You'd probably want to water it every 2-3 days in heat/sun like that, even once established. May not reduce drooping completely but would reduce overall stress.

How much sun is it getting, and what time of day?

The watering part that Springwood_Gardens mentioned is very important and so is mulching 3-4" up to the drip line. I saw some of the hydrangea stock at Walmart on Tuesday Afternoon and the blooms and leaves looked like the poor plants had fainted. God, it was awful. I felt like watering them myself. I inserted a finger into the potting soil of the worst looking one and it was dry, even though the plants were in a partly shaded area. It was a sorry view, something that you expected to see in the closeout 50% section and not in the prime spot that these plants had. Temperatures were close to 100 which made even light winds wilt the leaves... No mulch on those plants but, if you put some mulch (3-4") on yours, it will reduce the frequency of your waterings (and give the surface roots some moisture to absorb and compensate for the moisture lost thru the leaves).

Wilting is usually a problem during the worst of the summer months and is more common during the first few years but, if the suggestions that everyone is giving you do not appear to help, consider transplanting to an area where it gets less sun and less wind. For example, since my temps get into the 100-110s, I try to give them shade starting between 11am. Otherwise the leaves wilt and the blooms can prematurely brown out.

If the soil is moist when there is a wilting episode, the leaves should recover on their own by the next morning. If you see an unusually bad wilting episode, immediately insert a finger into the soil to a depth of 4" (not counting the mulch) and water 1/2 gallon if it feels almost dry or dry.

If the soil feels moist of wet, skip watering and let it recover on its own. Why? Too much watering will result in root rot and this will make the leaves wilt 24/7. Best time to water is early in the mornings (5-6am) and water the soil not the leaves. Amt of water to apply: try 1 gallon per watering - 1.5 gallons if your soil is sandy.

Another reason: the hydrangeas at Walmart also showed indications that they were subject to overhead watering. The leaves had spots where powdery mildew infections had started. Watering the soil instead of the leaves helps minimize this problem.

Last hint: should you notice that only the leaves in contact with the sun are yellowing out completely (leaf + leaf veins too) during the summer, the plant is getting too much sun and needs to be moved or temporarily given more shade until you can transplant it.

Does that help you, PattyW16?
Luis

Thanks so much for the help. The hydrangeas are all mulched well with pine straw. They were placed and planted by a professional landscaper with a really good rep--so I have to hope they are not in the wrong place completely, but my gut tells me they just get way too much sun! I have a couple I planted in another part of the yard and though they are older, they look much better. I did move them from their original location to a shadier spot before they started looking good. The landscaper also convinced me I needed a sprinkler system, which may be some of the reason I have trouble with fungus. I have not used it this year, until last night when I just couldn't stand to see my hydrangeas suffer any more. We have had plenty of rain, with a good soaker almost every week so there was no need. Even with the watering, the flowers did not recover last night. Some of them get morning sun from about 8 til 1. The one in the pic gets it from about 8 til 2:30. I have two others that get it from about 1 til sunset. The guy that planted them kept saying that as long as they were on the north side of the house they would be ok. I wonder ...

Over here that would be too much sun. I equate part shade with a sun exposure of 4 hours or less.

I have several on the north side too but they are shaded by 11am and I still have to apply more water starting in June (we hit the 90s regularly by then and the 100s in July-August). They will still wilt now and then though. There is only so much you can do when the temps are hot. As long as the soil remains moist, not wet, they recover.

Thanks, Louis,
I think I have about decided they need to be relocated, but now I wonder whether it would be worse to try to do that now or wait until fall. Probably 6 of one and half dozen of the other! Good thing I love hydrangeas or I would have thrown in the towel a long time ago!

In my neck of the woods, it is already too late to be planting or transplanting but I had someone overdo the pruning of some bushes and will need to go find some shade cloth for a camellia because it is getting too much sun. A 35% shade cloth might be useful if you can find it. See if any of the local nurseries carry shade cloth and somehow put it above the hydrangeas to give some protection and then transplant them when they are dormant (less stress/shock to the plant).

Hydrangeas are tough; just get as much of the rootball & fibruous small top roots as you can. Since it was just planted in March 2012, there should not be an extensive root system to deal with yet. After transplanting, do not fertilize for a few months. Just mulch it and keep the soil as evenly moist as you can. Probably ok to use weak fertilizers like liquid seaweed or coffee grounds. They contain small amounts of nitrogen and lots of minor minerals. I feed mine with those at least once a year but then stop the feeding by the end of this month so the fertilizers will not prevent the plant from going dormant in the Fall.