Whenever the leaves begin looking peaked, cut them back. They should do fine next year, provided you did give them some water earlier this season. My peonies have seen better days. They look so bad, they are taking away from the blooming flowers near them. If I have to live with the ugly foliage I will, otherwise I would like to prune them back.
Peonies begin growing so early in the spring, that they often begin to decline in late summer.
By all means prune off the dead or damaged foliage and clean up your garden. They should have set flower buds for next season by now. As long as you watered this summer, you should still have a show next spring. Back To Top I planted several peony bushes last summer. One had about 15 buds on it but only two opened.