Persian Violets, Execums, also known as German Violets -should be grown in full sun, bright light during the winter months, during the summer place them in semi shade for more vibrant color blooms. During Winter and the cooler periods of Spring and Fall, Exacum grow best at 60 to 65 degrees F. at night, and 72 to 77 degrees F. in the daytime. But in the summer, they respond with much faster growth because of warmer temperatures and longer days. Exacum is a moderate feeder. They grow best by alternate use of a 15-16-17 peat-lite special and calcium nitrate every third watering. Lower strength in Winter, higher strength in Summer. During the winter months since lighting is shorter in length, let soil dry between watering and cut the fertilizer in half the amount and strength.