Peony Leaves Curl
I'm not sure what would cause the peonies to turn black with rolled leaves. There is a fungus that attacks some peonies called Phytophthora blight, but this usually occurs in cool, moist conditions. You could take a sample of the foliage to your local extension service or garden center to see if they think it's a fungus. If so, you'll need to spray with a fungicide. But, i suspect, the problem is where you have them planted. Peonies like full sun, but rich, well drained soil. If you soil is hard clay, this could be causing the plants to struggle in a variety of ways. You might consider making a new bed with enriched soil and moving the plants this fall. Do not move them now. Also, do not plant them too deeply. Peonies like to be planted so their fleshy roots are just under the surface of the soil. And don't expect flowers the first year after blooming. On older varieties it may take a few years for them to reestablish. I'd also be sure to mulch them to maintain constant soil moisture.
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