Petunias (Petunia x hybrida) are annual flowers that work well as a border, along walkways and in hanging baskets. Once the petunia plant starts blooming, the plant should continue to bloom the entire growing season. The plant will stop producing flowers if the dead flowers remain on the plant. Petunias will create seed pods at the base of the dead flowers unless you remove the spent bloom. This process is called deadheading.
You can remove the dead flowers with a pinch of your fingers. Simply snip the stem that holds the flower just below the base. If you just pull off the dead flower, the plant will form a seed pod at the base. You must remove the base so the plant focuses on generating more blooms.
If you wish to collect seeds from the petunias, wait until the growing season is almost over and allow the last of the blooms to go to seed. When the seed pod swells and turns brown, remove the seed pod from the plant. Dry the seeds completely before you store them for the winter.
Your petunia plant will grow and produce a mass of color all summer long if you deadhead the spent blooms as they turn.