Root and crown rot of violets, and most other plants, can occur if their roots are kept too wet. Disease fungi may or may not be present for rot to occur. Leaves of plants with rotted roots and crowns usually turn yellow, mushy, and fall off. It's normal for old leaves to have this same sequence of events, but they will be more numerous on plants with a rot problem.
Because the first symptom of root and crown rot is droopy leaves, a natural reaction is to water the plant more because it seems to be wilted from lack of water. But watering can be a big mistake. When a plant's root system is constantly saturated with water, the roots can lose the ability to absorb water and oxygen. Under these wet conditions the roots and/or crowns tend to decay.
There are several ways to avoid creating rot conditions. Be sure the potting mix isn't too heavy. Also, the mix should be free from disease organisms. Perlite added to the mix can help prevent oversaturation. Water the plant when the soil feels dry to the touch, but be careful not to allow the soil to dry out completely. The pot should have good drainage and shouldn't sit in water. Prevention is the easiest and most successful "cure."
This article originally appeared in the February 7, 2003 issue, p. 7.