I have been propagating geraniums using the same “mother” plant for many years.
1. Get a see-through container (to check how quickly the roots grow). The size of the container depends on the number of cuttings you intend to make. I wanted plenty so I used a wide plastic container. I will add more as and when my plant makes more shoots. I lined the inside of my container with clingfilm so I won’t need to clean it afterwards and filled it with water.
2. Prepare the cuttings, leaving two leaves and cutting right underneath a node. The mother plant needs to be fed a couple of weeks beforehand to encourage new shoots.
3. Cover the container with a double-thickness length of aluminium foil (this gives it more strength), pushing the foil tightly around the edge of the container. Make a small cross with a sharp knife just large enough to fit the stem through. To help the cuttings stand straight, I used cardboard from an egg box… …but the cuttings were still wobbly so, I decided to use some BBQ wooden skewers. I sellotaped a small length of cardboard on either side of the container and cut a little slit wide enough to hold the skewers in place (I will add more as and when required).
4. Place the container on a window sill away from direct sun light and wait for a few weeks for the roots to grow (make sure the bottom of the cuttings is always in water of course). You will know your cuttings are growing because new leaves will appear. Remove any flower clusters if they appear as you want the plant to use its energy making roots at this stage. Then, place the new plant in a pot with compost whenever convenient.
The advantage of this method is that you don’t waste time planting a cutting that might die.
Tip: buy a geranium when the selection of colours and type is wide. Feed it throughout the summer and bring it indoors before the first frosts. Trim the branches to about one third of its size (it will take less space on your window sill!). You now have a “mother” plant for the following spring.