I grow almost all my violets from leaves. The most important thing to remember is to choose a healthy leaf. If your plant leaf is one with variegated foliage, be sure to select a healthy leaf with a lot of green. Using a sharp knife, cut the petiole on an angle. You can dip the cutting into a rooting powder before planting it. Place the cut petiole about 1/2 inch in length into a solo cup filled with either a starter mix of one part perlite and one part vermiculite, or your regular potting soil. I prefer my own potting mix with an inch of perlite in the bottom of the cup. Slightly moisten the soil, but don't make it too soggy, to seat the leaf in the soil. To create a greenhouse environment, place a baggie over the top of the leaf and put a rubber band at the top of the pot. Cut a small hole into the top of a baggie so the moisture doesn't build up and cause the leaf to die.

No. 1 - Potting

If you are growing where it is hot and humid most of time you need to keep your soil very light. This is most important, a good soil mix supplies the plant with the necessary moisture and nutrients. If not grown in the right soil the other factors will be of little use. The soil should be loose to enable the root development and air and water passages. African Violet Soil should be slightly acid, and the PH about 6.5. I store it in an airtight container (5 Gallon bucket) to ensure against disease, organisms and soil insects. This is the soil mix that I use:

4 quarts of Peat (BX)
1/2 cup of Charcoal
3 to 4 quarts of Perlite
1 Tablespoon Dolomite Lime
2 quarts of Vermiculite
1 Tablespoon Dehydrated Cow Manure
1 quarts of Baccto (pasteurize)
3 or 4 cups of water to mix

African Violets grow and bloom better in small pots. Small plantlets should be planted into 2" pots or solo cups. They should remain in this pot until blooms begin to appear. This is an indication that it has a good root system. At that time they can be repotted into a 3" pot, about 3 or 4 months. The plant should be left in that pot until it is about 9 inches in diameter. Then repot into a 4 " pot. If the plant does not develop this much, then it should be returned to the same size pot. When the plant is about 13 to 14 inch across, it can be transplanted into a 5" pot.

No. 2 - Watering and Fertilizer

Without proper watering your plant will be stressed, which will cause serious damage to the roots and make your plants highly vulnerable to crown rot fungi. Wick or mat method of absorbing the moisture from the bottom is a great way to keep the plant evenly moist. Plastic peanut butter jars for the three-inch pot and jelly jars for my miniatures and semis are great. All drinking water should be suitable for watering plants.
You need a balanced fertilizer with all the necessary elements and the right PH in order for the plant to be able to take up fertilizer to give the plant proper nutrients. I constant feed, by using no more then 1/4 teaspoon of fertilizer per gallon of water. Too much fertilizer will leave marred burn around the leaf edges. It is a good idea to leach your plants every 6 to 8 weeks to reduce the possibility of harmful salt build-up, which can cause damage to the roots. Leaching is the process of running clear, lukewarm water through your plant. If you repot often, leaching is not always necessary. I like letting my plants dry out slightly sometimes between watering. If a plant for some reason becomes dry and wilted, water with small amounts of clear water until it becomes turgid again. Afterwards, the fertilizer may be applied. If a plant doesn't seem to be growing on a reservoir, I will let it dry out slightly and hand water a couple of times before putting it back on constant feed.

No. 3 - Lighting, Temperature and Humidity

In the South, window growing can be done. In the heat of summer you may have to move plants to a different location away from a lot of direct light. Without good light African violets will not bloom. Many violet growers prefer to control the light by using fluorescent lights. (One warm and one cool bulb) I prefer the Sylvania Gro-Lux, one standard and one wide spectrum. I like to replace one bulb every 6 months when growing for show. The older bulbs are reused on my babies and smaller plants for another 12 month. All my shelves are 18 inches from the light, and they are on timers for 13 hours a day at all times. Some plants prefer less light and should be grown at the ends of the bulbs. Variegated foliage seems to need more and can placed in the center. I prefer to grow the variegated plants on the bottom shelf because of the temperature. When you change your bulbs it is also a good time to replace your sticky traps. They do catch lots of unwanted flying bugs.
Heat in the summertime is hard on the violets and they will not survive without air conditioning. I find that they do not like it over 80 degrees. This is under the fluorescent lights when in use. Plants should be kept at an even temperature at all times. In the South the temperature fluctuates, which increases the chances of fungal diseases. I find, that two plants stands in a room (8 lights) is the maximum for heat. You can alternate your timers so they are not all on at the same time. Plants need good air circulation, which is very important. A (ceiling) fan is a must. Stale stagnant air will cause mildew to form on the leaves and blossoms of the plant. Plants should not touch each other, so be sure to allow adequate space between violets and provide good air circulation around them to prevent mildew. Be sure to rotate your plants so they don't become lopsided. Ideal humidity is from 50% to 60 %. Maintaining this level of humidity will encourage longer lasting and larger blooms. If it goes over 70%, fungus is likely to become a major problem. Plants need to transpire (breathe off) moisture into the air, which brings water (fertilizer) up through the roots. A dehumidifier can be very helpful to keep a balance between AC and heat.

No. 4 - Pests

I hate to say this, but bugs love hot and humid weather. We don't have a good freeze to control these undesirables. There are a few insects that will attack African Violets. Soil mealy bugs, fungus gnats, and springtails can be controlled with Granular Systemic Marathon by sprinkling granules over a layer of potting soil in the bottom of the pot. (Lasts about 10 to 12 weeks) For mites and thrips I spray a fine mist of Chipco and Avid to the plant leaves.( 1/8 teaspoon of each, together with two drops of dishwater soap to two 2 cups of water) Repeat once a week for three weeks if you have a problem with these pests.

No. 5 - Disease

Humid weather also brings even bigger problems, mildew and fungal disease. You will see a white film on the leaves or on the blooms when these are present. Most fungal disease is airborne. When treating mildew I use Lysol for small jobs. Keep the spray well above the plant and let it fall as a fine mist on the plant. Spraying Captan in the spring and fall has also worked very well for me. I use 1/8 of a teaspoon to 2 cups of water and two drop of dishwater soap. There are many chemical spays on the market today. Take precautions and follow the instructions on the product you are using. Rubber gloves and a mask should be worn. Wash hands and all exposed skin with soap and water immediately after using any chemical. I choose to spray just for precaution against insects and disease here in the South about every 4 to 6 weeks.

Observation!  
A good grower will notice any changes in their violets. You need to catch disease or pests in early stages. These unwelcome guests are much easier to get rid of before they begin to multiply. You need to take all precautions when bringing a new plant into your home. The "Green Thumb" comes from a combination of enjoyment with plants and acquiring knowledge on how to care for them.

Until next time ..... Happy Growing