Leaf spot diseases on Peony are very common in our area. In the old days people used to try and treat with fungicidal sprays. Fungicides are simply preventative, not curative and need to be repeated throughout the season so we don't recommend them much anymore.

These blotches usually begin after the beautiful bloom time and don't tend to seriously impact the plant. While they can be pruned out if it affects and browns the whole leaf, if there is still green tissue we suggest letting it be as that green tissue is still supporting energy storage into the roots for the following season. Once they are browned or dieback for the season, then you can prune them out and dispose of them in the trash.

Christine

Thanks for the info.  The plants do seem OK, just not very attractive once
the brown spots kick in.

On Thu, Jan 28, 2021 at 12:13 PM Ask Extension <askextension>
wrote:

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If your peonies are robust and can afford to lose a little leaf surface, you can prune off the worst of the leaf blotch during the season.

Peony leaf blotch is best managed through sanitation anyway. The fungus will have survived the winter in infected plant debris. Diseased plant material should be removed in fall or early spring (before new shoots emerge). Cut off the stems at ground level. Remove the plant debris from the area and destroy it. 

Proper spacing and watering can help to minimize the severity of the disease. Space peonies 3 to 4 feet apart. When watering is necessary, avoid wetting the peony foliage. This may cut down on the amount of infection. 

Ellen