I think it's getting too much sun. They like morning sun, or filtered sun.

way too much sun...your plant is telling you, please let me out of here...this is a mophead hydrangea and it hates hot afternoon sun...I have seen a client of mine placing the hydrangeas on the south side of the foundation wall - have the full blast of the sun between 7 am and 7 pm here in Jersey..and these folks assured me that the plants are fine being there because the landscaping company say it's alright...and I told them, go ahead and water them every morning and hope for the best...and my bet is on the plants will get fried baby fried...I was correct...three weeks later, the homeowner has to call the landscaper back in and replace with another plant...the landscaper insisted on yet another hydrangea - I told the homeowner, only an oak-leaf hydrangea will do alright there...and the homeowner really wanna pink.blue type of mopheads...so she settle with some viburnums with white blooms and berries for winter instead...seriously, some landscaping companies have no clue on what they are selling...you have to do your homework..move that plant to a locale with morning sun and shade between the blazing hrs of 11 am to 4 pm..if you do that, you will never have droopy leaves on the mopheads - unless you dont water them.

My mopheads get sun until about 2:00 and then they are shaded by the house and they are doing very well. The ones that get less sun are not flowering, but they may be too young. The driveway location makes a big difference in your case, I think. A lot of heat reflects of the asphalt. I had some perennial geranium that were a few feet from the driveway that got crispy, and the identical plant only another 3' away is doing fine.

Thanks for all the comments. It's actually several feet away from the driveway but right by a sidewalk. The photo angle is deceiving. At any rate, it's clear that the poor baby won't do well in this spot. Will I damage it further by transplanting it again? I'm reluctant to traumatize it again.

My Hydrangea bloomed beautifully in the Spring then nearly died last Summer in the extreme heat of NY, then we had a harsh winter.
I pruned it down to barely a foot and a half.
Fertilized it and watered it well all Spring .
It grew to about 4 1/4 Feet Dia and was full of beautiful blossoms.
Last week it started to peter-out and wilt, almost as if there were too many blossoms,
It's been hot here so I deep soaked it a few times but it doesn't seem to be bouncing back.
Thoughts, suggestions?
Thanks,
Marc

@annld I would move it to a shadier spot ASAP, as it has not really settled in with new roots yet if you only moved it last week or so. Just keep it moist for the first couple of weeks, expect some transplant shock (drooping for a week or so) and it will do much better once it's settled into a part shade spot. I also moved mopheads all to my shadier back gardens after trying some in the sunnier front. Lacecaps do OK in my zone in the sunnier gardens, but mopheads don't like full sun.

My original post was from a couple of years ago. I did not move the hydrangea, mainly because I didn't really have a suitable spot for it, and it has adapted to the sunny location pretty well. It does wilt a bit on extremely hot days, but I water it well, and it's hanging in there.

Marc, I'm afraid I don't know what to tell you about yours. I hope it recovers.

marc, I'm not sure what the problem is, but when hydrangea start fainting in the heat, I figure that means they need more shade. If I were you, I'd transplant it to a spot that gets afternoon shade and see if that helps.

Kate