Flower Forms of Peonies
Single
A ring of 5 or more petals with the center of peony made up of stamens with pollen-bearing anthers.
Japanese
A ring of petals around a central cluster of modified stamens that are narrow and flat and bear no pollen.
Anemone
A ring of petals around modified stamens which are fully transformed into narrow petals (petaloids)
Semi-Double
Several rings of petals around visible pollen-bearing stamens.
Double
Many concentric rings of petals with no visible stamens (stamens have been completely transformed into petals).