Answer: Petunias are naturally sticky - when you pinch a stem to deadhead, you'll feel the stickiness. But, excessive stickiness can be the result of aphid feeding so you'll want to closely inspect the undersides of the leaves for evidence of these pests. A second possibility is that your plants are growing beneath a tree that's periodically infested with aphids. These pests feed on the fluids of the leaves and exude a sticky substance called honeydew (for obvious reasons). Aside from that, expect the stems and leaves to be naturally sticky.
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