Your soil is always wet--there's your problem, and you are right they can't take up the water when they are waterlogged.. Some survive because maybe they are a little higher or are somehow not getting as much water and the ones in a slight depression.

A petunia that is getting too much water looks fine until one day it just seems to collapse and die. Cut back on the water and they should all thrive.

Thank you so much for your thoughts.

I think I might have been misleading when I said the soil was always wet. I didn't mean it was ALWAYS wet, I meant whenever a petunia wilted the pot wasn't dry, so I know it's not from lack. But I don't keep the pots continuously wet. What's even more mystifying is that I can have 2-3 plants in a large bowl, and only one will suddenly wilt.

Still, your comments have made me think. I will definitely pull back a little on the watering and see if this helps.

Thanks for your insights.

Just make sure that when you DO water, that you do so thoroughly.

But...isn't there a condition or disease all petunias get called boytrous(?) rot that not only makes them wilt but also makes them sticky to the touch over time? It happens to mine every summer,and I do pick the wilted ones off! Is there anything I can spray them with for that,either natural or chemical?

Petunias are sticky even when they're healthy.

my petunias are the same .one day they look great the next they are wilted and need to be pulled out! yuck, always buying more...

Suggest you all Google Boiytrous rot!