The double petunia is a hardy annual plant that produces two frilly layers of flower petals. Growing petunias takes some care, but the showy flowers are worth the extra effort that they may take. Most varieties available in the 21st century are hybrids that have been bred to be durable and to produce large blooms in many different colors. They will flower from mid-spring until fall if spent flowers are deadheaded and plants are cut back when they become leggy.
Double petunia plants are available in a wide range of colors, including purple, lavender, and pink, as well as white and red. Plants that are small and full are best, as petunias tend to get spindly quickly. For this reason, those that are already in full bloom should be avoided.
Caring for petunias is not all that difficult. They absolutely must have several hours of direct sunlight each day to flourish; those that receive less are likely to be leggy and produce few flowers, or none at all. Exposure to the bright midday sun ensures brightly colored blossoms. These plants also love rich soil and benefit from the addition of compost and commercial fertilizers. Petunias often do best as hanging plants on a sunny porch, as they are easily damaged by rain.
Double petunia plants are sensitive to cold and will not survive frost, but seeds that have dropped to the ground will often sprout and grow the following spring. Those that are grown in smaller pots or planters can be brought indoors and kept in a sunny window during winter. Stem cuttings can also be taken and planted in small pots to start new plants for the next growing season.
Planting petunia seeds takes care as they are extremely tiny. Some seed companies sell pelleted seeds to make them larger and easier to handle, but these also tend to be more expensive. When planting, pelleted seeds should be barely covered with soil, while regular seeds can simply placed directly on top of the soil and kept moist until they sprout. Covering the pots with plastic wrap will keep them from drying out. The petunia seedlings can be planted outdoors when they have at least two sets of true leaves and all danger of frost has passed.
There are several varieties of hybrid double petunia plants. Among the most popular is the series called Madness. These large ruffled petunias can grow to over 2 inches (5 cm) wide and are available in several colors, including a bi-color pink and white.
Another popular variety is the Double Wave petunia. These are similar to the Madness petunias, but have a spreading habit. This gives them a fuller, more luxurious appearance both in the ground and as potted plants. Double wave petunias look especially nice in hanging planters.