Water Stains on Leaves
Question: I’m very careful with my watering, not to get any on the foliage of the plant, but many of my violets still show what seem to be stains on their leaves. These appear mostly on the leaf edges.
Answer: This is a very common problem, particularly when nights are cool and soil is damp. What’s happening is that cool nighttime temperatures are causing “dewdrops” to form on your plant’s leaves. When the “drop” evaporates, it leaves behind a stain. We find this particularly a problem in the spring and fall, when days are warm and nights are cool, and usually after we’ve watered and the soil is wetter than usual. The solution, of course, would be to moderate daytime and nighttime temperatures, and to water plants early in the day. This would let they dry some before temperatures drop at night. Doing these thins will also help control powdery mildew.