Improve soil that is too acidic by adding ground limestone. At Cricket Hill Garden, we add limestone to the soil at least once per year. If you do not know your soil pH, it is a good idea to have it tested. Ideally peonies grow well in a pH of 6.5 to 7.0
At Cricket Hill Garden, we use about 1/2 cup at the drip line for tree or herbaceous peonies. Scratch this in and water. The pH of the soil will change slowly. If the pH is too high or too low for peonies, the plants cannot will not grow well. Calcitic lime is low in magnesium, unlike dolomitic lime. If there is too much magnesium, this natural element will prevent the uptake of nutrients. Calcitic limestone is preferred for this reason.