If you don't remove the whole stalk, the faded flowers will start to go to seed. When you remove the stalk it encourages the plant to keep blooming, although there are some varieties that you don't need to remove them for. Some ivy geraniums will drop the flower stalks on their own. I don't remove mine until the last flower falls from the stalk. There's really no need to remove the individual flowers before the stalk has finished blooming. Sometimes I'll let a stalk go to seed then pick it and let it dry out but most of mine are grown from cuttings. Good luck.

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