When deadheading geraniums, snip or pick off faded blooms using handheld shears or your fingers, though shears are recommended in order to make as clean a cut as possible.
Trim down to the healthiest set of leaves, removing around 4 to 6 inches of stems each session. It's best to deadhead when the weather is cool, and the individual blossoms are dry.
Instead, trim back your cranesbill three times during its growing season: once in early spring as it starts to bloom, again in the middle of summer, and once closer to fall.