4. Gently dip the bases into a rooting hormone containing IBA (indolebutyric acid). A light dusting is sufficient—too much will cause the cuttings to rot.
5. Before planting the cuttings, thoroughly scour the containers you intend to use. I favour terra-cotta pots because they allow oxygen to circulate around plant roots, but plastic ones hold water more efficiently. Fill the containers with a sterile, soilless mixture formulated for cuttings and starting seeds.
6. Insert the cuttings into the mix to a depth of about five centimetres and spaced eight centimetres apart to ensure maximum light penetration and air circulation. Place pots in an area with bright light (but out of direct sunlight), and keep the soil evenly moist.
7. After about five weeks, each cutting will have developed several strong roots; repot cuttings into their own small containers.
8. In another one to two weeks, signs of new growth will be noticeable; at this point, move plants to a bright, sunny window. Once a month, fertilize cuttings with a dilute solution high in phosphorus; I like using African violet food (0-12-0) because it doesn't contain nitrogen, which can lead to weak, leggy plants. Keep room temperatures cool over winter—between 10 and 15°C is ideal—and allow plants to dry out between waterings.
9. If cuttings become gangly, pinch them back to encourage bushy growth, and increase light levels using grow lights or fluorescent tubes.
10. By late spring, you should have a crop of healthy, young plants identical to those available at your local nursery. After all danger of frost has passed, harden off plants by moving them to a protected, partly sunny area of the garden. Keep plants well watered for two to three weeks and feed at half-strength with a fertilizer formulated for flowering plants (such as 15-30-15). Transplant the rooted cuttings into your garden as you would any other annual.