My petunias just keep rotting I don't know what to do. My dianthus also rotted last year, but this year as soon as I see the rot symptoms I dig them up and rinse them with bleach. Both the petunias in the ground and in pots rot. And there is no way I water them too much, last year was the worst drought in Texas history. Oh and the bleach so far kills the already dying petunia. Symptoms: Wilt, hollow, stems, death.
It sounds as though your petunias may be suffering from a root rot fungal disease. In order to diagnose which one specifically you may need to take a sample to your local cooperative extension service office for them to submit to the Texas A&M plant pathology lab.
The best sample is a plant that is just beginning to show symptoms rather than one that is completely dead already.