Petunias are a cool temperature annual in Arizona, although technically a perennial, they cannot handle our Summer time heat. They can vary from shrubby to trailing, large flowers (grandiflora) to small super bloomers ( multifolra). They like well draining soil and full sun in the cooler months, prolong their life by moving into a partially shaded area in our hottest months. Dead head spent blooms to encourage more blooms and to prevent them from tangling up the new buds trying to grow.