According to the Gardener's Network, the majority of petunias are perennials. Annual perennials can survive soft freezes but not hard ones. Perennial petunias come back every year. Check the cultivar to see if your perennial is annual or perennial.
Perennials need full sun and rich, loose soil to grow well. Weed the soil, and add 1 or 2 inches of mulch. Use regular fertilizer when planting them, then re-fertilize them every month. Petunias are not known for having many pest or disease problems in the garden and are generally low-maintenance. They make colorful additions to the landscape as a low-growing flower.