I have had success with my peonies in supporting them as they bloom by using tomato cages. Attached are photos showing them upside down. I curl back the legs into pinwheels so they aren't hazardous, then guide the young plant into the lower part of the cage. You can secure the bottom rim with metal staples used for holding down drip irrigation of 1/2" diameter. Only the cheap thin tomato cages should be used so they blend into the greenery and are easy to bend. The legs of the thicker ones are harder to bend by hand and the cage is too visible.

Eileen