Most petunia varieties are considered easy to grow, and they are a favorite of many gardeners. For the plants to thrive, it is best to allow petunia seeds to germinate indoors. To plant petunia seeds, they should be placed on top of well drained soil and watered gently. The containers holding the soil should then be covered with clean plastic and placed in a warm, brightly lit area. Once they have germinated, the seedlings can then be transplanted to a garden.
Gardeners can choose from several petunia varieties. Grandiflora petunias typically have very large flowers, which makes them a very popular variety among gardeners. Mutiflora and milliflora petunias, on the other hand, produce larger bunches of smaller flowers. Gardeners can also choose spreading petunias, which grow quickly and cover the ground with blossoms.
Petunia seeds should be started indoors in most cold climates. They should be planted in the very early spring, roughly four to six weeks before the last scheduled frost. This will give the plants enough time to grow, and they will generally have more blossoms after they are transplanted. To start the seeds indoors, they should be placed in well drained potting soil in small containers or trays.
Petunia seeds are generally very tiny and somewhat delicate. Instead of being placed in a hole in the soil, they should be sprinkled on top of it. A fine spray of water can then be used to water the seeds. This will not only moisten the soil, but it will also partly push the seeds into it. It is important not to water them forcefully, however, since this can cause the seeds to wash away.
Once the petunia seeds have been sprinkled on the soil and watered, clear plastic should then be placed over the top of the container. Some planting trays come with clear plastic lids for this purpose. If these are not available, clear plastic wrap can be used instead. Placing the plastic over the container helps keep the soil warm and moist.
The pots should then be placed in a warm sunny area. They should not be placed in direct sunlight, however, since this can damage the seeds and seedlings. After a few days to a week, the seeds should begin to sprout. Once this happens, the plastic cover can be removed from the container.
Petunia seedlings should be left in the containers until they are large enough to transplant. During this time, they should be watered only when the soil begins to dry out. When the seedlings have three leaves, they can be transplanted into a garden or larger permanent containers.