Answer: I think you are referring to pinching, or nipping off the very top set of leaves to encourage the plant to branch and thus end up being thick and bushy. You can do this with your thumb and first finger, fingernails or scissors. Trim to just above the next set of leaves. Pinching can also delay blooming so there is a bit of a fine line as to how and when to do it. Full sized tall snapdragons do best when pinched back when they are four inches tall, bachelor buttons and zinnias seem to benefit from a pinching when they have about three sets of true leaves. Salvia, if you have started it early enough, can also be pinched when small. These are all plants that can bloom on side shoots. I have never pinched either godetia (clarkia) or lisianthus, but you could experiment with a few and see how it does for you. In general, petunias, snapdragons, impatiens, chrysanthemums (repeated pinching until July) , marguerites, and geraniums are plants where pinching is highly recommended. Any plant with a central stem and bloom such as celosia would not be pinched.
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