Q: I planted forty impatiens plants in a bed this past spring. The flowers did very well for most of the summer. In early fall, the plants started to drop leaves and flowers, exposing the stalks. There is a gray powder on the leaf backs. Is this downy mildew? Can I plant pansies in this bed?
A: Your description exactly describes this fatal disease’s progression. Impatiens downy mildew continues to impact greenhouse growers and gardeners across the country. Once a bed is infected, you can’t plant impatiens there for several years. One theory is that the process of breeding impatiens to produce lots of flowers lowered the plant’s resistance to downy mildew. It is a very specific disease, so it won’t affect your pansies at all. Remember that New Guinea impatiens, coleus, or Sunpatiens could grow in that spot next year without problems.