Sunlight

• Petunias need at least five to six hours of sunlight daily, according to the University of Minnesota Extension, and will produce flowers even more prolifically when planted in full sun (eight to 10 hours per day). Petunias planted in the shade will likely produce a lot of leggy stems and leaves, with fewer blooms.
  
  

Care

• Petunias aren't picky about soils as long as they are well-drained. Digging 2 lbs. of 5-10-5 fertilizer per every 100 square feet of soil gets them off to a good start, with another half treatment applied in July. Liquid fertilizer may be applied every three weeks to container plants. Petunias prefer moderately moist to dry soils. A weekly watering may be sufficient for landscaped petunias, although container plants may need daily watering during dry conditions, according to University of Rhode Island.
  
  

Deadheading

• Pinching off petunia blossoms keeps the plant compact and neat and promotes more blooms.