Cut off the blooms, they don't last more than 2 to 3 weeks in the best of conditions, and it may put out more....depending on the variety.
Linda C

One reason for blooms dying off is dry roots.

If you just planted out in the past few weeks there is no chance that the plant's roots have made it beyond the original root ball into the garden soil.

And, if the original soil it was planted in happened to have a lot of peat in it, it could have easily dried out - despite being in the ground.

Suggest you get some WARM water (comfortable for your inner wrist skin) and pour it around your plant directly onto the original soil. Go back in half an hour with some cool water and add about a gallon to the soil directly over and around where it's planted. If your local temperatures are high and dry at the moment you'll probably need to water two to three times a week.

If you put a mulch around the plant - a couple of inches thick, six inches wide - and set back a couple of inches from the stems - that will help keep the soil cool and hold in the moisture - plus making a local cool spot.

The other thing to tackle is the excess sun. You could put up a tepee draped with shade cloth to give the shade - or move the plant so it gets morning sun but not hot afternoon sun. It would be safe to do because it probably hasn't come out of its 'pot shape' around its roots. Just keep the ground moist but not wet.