Common Problems
The African violet is one of the easiest plants you can grow. Although it isn't problem free, the two most common questions in growing African violets are "Why do African violets turn color?" and "How do I get rid of mealy bugs on my African violet?"
Why Do African Violets Turn Color?
Although several conditions may cause your African violet to change color, the two most common reasons are that your plant is too cold or too wet.
Because they're too cold
Although African violets prefer temperatures on the warm side (75F to 80F during the day), usually they acclimate well to normal home temperatures. However, even though your thermostat is set at 72F day and night, a plant located on a windowsill may still get a nighttime cold, which causes it to darken and eventually wither.
Some experts suggest that you remove your African violet to a warmer spot during the night, but remember that the Saintpaulis declines if you move it too often. The safest method to prevent night chilling is simply to draw the window shade at night. If your window is without a shade, provide protection by placing a newspaper or piece of corrugated cardboard between your African violet and the window.
Because they're wet
In the wild, African violets grow in mountain rock crevices in catch-as-catch can soil composed of matter that literally falls through the cracks. This makes for a very sparse and porous growing medium, a preference that your domestic Saintpaulis inherits from its wild ancestors.
Water you African violets only when the soil feels dry to your touch. At the end of watering time, be sure to empty any standing water in a tray or saucer. When watering your African violet from the top, be sure to keep water off the foliage since it causes discoloration in white or yellow rings, lines, or blotches. Over watering also makes African violets susceptible to leaf mold, which in turn makes the foliage appear to darken or turn color.