on the other.  They are planted 3'6'' apart and there are 12 of them along the side of the house.  Is there a tall shrub or small tree that could be planted every third one or so that could provide some shade from the hot mid-day sun?  What I worry about there is issues with roots cracking the foundation and the sidewalk over time.  Also, I do not want to make the hydrangeas compete for water.  Any recommendations or advice would be appreciated.  Thank you.

Answer
Kevin,

This paragraph was taken from the United States National Arboretum's website. I think it will answer your question.

Hydrangeas grow best in moist, well-drained soil. Most hydrangeas benefit from some shade, especially in hot climates. Bigleaf, oakleaf and smooth hydrangeas will usually perform well on the north side of a house or planted at the edge of a woodland.  As discussed earlier, growing hydrangeas in deep shade is not necessary and can greatly reduce flowering.

The amount of sun that hydrangeas can tolerate depends on species, climate and availability of water. Panicle hydrangea tolerates more sun than do other species. Plants grown in hot climates require more shade than do those grown in the colder limits of adaptation. In southern climates, providing frequent and adequate watering will allow hydrangeas to tolerant more sun than if they were subjected to moisture stress.

They also could be going through some transplant shock. I would recommend amending the soil by augering holes around the plants and filling them with sand. This will gradually change the texture of the clay soils and allow for better drainage.

Good luck,
Ed Gulliksen