As per wiki, Petunia is a, trumpet shaped, widely-cultivated genus of flowering plants of South American origin, in the family Solanaceae. The popular flower got its name from French, which took the word petun 'tobacco' from a Tupi-Guarani language.
Most of the varieties seen in gardens are hybrids (Petunia x hybrida). The origin of P. x hybrida is thought the be by hybridization between P. axillaris and P. integrifolia. Many open-pollinated species are also gaining popularity in the home garden.
A wide range of flower colors, sizes, and plant architectures are available in both the hybrid and open-pollinated species. 
