Persian violets, also known as German violets, are tender annual plants that produce blooms in hues of blue and purple continuously throughout the growing year. They have a dense low mounding growth habit and thrive in partial shade conditions. Persian violets are winter hardy in USDA zones 9a through 11, growing as an evergreen perennial ground cover in some temperate climes.
Cut back Persian violet foliage in the fall after the first hard frost. Use secateurs or hand shears to cut down to the crown of the plant just an inch or two above the soil line. For climates where Persian violet overwinters, examine the plant for any damaged, diseased or dying leaves and branches, and remove just those. Cleaning the plant of damaged or decaying foliage material will prevent the invitation of rot or disease over the winter months.
Water your Persian violet plants deeply in the fall. This will help the plants to survive winter drought stress by boosting both the soil and root moisture content. If there is insufficient rainfall during the winter to keep the soil evenly moist, augment rainfall with irrigation to sustain the plants.
Mulch over the sheared plant crowns or around the base of overwintering violets with at least a 3-inch blanket of organic material. Consider using shredded bark, wood shavings, compost or cocoa bean hulls for the best insulating effect. Cover the soil with the mulch from the crown at the base of the plant out at least several inches beyond the plant borders.