Transplant shock, a reduced root system, hot summer temperatures, wind and root rot can all mix together or cause wilting just by themselves. Hydrangeas wilt during the day. Assuming the soil remains moist, they should recover on their own by the next morning. Once established in your garden within 1-2 years, the wilting episodes should be reduced. But you may still see some during the hottest days of the year.

If the wilting episode looks extreme, add about 1/2 gallon of water starting near root ball and extending outwards. Otherwise, add 1/2 gallon of water if the soil feels dry or almost dry when you insert a finger to a depth of 3-4". If the soil is moist or wet, do not water. Resume normal watering as originally scheduled (add 1 gallon of water).

To prevent root rot, do not water of the soil feels wet.

Luis

QF's should not wilt or droop much at all in full sun, as long as they are adequately watered. In fact, there is no hourly limit on the amount of sun these can take (mine gets 12 hours). If yours is new, I would water it twice weekly. Usually holding a hose spray nozzle on "shower" directly on/around the root ball for up to 1 minute will do the trick. After this, unless in a drought, panicle hydrangea should need little if any "manual" watering.

Even though big box retailers sell panicle hydrangea (e.g. Proven Winners, Monrovia, etc.) all summer long, it's recommended that most hydrangea be planted in the spring or fall to have time to become established so heat doesn't affect them as much.

As long as the plant does not die (which is unlikely anyhow), winter will serve your QF nicely, as it will establish itself in the spongy ground (as long as your area gets enough rain/snow), then reward you with blooms on *every* new stem next season.