Answer: I think the reason that you're getting conflicting advice is that some petunia varieties are "self-cleaning", which means that the old flowers will fall off after they fade and you won't need to deadhead. Older petunia varieties benefit from being deadheaded. I pinch off the faded flowers plus some of the stem - this encourages additional branching and additional flowering. Even if your petunias are the self-cleaning types, you can still pinch off the faded blooms - it won't hurt the plant - and it will encourage lots of new flowering stems.
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