Pls help my Peonies as if powdery mildew

Asked July 1, 2017, 7:29 AM EDT

Hi, pls let me know what happens to my Peonies. I planted them 3 yrs ago. Since then, they give gorgeous huge flowers and lush greenery leaves. Then suddenly after they bloomed luxuriantly this Spring, all the leaves and stems have those white or grayish powder as if powdery mildew. Pls let me know how to save them. Thanks in advance.

Montgomery County Maryland powdery mildew peony shrub

1 Response

Powdery mildew has become a bigger problem on peonies the past few years. Make sure there is adequate sunlight and good air circulation to reduce humidity levels. Allow proper plant spacing for the same reasons. Pruning for better air circulation also may help. Practice good sanitation.

Cut down all infected foliage this fall as soon as frost turns it brown (or before if the mildew has killed it.) Get rid of this infectious material. Next spring, monitor your peonies, and as soon as you see one infected leaf, pull it off. You will have to decide it you want to spray a fungicide or a horticultural oil labeled for powdery mildew or tolerate it. Fungicides are preventative--not curative. They will halt further infection, but cannot restore infected leaves to health. There are no resistant peony varieties.
Here is our website info on powdery mildew: http://extension.umd.edu/hgic/powdery-mildew-annuals-bulbs-groundcover-perennials-and-vines
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