This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
Like some other plants, Tricolor Pelargoniums will grow in almost any soil; but that best adapted is a combination of two parts of light fibry loam, broken up into small lumps - one part leaf-mould, the other part composed equally of well-decomposed horse-droppings and river-sand. I am proceeding on the assumption that the cuttings put in some time previously are ready for potting.
Supposing the cutting plants are strong, and ill small 60-pots, the shift should be made into pots fully two sizes larger. The operator should commence by crocking the requisite number, giving double the quantity of drainage usually afforded other plants. The pots should be scrupulously clean. A little fibry material from the soil should be placed over the crocks, then some fine soil. The plant should be carefully turned out of the pot it has previously occupied, the crocks removed without doing damage to the roots, the plant placed in the new pot, and the soil pressed firmly about it. Where perfect drainage exists, firm potting is of great importance; it prevents a too free evaporation of the moisture in the soil on sunny days, sustains the plant for a more lengthened period, and saves the trouble of continual drib-blings of water, which not only consume time, but are also hurtful to the plants. If the potting compost be at all damp, no water need be given after potting. It is a good plan to thoroughly soak the plants that are to be potted with water the day before being shifted into the new pots.
When this is done, eight or ten days after potting will be a good time to administer water for the first time, as at this period the roots will be finding their way into the new soil that surrounds them. When water is given, let it be given abundantly, and not a mere surface sprinkling. The temperature of the water given should be about 60°.