Measure from the tip of the geranium stems to just below the third set of leaves. Snip off the stems one-quarter inch above the fourth set of leaves using floral snips.
Cut or pull off the leaves from the bottom half of the geranium stem cutting to expose the nodes, which contain a high concentration of growth cells. Leave a cluster of leaves at the tip of the geranium cutting.
Pot the geranium cutting in a 3 1/2-inch square pot filled with perlite. Press the cutting into the perlite up to the lowest set of leaves. Shake the pot to settle the perlite around the stem.
Drizzle water onto the perlite until it feels moist to half its depth. Maintain moisture at that level while the geranium cutting germinates.
Place the pot in a warm, bright spot for four weeks, or until the cutting shows signs of growth. Cut off the newly emerged leaves for the first few weeks to encourage root growth.
Transplant the geranium into a permanent planter filled with potting soil when roots appear at the drainage hole of the rooting pot.