Pelargonium peltatum is a trailing, ivy-like species of geranium. Geraniums are easy-growing, pleasant plants that do well in indoor or outdoor environments. Geranium owners know this better than anyone -- once you grow and raise one, you almost always want more. Luckily, trailing geraniums are easy to propagate by seed. The small seeds are easy to harvest, but you have to be careful not to loose the tiny seeds before its time to plant.
Collect the small round seedheads when they begin to become brittle and dry. Pick them off by their slender stalks or cut the main (former) flower stalk at its base with pruning shears. Hold a paper bag underneath the flower stalk as you prune or harvest the seedheads to avoid losing any.
Keep the paper bag in a sunny, dry spot until the seedheads open to reveal the tiny seeds inside.
Collect the small seeds from the bottom of the bag. Sow them immediately, or store them in a seed envelope. For long-term storage, place the seed envelope in a sealable glass jar next to a packet of silica gel. Keep the seeds in a room-temperature spot away from direct sunlight. When stored in this fashion, they will last up to one year.