You should prune a perennial geranium after it has bloomed all season and starts to wither. This helps the plant store energy for the spring while simultaneously keeping it dormant for the winter. This could need to happen any time between August and late October, depending on your zone. Cut perennial geraniums down to 2 or 3 inches above the soil with a pair of trustworthy shears, ideally at nodes or new growth points. Take out any more flowers or foliage. You’ll have a collection of thick stems that is really ugly. But don’t panic, your blooms will return in full bloom the following spring.
