Calibrachoa x hybrida, or Trailing petunia, is a tender perennial, usually grown as an annual, that has been known to survive the winter in USDA Zone 7, but is more commonly winter hardy in Zones 9 through 11. The plant grows best in moist, organically rich, well-drained soils in full sun. It can grow in partial shade but flowering will be reduced. The plant also tolerates drought and, unlike most other petunia-type plants, Calibrachoa does not decline during hot summers.  It does require a slow-release fertilizer incorporated into the soil and a diluted liquid fertilizer every few weeks throughout the blooming season.