Petunias are an annual flower that blooms late spring until the first frost in fall. They come in nearly every color imaginable, and each plant produces a profusion of flowers. They work well in garden beds, in borders and in containers on patios and balconies. They are disease and pest resistant and require only minimal maintenance in order to thrive. Pruning helps control both the height of the plant and encourages further blooming throughout summer and into fall.
Pinch off the top of each stem after transplanting outdoors. Grasp each stem between your thumb and forefinger one inch from the top and pinch it off. This encourages branching and leads to a bushier, fuller appearance.
Cut back the petunias at mid-summer once they begin to become leggy and flowering slows down. Cut each stem down to half its height with sharp shears, making sure to leave at least one set of leaves on each stem after pruning.
Fertilize with a balanced liquid fertilizer after cutting back to encourage quick growth. Water thoroughly after fertilizing so the roots quickly gain access to the new nutrients.
Deadhead the spent flowers from the large blooming petunia varieties throughout the flowering season. Pinch them off one-fourth inch beneath the flower head as soon as the petals begin to wither. This prevents the formation of seed heads and leads to further blooms.
Continue deadheading until the plants cease blooming in fall and begin to die. Remove the plants from the beds and discard them at this point so the bed is read for next year's petunia planting.