Peony Floral Forms
Due to millennia of human selection, peonies today come in a broad range of colors, forms, and fragrances. Wild peonies also come in a variety of colors, but are generally simpler-looking and are considered to have a “single” floral form. The key features are outlined below. The forms intergrade, but technically every flower has to be placed in a form. The forms recognized by Chinese and Japanese connoisseurs vary from the forms given here, especially once tree peonies are included.
More Information
The American Peony Society recognizes six different floral forms.

Single
Similar to the wild form of the peony with five or more guard petals arranged around the carpels and pollen-bearing stamens of the flower. This is the fundamental peony flower form.

Japanese

Anemone

Bomb

Semi-double
Five or more outer guard petals with a center of smaller inner petals often decreasing in size as they near the center of the flower. Pollen-bearing stamens may be intermixed with petals or be present in the center of the flower. Occasional transfomation of stamens to petal-like structures.

Double
Five or more outer guard petals with a center of stamens and carpels that have been more or less transformed into petals – creating the full body of the flower. Occasional stamens may be interspersed throughout the flower.

Tree
The tree peony is native to China. As suggested by its name, the tree peony’s stems are woody. Unlike the herbaceous peonies, the tree peony’s woody stems remain in the fall after the leaves have died and fallen off. Tree peonies bloom somewhat before herbaceous peonies, putting on a show two to three weeks prior to the main herbaceous peony beds. Tree peonies come in single and double forms and in colors usually not seen in herbaceous peonies such as purple and yellow.
Pictured: lavender tree peony is ‘Guardian of the Monastery’