The most important point to remember when learning how to start petunias from seeds is that these are summer, heat-loving plants. It does them no good to plant them early in the garden, as they’ll just sit and sulk or rot. In order to get these seedlings to planting size at the right time, you need to start them indoors at least 10 weeks before planting time. In the north, this is around the first week of March and will be even earlier in more southern states. Although petunias are tough and resilient in the garden, they can be very delicate in the first weeks of life. Start out with a dedicated seed-starting soil mix and new or sterilized planting trays. Of course, you can also start them in eggshells for easier transplanting later. Sprinkle the tiny seeds on top of the mix and gently moisten them with a spray bottle. Cover the tray with plastic wrap to retain moisture and place it in a bright place out of direct sunlight that averages around 75 F. (24 C.). Remove the plastic wrap once the seeds sprout and place the trays under lights in a cooler spot, around 65 F. (18 C.) during the day. Keep the lights about 6 inches (15 cm.) above the tops of the plants. Use water-soluble fertilizer once every two weeks, and water the plants when the soil dries out. Transplant the seedlings into individual pots once they develop two or three true leaves. Lift out individual plants with a wooden stick or butter knife, and transplant them into potting soil.