I am in Zone 4

It looks to me like your petunia is in a micro climate.

" I think I may have a new species!!! Is this possible? "

I think that is highly improbable.

ZM

Petunias are tender perennials in some southern areas but are treated as hardy annuals in colder zones. They won't come back if you pull the plants out regardless and if they have a sustained freeze the plants will die and can then be pulled out in fall or spring. In Z:4 any plants that volunteer there next year will be seedlings from seeds dropped this year.

Young fall grown hardy annuals are more hardy as they get accustomed to increasingly cooler temps and aren't stressed from age. But even they should freeze at your low temperatures so expect that ZM is correct that they are growing in a microclimate keeping the temps surrounding them a bit higher.

Well, that explains why these little volunteer buddies of mine are hardier than the others that I planted. One of the volunteers is definitely in a microclimate as it is about 5 feet from the front of the house but the other is much farther away. Both of them found their home among large rocks.

Those large rocks are exactly what is keeping your petunias alive. The rocks are chemically and physically structured to retain heat. So, the rocks absorb the heat/sun during the day, and then slowly release it all night, keeping the petunias from freezing. I love science! Especially physics and biology.

Martha