African violets are an all-time favorite blooming houseplant. Given the proper growing conditions, African violets will last for years. Insufficient light is one of the major reasons Violets do not bloom well. Violets must have 10 to 14 (16 is max) hours of bright light per day (no direct sun). Variegated varieties usually need more light than the plants with solid green leaves because there is less chlorophyll that is used to turn light into food for the plant. If you don't have these ideal lighting conditions, you can enhance the light for certain violets by sitting them on mirror tiles as large or larger than the violet. This reflects the available light back to the violet. Also, twin tube fluorescent lights are ideal. Place the tubes eight to ten inches above the foliage for mature standard plants, and six to eight inches for miniatures, leaves, and seedlings. Because violets process nutrients during the "resting phase", they should also have eight hours of darkness per day.
TEMPERATURE
70° - 75° Fahrenheit is usually ideal, although 60° - 85° Fahrenheit is tolerated for short periods of time.
HUMIDITY
40% - 50% relative humidity is usually ideal. The humidity near your plants can be raised by supporting the plants over water. Wick watering is ideal for this because the plant sits on top of a reservoir of water.
POTS
Use "clean" plastic or ceramic pots. Terracotta pots tend to collect salts, harmful chemicals, and pests. I advise against using them. Don't use a pot that is too large. Never move a plant to a larger pot until the roots fill the present pot. Violets tend to bloom most when they are slightly root bound.
FERTILIZER
Either lack of fertilizer or too infrequent feeding is one of the reasons for lack of blossoms. Most growers use a "soil-less" potting mix with little nutrient content; this requires using a dilute fertilizer solution each time the plant is watered.
Peters 12-36-14 is my recommendation. Mix 1/4 teaspoon per gallon of water and use this mixture each time you water. Use a liquid African violet fertilizer sprinkled over the top of the soil every 10 weeks. This will increase the amount of blooming.
WATER
Never use water that has been through a softener. Using distilled water all the time is not good either because it deprives the violet of trace minerals that would ordinarily be present in the water. Chlorine in the water might cause problems for the violet. Let the water stand overnight in an open container to let the chlorine evaporate out of the water. Bottled "spring water" is a good substitute if your tap water is not good. Use water that is room temperature (neither cold or warm.) Keep the violet "just moist", not wet. Never allow the plant to become completely dry. "Wick" watering is also a good technique. Place a nylon wick on the bottom of the pot with the loose end extending out of the pot about 4 inches. Hang the loose end of the wick in a container of fertilizer/water mixture (see above). Never let the pot touch the water - only the wick should touch the water. This wick will keep the violet watered for 2-4 weeks depending on the size of the reservoir.