The right time to harvest a peony is in the marshmallow stage. If harvested in this stage, you will get six to seven days in the vase, and up to ten in ideal conditions.
In the marshmallow stage, the bud is softening and swelling, and beginning to produce visible color. When you pinch the bud, it feels soft, just like a marshmallow.
Immature peony buds are said to be in the marble stage. These buds are hard and round, and feel just like a marble. Immature buds likely will not open if harvested.
The fully open blooming flowers are past the stage for cutting. These flowers should be left on the plant to enjoy in the garden, as they will not last long in the vase.
Strip the bottom leaves from the stem, leaving only several leaves at the top.You can remove most of the side buds as well, or keep them for decorative purposes.
Freshly cut peony stems can be stored in a fridge.The cool temperatures will preserve them in the bud stage, until they are ready to be taken out and displayed.
Peony buds can be stored dry packed, and wrapped in paper or plastic, stored out of water. Dry stored peonies can be stored in a horizontal position in the cooler.
Peony buds can also be wet stored in a container in the cooler. Unlike those in dry storage, the buds in wet storage will slowly start to develop and open, even in the cold.
When the peony buds are removed from cold storage in the marshmallow stage they will open. Give them a fresh cut on an angle, place them in water, and they will bloom.