The way I deadhead petunias is to take clippers and cut the whole plant in half - or even take off two thirds of the growth if the petunias are getting really long and leggy. You can also just snip off about one inch of the old flower and stem but most petunias will bloom all summer even if you don't deadhead or remove the faded blooms. Shortening the stems that have bloomed will encourage more branching and more flowers. Keep growing, Marianne Binetti