Answer: Petunias develop flowers on new stems. Pinching them back promotes new stem growth and more flowers. Pinching also stops seed production and redirects the plant's energy into making new flowers rather than seeds, which will prolong the blooming. To make a bushy plant you pinch out the growing tips every few weeks when the plant is young. As it matures and branches out, you can continue to promote flowering and branching by pinching out the faded flowers, along with several inches of stem. Everytime you pinch a stem out the plant will develop two new stems, which each have the potential to develop a flower. So your reward in pinching the plants is lots of new flowering stems. I'd use hand pruners or pinch back individual stems with a thumb and index finger rather than run over them with a mower. You'll do a neater job by hand and will have more control over how your plant will grow. There are some new varieties of petunias that do not require pinching. They are referred to as self cleaning. You might try planting some of these types next spring. Enjoy your garden.
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