German violet, more commonly called Persian violet, is in the gentian family and not a true violet. Popular as gift plants, they have shiny, heart-shaped leaves and small purple flowers with yellow centers. German violets generally are kept indoors or in greenhouses because they are tropical and don't tolerate temperatures below 55. In very warm regions, German violets can live outside in shade, but they must be brought indoors during the cooler months.
Acclimate German violet to the indoors. Bringing the plant inside just when the weather turns cold could cause stress or shock from the sudden change in temperature.
Put your plants in full shade about three weeks before you plan to bring them indoors. Although German violets prefer very little sunlight, there is even less light indoors, so the plants need to get used to darker, cooler environments. Put the plants outdoors in an area that receives no direct daytime sun once or twice a week for two weeks, and two or three times a week for the third week.
Reduce the plant's water, starting three weeks before you plan to bring it inside. Give it as little water as possible, but don't let it wilt.
Stop giving German violets fertilizer after their last summer flowering. Plants need to have a period of rest in the winter, and fertilizer encourages growth.
Put German violets indoors where they get a lot of sun. German violets need more sunlight when they're indoors, so a window with Southern or Western exposure probably would be best. Make sure the plant is at least six inches from cold or icy windows.
Keep the German violet's soil fairly dry over the winter, and make sure it has good drainage. Plan to water the plant once every week or 10 days, depending on the humidity in your region.