Hi joannakat,
a 10-10-10 might be a little too strong for peonies. The recommendation is typically to fertilize with a tulip/daffodil bulb fertilizer in the Fall. It is best to fertilize first so you can see where the eyes/roots are, then cut down the stems. You would want to apply the granular fertilizer around the stems.
I use Espoma Organic Bulbtone which is a 3-5-3 NPK nutrient.
Welcome and hope this is helpful.
