My mint plant leaves are turning brown and drying up and the stems are getting brown scaly bumps all over them. A friend gave me a mint plant about 4 months ago. She was growing it outside. We live where it snows in winter, so I want it to grow it inside. I planted it in new potting soil, in a self watering pot. I keep the soil moist to the touch. At first I noticed holes in some of the leaves so I thought there was sone sort of "bug" there. There isn't anything on the underside of the leaves, no webbing, like from spider mites. The leaves are drying and curling up and now there are brown scaly bumps forming on the stems. Any ideas how to stop this?
I suggest you put it in an ordinary pot with a drainage hole, and water when the surface of the compost feels just dry to the touch, water thoroughly, then pour away any excess water in an outer pot or tray after 30 minutes. The potting compost should be allowed to dry out a bit between waterings - keeping it moist all the time is not a good idea, and in my experience, self watering pots tend to keep the roots of the plant within too moist. Mint likes well drained soil conditions - if kept too damp all the time, root rot is likely. Cut off blackened stems and leaves when repotting.
The scaly bumps appear to be dry adventitious roots - these sometimes form as a stress response to less than perfect growing conditions.