The petunia is a popular annual flowers, blooming readily and profusely throughout the summer months. Petunias are easy to grow in flower beds or in containers. They're often grown in window planters and hanging baskets, but they can grow in most containers. Petunias have trumpet-shaped flowers that come in many colors and are divided into two main categories: grandiflora and multiflora. Multiflora petunias have many small flower blossoms and grow in a more compact form, while grandiflora types are trailing, cascading petunias with larger blooms.
Choose a container that accommodates petunias spaced 6 to 8 inches apart. The container should have drainage holes in the bottom.
Plant petunias in well-draining, lightweight potting soil mixed with some bonemeal or superphosphate, according to the recommended dosage on the package. If the potting soil is heavier, mix in some sand or peat moss. Plant the petunias at the same depth as the nursery containers or flats.
Place petunias in full to partial sun where the plants will receive at least four to six hours per day of sunlight. You can set the petunias outdoors during summer in a sunny location or keep them indoors beside a south-facing, sunny window.
Water your petunias when the topmost layer of the potting soil feels dry to the touch, providing water until it begins to drain from the bottom of the container. Don’t allow the potting soil to dry out completely or the petunias to wilt. Take care, though, to not saturate the potting soil.
Feed your container petunias with a high-phosphorous fertilizer, such as a water-soluble 5-10-5 NPK (nitrogen, phosphorus and potassium) formula. Apply the fertilizer once every three to four weeks at a rate of 1 teaspoon diluted in 1 gallon of water.
Pick off the petunia flowers after they begin to fade and finish blooming. Deadheading the blossoms at least two or three times per week will prevent the petunia from forming seeds and keep the plant tidy.