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Flower forms: The anatomy of peonies

by Timber Press on January 4, 2018

in Design, Gardening

‘Nosegay’, single

Peonies are stunningly beautiful, easy to grow, relatively carefree, and adaptable to any garden style. They are a favorite flower everywhere they can be grown and for good reason: the heady fragrances and enchanting colors of a peony-rich garden can evoke memories, capture an enchanted moment, and represent hope, friendship, romance, or gracious hospitality. To discuss the great diversity of peony flowers, we have to discuss the different floral forms.

Peony floral forms established by the American Peony Society are based on the overall structure of the flower and how the floral parts relate to each other. The system works well for all herbaceous peonies. The top or terminal flower on a stem is the one that is evaluated since the side flowers can occasionally be slightly different. The basic types are single, Japanese, anemone, bomb, semidouble, and double. The technical differences are based on the number of rows of petals, the condition of the guard petals (the outer row of petals), the presence of stamens and anthers (the parts that bear pollen), the partial to complete transformation of anthers to petals (at least as recognized by the typical gardener), and the reduction of the carpels (the potential seed-pods) to insignificance. The forms grade into each other, much like colors of the rainbow. However, the terms are essential to describe and understand the look of the flowers. These terms are everywhere in nursery catalogs and peony shows. An excellent, detailed, and illustrated series of articles on these forms is available online from the American Peony Society. The three-part series is called “Peony Flower Anatomy.” A more complex set of floral forms is used in Asia, especially for tree peonies, and is sometimes encountered in specialty catalogs.

‘President Lincoln’, single

Single peonies have one or two rows of large petals, a multitude of golden pollen-bearing anthers, and one to five carpels, where seed is formed. Single peonies look a bit like wild roses, only much bigger (and better). ‘Krinkled White’, ‘Roselette’, ‘Scarlet Heaven’ and ‘Sea Shell’ are all examples of single peonies.

Japanese and anemone peonies are similar to single peonies with one or two rows of petals, but their stamens and anthers have been transformed into narrow, petal-like structures. Japanese forms may show a trace of pollen but are usually not pollen-bearing. Anemone forms have anthers that become wider petal structures and no longer contain pollen. The two forms intergrade, but are separated as follows.

‘Do Tell’, Japanese

Japanese Blooms
The stamens of Japanese blooms are transformed into narrow, petal-like structures (staminodes). These staminodes retain shape, texture, and usually color features that belie their original origin as stamens. The flowers of some Japanese forms have a yellow center that looks like an egg yolk. ‘Garden Lace’, ‘Mahogany’, and ‘Walter Mains’ are among the well-known examples.

‘Gay Paree’, anemone

Anemone Blooms
The stamens of anemone blooms are transformed into broader petal-like structures (petaloids.) These petaloids show no indication in shape or texture of being derived from stamens, although their color can be yellow to nearly matching the true petals. Some anemone forms have the overall effect of a sea urchin at the center of the flower. ‘Belleville’, ‘Bouquet Perfect’, and ‘Gay Paree’ are examples of anemone forms.

‘Red Charm’, bomb

Bomb peonies are named for the mounded French ice-cream dessert served on a plate (bombe), and they are a feast for the eyes. Bomb forms represent the ultimate in the transformation of stamens to petal-like tissue, here called inner petals. The inner petals are convincingly petal-like, but form a beautifully dense petal-ball (the ice cream mound) that sits on the plate of guard (outer) petals. The guard petals can be the same or a different color than the inner petals. Among the many popular bomb-type peonies are ‘Angel Cheeks’, ‘Big Ben’, ‘Bridal Shower’, ‘Monsieur Jules Elie’, and ‘Red Charm’.

‘Cora Louise’, semidouble

Semidouble peonies have many rows of petals, with some stamens and anthers present among the many petals. What happened to the other stamens and anthers? They have been transformed into the extra petals. The carpels may be normal or reduced in size and number. Among the best known semidoubles are ‘Buckeye Belle’, ‘Coral Sunset’, and ‘Garden Treasure’.

‘Pink Pearl’, double

In double peonies, all the stamens and anthers are transformed into large petals that are nearly identical in size. In some cases, the carpels are completely transformed, too. Beginners sometimes confuse double peonies with bombs: bombs are easily recognized by the plate of guard petals, whereas in all the doubles the petals are delightfully similar. This is a very large group of peonies, and even a short roll-call begins with ‘Bowl of Cream’, ‘Chestine Gowdy’, ‘Duchesse de Nemours’, ‘Kansas’, and ‘Mrs. Franklin D. Roosevelt’ followed by many, many more.

David C. Michener is an associate curator at the University of Michigan, including the Peony Garden at the Nichols Arboretum, where he oversees the rejuvenation of the largest public collection of historic herbaceous peonies in North America.





Carol A. Adelman is the founder of Peony Paradise–Adelman Peony Gardens near Salem, Oregon. She and her husband grow 484 varieties of peonies. Carol is on the board of directors for the American Peony Society, is the president of the Pacific North West Peony Society, and is the charter organizer of the Salem Hardy Plant Society.




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