Prevent peony botrytis
Botrytis is a fungus that often attacks peonies as they sprout, causing leaves and buds to turn brown and stems to rot and fall over.
If you live where the soil is acid, one way to prevent botrytis is to keep the crown and soil around it covered with a 1-in.-thick layer of limestone. It neutralizes the acid and helps kill the botrytis, which waits in the soil and coats the peonies as they emerge. This alkaline element also helps release chemical nutrients that can be “locked up” in an acid soil, helping the plant get growing again after its winter dormancy. Be sure to use pea gravel-sized crushed limestone, calcium carbonate, not the powder that’s used on lawns.
In the fall, cut your peonies to the ground and remove debris where the fungus hides. Replenish the limestone if needed to keep an inch-thick layer over the plant’s crown. Then top with mulch for winter. Crushed limestone mulch kills botrytis in the soil and on the emerging plants.