KINGDOM: Plantae
ORDER: Solanales
FAMILY: Solanaceae
GENUS: Petunia
Petunia is a genus in the family Solanaceae, subfamily Petunioideae. Well known members of Solanaceae in other subfamilies include tobacco (subfamily Nicotianoideae), and the cape gooseberry, tomato, potato., deadly nightshade and chili pepper (subfamily Solanoideae). Some botanists place the plants of the genus Calibrachoa in the genus Petunia, but this is not accepted by others.
Thanks Wikipedia