The petunia is one of the oldest common ornamental flowers. It was introduced to Europe from Africa in the beginning of the 19th century. Since then, many varieties have been produced to suit any taste. While widely used in landscaping, petunias are particularly well-adapted to container life. They are an ideal choice for well-lit areas, such as hanging porch containers and window boxes.
Petunias can be potted for eventual transplantation or they can be planted in the container in which they will spend the year. The early development of petunia plants can be quite slow, so start them two-and-a-half or three months before the last frost. The exact starting date varies depending on your location, but for most, it should be around early March. Petunia seeds are extremely small and can be difficult to see and plant. The best method is to press the seeds into the potting soil with your fingertip. They should rest on the surface of the soil as they require light to germinate. After a week or two away from direct sunlight, seedlings should become evident and you can place them in direct sunlight in a window. After the last frost has passed, you may move your containers outside.
An incredible number of cultivars are available, but only four main types of petunia plants. Spreading petunias are normally low ground plants that have abundant growth that will dangle attractively in a basket. Grandiflora petunias have large eye-catching blossoms, and it is the trailing type that does well in hanging pots, while the standard type of grandiflora does best in a window box or pot. Milliflora petunias are also best suited for window boxes, and have extremely small blossoms in great quantity. Multiflora petunias have blossoms that are intermediate in both size and number when compared to milliflora and grandiflora petunias and are preferred for window boxes as well.
Petunias in pots require frequent fertilization, and to accommodate this, you should use a mix of fertilizer in water once every two weeks. They do best when they receive lots of direct sunlight daily. Mulching keeps the amount of weeding you are required to do to a minimum and helps the soil hold onto moisture. Do not water daily, but check often to make sure that the soil has not dried out. During the blooming period, you have to deadhead. This is the process of removing old, dead blossoms from the plant so new ones have a chance to form and is only required for multiflora and grandiflora type petunias.
Most petunias have been bred to be disease resistant, but a few issues of concern still remain. Petunias in pots are vulnerable to attack from flea beetles and whiteflies, which consume parts of the leaves. Treat with insecticide, and try to keep petunias separated from other members of the nightshade family, such as tomatoes. Prevent fungal infections like botrytis and damping off by watering at the soil level rather than above, and use sterile soil and pots. Ensure that the pots and soil mix you choose are of a type that drains well, as too much moisture leads to rot.