It could very well just be transplant shock - the beginning of August is a less than ideal time to plant much of anything across a good portion of the country. Planting in a full sun location just compounds that effect. I'd also question the advisibility of adding Soil Moist or other polymer crystals to the planting hole. These are too easy to overdo and they may be holding excessive moisture in the root zone - too much is just as bad, if not worse, than not enough. The addition of fertilizer may also be contributing additional stress. It is not recommended to fertilize plants immediately at the time of planting.

I'd suggest you dig down and examine the soil at the root zone. If it is not overly moist, then transplant shock is most likely the cause. Just keep the plant well watered (but not overdone). It should perk up when temperatures moderate and will be fine next season.

i'm inclined to think that the problem with your limelight might have something to do with the soil moist? i've never used it, but it doesn't seem like this plant is that sensitive otherwise.

my limelight is 2yrs + old and has taken so much abuse that i am amazed that it blooms the way it has. it sat in a pot it's first summer, repeatedly wilting and bouncing back, then i threw it into a badly dug hole out of desperation to overwinter, then had to be dug up and sit in a big bucket for several weeks thanks to cleanup from a terrible storm. (the tree trucks and phone company trucks needed access thru our yard and the plant was in the way.) it finally got it's permanent home last fall, after i trimmed off all the branches that got broken, and is blooming beautifully as i type, again! maybe i've just been lucky, but it never even got so much as one yellow leaf through all the abuse it took.

if it were me, i might pull it back out and try to get rid of the soil moist, then replant it, keep it watered and hope for the best.

Hmmm, well, I've used Soil Moist before on other hydrangeas, and I found it helped immensely in terms of retaining enough moisture to keep the bushes from wilting, and after three years those Annabelles are thriving. However, this jar of SM had fertilizer in it, though, whereas the other jar of SM I had didn't, so maybe it's the fertilizer that's the problem.

I think I'll take your suggestion and dig it up this weekend and try to get rid of as much SM as I can and then re-plant, should be easy enough to do since it's only been in the ground a week.