Potting African Violets
Many successful growers of African Violets recommend repotting with fresh potting soil, twice a year. At the very least, an African Violet should be repotted if the soil has been the same for over a year. The accumulation of salts from fertilizer and natural chemical processes alter the soil PH over time, leading to less flowering.
You can re-pot an African Violet in the same size pot or a slightly larger one. Don't go more than a few inches larger than your original pot. Violets like fairly shallow pots and excess soil which doesn't drain may harbor deadly root-rot.
The process of repotting an African Violet into a larger pot is called potting up, it is very easy to do and takes very little time. One of the most commonly used methods of potting up is called mold potting. While the method is very simple, it also minimizes the potential of shock caused by repotting.
Your first step is to select an appropriate pot and a good potting soil. After you have done this, take your new pot and put enough potting soil at the bottom to compensate for the difference in height. For instance, if your current pot is 2-1/2 inches in height, and your new pot is 3 inches in height, then the difference in height is 1/2 inch. You will, therefore, need to put 1/2 inch of potting soil at the bottom of your new pot. (Note: As you prepare your new pot, keep in mind that the final soil level should be about 1/2 to 3/4 inch below the rim of the pot.
After you have put soil at the bottom of your new pot, remove your African Violet from its current pot. To do this, simply place your hand over the top of the pot so that the crown of the plant is between your fingers. When doing so, be careful not to damage any of the leaves or stems. Next, turn the pot upside-down. If the pot is plastic, you will only need to push on the bottom of it to loosen the rootball. If the pot is clay, gently tap on the bottom of the pot to loosen the rootball.
Once you have finished repotting, you many want to bag it. Many growers recommend this, asserting that the increased humidity helps African Violets recover from any transplant shock. To do this, place the African Violet into a clear, plastic bag which is large enough to accommodate the plant without damaging the leaves or stems. Seal the bag with a wire twist. Keep your Violet in the bag for one week. After you have removed the Violet from the bag, it will be safe to resume your normal watering and fertilizer schedule.
Here's a helpful one-page guide to ROOTING VIOLETS BY LEAF as a PDF and PNG image.