Petunias are ornamental flowering plants used by gardeners to provide an abundance of color to a landscape or patio. The more sunshine the petunia plant receives, the more flowers it produces. The petunia needs at least five hours of bright sunlight daily, yet prefers full sunshine for the entire day. The petunia is an annual that begins blooming in the spring, and continues flowering until frost arrives.
While the petunia plants in your garden love full sunshine, if starting petunias from seeds indoors, use indirect sunlight until the seeds begin to sprout. Start the seeds in a container of moist potting soil and cover with clear plastic to create a greenhouse effect. The seeds need a bright, warm area, but not the direct sun. They should begin to sprout in about 10 days. When they sprout, remove the plastic covering.
Until your seedlings are ready to plant outdoors, keep them under a fluorescent light. Place the fluorescent light between 4 and 6 inches above the plant, raising it slightly as it begins to grow. Always maintain that distance between the light and top of the plant. Keep the light on for at least 16 hours a day.
Prepare to transplant the petunias when the danger of frost has past, and the soil is at least 60 degrees Fahrenheit. Transplant the seedlings into individual peat pots when they have three true leaves and fertilize them twice a month with diluted liquid fertilizer. On sunny days, place the petunias outside, to harden the plants, yet bring them indoors for the evening. Do this for about a week.
Plant the petunias in a sunny area. If it is very hot at the time of planting or windy and cloudy, protect the new plants from the midday sun for about the first three days. Once they adjust, the petunias will thrive in the full sunshine, even on a hot day. The petunia will tolerate several hours a day of light shade, yet for optimum flowering, select a sunny area in the garden or on the patio.
Petunias do well in the garden, window boxes, containers and hanging baskets. The two general classes of the petunia are the multiflora and the grandiflora. While the grandiflora produces fewer flowers than the mutiflora, each flower is larger. Some varieties of grandifloras are cascading, well suited for hanging baskets. Multifloras are compact, with more blossoms, and more tolerant to severe rain and wind.