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Monday - October 13, 2008

From: Clarendon Hills, IL
Region: Midwest
Topic: Diseases and Disorders, Herbs/Forbs
Title: Mildew in Phlox paniculata
Answered by: Barbara Medford

QUESTION:

I planted garden phlox (phlox paniculata) in my front landscaping and it is suffering from mildew. It is wet on that side due to a down spout and it may benefit from being split. Does anyone know of a treatment to eliminate the mold? They really do not flower well.

ANSWER:

Your native Phlox paniculata (fall phlox) is probably not in any danger from the mildew, although it does make the plants somewhat unattractive. Mildew is common in the Fall, because of cool nights and still-warm days. Too much water in a flower bed, such as from a downspout, can cause other problems in plants, like root rot. You might want to consider finding a way to channel the outflow from your downspout away from the flower bed. Since your phlox is a perennial, you might also consider dividing it and moving it to another area. The best preventions of mildew are good air circulation and sunshine. Since it isn't always possible to provide those, read this article from About.com Organic Gardening on Preventing and Controlling Powdery Mildew. One tip we picked up from this and other sources, which surprised us, is that one of the best treatments for powdery mildew is a good spray of water on the affected plants. It should be done early in the day, so that the water will have plenty of time to dry before sundown, but it does seem to work. You could go on to try the baking soda spray solution mentioned in the article, although we have heard mixed reports on the efficacy of that method. There are fungicides available, but that is likely overkill for this problem. Rake up the fallen leaves and blooms, and keep the area clean, so mildew can't winter over.