An African violet (Saintpaulia) should be potted in light, well-aerated soil for good water and mineral retention. Amateur growers generally prefer soilless mixes, containing a large proportion of peat moss and not requiring any sterilization. Otherwise, the conventional mixture is made up of one part soil, one part peat moss and one part sand. After the various components are mixed, lime must be added to correct the soil’s acidity, and bone meal, to provide a source of organic phosphorous. If you use soil from your garden rather than potting soil, you should sterilize it in an 82°C oven for at least 30 minutes to eliminate any harmful organisms.
Containers and repotting
Plastic pots are suitable and seem to be the most popular for growing African violets. With clay pots, fertilizer salts may accumulate around the rim. Any leaf stems resting on them will develop spots and eventually rot.
An African violet can live for years in the same pot, which should normally be 6.5 to 7.5 cm in diameter. The plant's spread should be at least three times the width of the pot before it is repotted. Wait until spring to do so, and then place the plant in a pot that is just slightly larger than the original one. Many people who have trouble getting their African violets to flower are simply growing them in pots that are too large. Because the petioles, or leaf stems, are quite fragile, it is best to let the plant dry out somewhat before removing it from its pot.