Petunias are annual flowering plants that bloom from spring to frost. They are available in single and double flower forms, and some blooms are fragrant. They can be used in containers, hanging baskets or in flower borders. Starting petunias from seeds can be difficult because the seeds are very small--between 250,000 and 300,000 seeds per ounce. Once the plants are large enough to be planted in the garden, they are easy to grow.
Sow petunias seeds 10 to 12 weeks before the predicted date of the last frost. Fill potting trays or peat pots with fine potting soil or milled sphagnum moss.
Thinly sprinkle the seeds on the top of the planting media. Press gently in the soil with your fingertips. Do not cover the seeds with soil--the seeds need light to germinate.
Use a spray bottle to mist the soil and seeds thoroughly with water. Cover the containers with clear plastic.
Place the containers in a bright warm spot, between 70 and 85 degrees F. Do not place the containers in direct sunlight.
Petunia seeds germinate in seven to 10 days. When the seedlings come up, move the containers to a bright, but cooler location--between 55 and 65 degrees.
When the first three true leaves appear, transplant the seedlings to small pots and leave in the bright location. Feed every two weeks with a liquid fertilizer following the manufacturer's directions.
When the soil warms up after the last frost, set the pots outside in a shady place to harden up for about a week.
Choose a location with good drainage that receives five to six hours of direct sun each day. Use a trowel to dig holes spaced 12 to 18 inches apart. Each hole should be deep and wide enough to hold the roots of a plant without squeezing or breaking them.
Place a plant in a hole, push the soil back into the hole around the roots with your hands and tamp down firmly. Do not mound the soil up around the stems of the plants. Water thoroughly with a water hose or watering can.