Well, technically nowhere as the seeds form after the flower is gone. The seeds form down in the ovary. Pic at THIS LINK.

tj

Thank you for the information the reason why I ask was I have this 8 inch pot and it had tiny little green leaves as they grew it look like petunias but don't ask me how they got they I did not plant them but now they are in flower and wow beautiful and in one pot there were as many as 25 plants I have never seen this before now I want to do more next year I fell in love with the 2 tone ones I grow them in 15 inch pots this summer going to collect the seed if I can find them

maybe I will post some pictures of them have to fine them first thank again

Lorna

My wave petunias have reseeded for the past 6 years. Leave the green leaves and let them grow. In another few weeks, you'll be able to tell if your petunias did indeed reseed.

Click HERE to see a photograph of the seed capsule.