Most are herbaceous perennial plants 0.5–1.5 metres tall, but some resemble trees up to 1.5–3 metres tall. They have compound, deeply lobed leaves, and large, often fragrant flowers, ranging from red to white or yellow, in late spring and early summer.
The peony is named after Paeon (also spelled Paean), a student of Asclepius, the Greek god of medicine and healing. Asclepius became jealous of his pupil; Zeus saved Paeon from the wrath of Asclepius by turning him into the peony flower.
The family name "Paeoniaceae" was first used by Friedrich K.L. Rudolphi in 1830, following a suggestion by Friedrich Gottlieb Bartling that same year. The family had been given other names a few years earlier. The composition of the family has varied, but it has always consisted of Paeonia and one or more genera that are now placed in Ranunculales. It has been widely believed that Paeonia is closest to Glaucidium, and this idea has been followed in some recent works. Molecular phylogenetic studies, however, have demonstrated conclusively that Glaucidium belongs in Ranunculaceae, but that Paeonia belongs in the unrelated order Saxifragales.
Peonies can be classified by both plant growth habit and by flower type. Plant types are Herbaceous (Bush), Tree and Intersectional (Itoh), while flower types are Single (e.g., Athena, Dad, Krinkled White, Scarlet O’Hara, Sea Shell), Japanese (Nippon Beauty, Madame Butterfly), Anemone, Semi-Double (Paula Fay, Coral Charm, Miss America, Buckeye Belle), Double (Ann Cousins, Gardenia, Kansas, Paul M. Wild, Tourangelle) and Bomb-Double (Red Charm, Raspberry Sundae, Mons Jules Elie). Each category becoming more complex in the arrangement of petals. Herbaceous peonies die back in winter, regrowing in spring, while tree peonies lose their leaves in winter, but leave woody stems.
Intersectional peonies are crosses between tree and herbaceous types. They have the leaf form of the tree peony, but die back, have a bush form, but are shorter than herbaceous peonies. 
Chemistry and Biological ActivitiesEdit
Over 262 compounds have been obtained so far from the plants of Paeoniaceae. These include monoterpenoid glucosides, flavonoids, tannins, stilbenes, triterpenoids and steroids, paeonols, and phenols. Biological Activities include Antioxidant, Antitumor, Antipathogenic, Immune-System-Modulation Activities,Cardiovascular-System-Protective Activities and Central-Nervous-System Activities.
This varies according to type, For instance Tree peonies are propagated by grafting but Herbaceous and Itoh peonies by root division. However new peonies are raised from seed. 
- Herbaceous species (about 30 species)
- Paeonia abchasica
- Paeonia anomala
- Paeonia bakeri
- Paeonia broteri
- Paeonia brownii (Brown's Peony)
- Paeonia californica (California Peony)
- Paeonia cambessedesii
- Paeonia caucasica
- Paeonia clusii
- Paeonia coriacea
- Paeonia daurica
- Paeonia emodi
- Paeonia hirsuta
- Paeonia intermedia
- Paeonia japonica (Japanese Peony)
- Paeonia kesrouanensis (Syrian Peony)
- Paeonia lactiflora (Chinese Peony, known as 芍藥 "sháoyao" (literally: "most beautiful" ) in Chinese, "common garden peony")
- Paeonia macrophylla
- Paeonia mairei
- Paeonia mascula (Balkan Peony)
- Paeonia mlokosewitschii (Golden Peony)
- Paeonia obovata
- Paeonia officinalis (European Peony)
- Paeonia parnassica (Greek Peony)
- Paeonia peregrina
- Paeonia rhodia
- Paeonia sinjiangensis
- Paeonia sterniana
- Paeonia steveniana
- Paeonia suffruticosa (Rimpo Peony)-
- Paeonia tenuifolia
- Paeonia tomentosa
- Paeonia veitchii (Veitch's Peony)
- Paeonia wittmanniana
- Woody species (about 8 species)
- Paeonia decomposita
- Paeonia delavayi (Delavay's Tree Peony)
- Paeonia jishanensis (syn. Paeonia spontanea; Jishan Peony)
- Paeonia ludlowii (Ludlow's Tree Peony)
- Paeonia ostii (Osti's Peony)
- Paeonia qiui (Qiu's Peony)
- Paeonia rockii (syn. Paeonia suffruticosa subsp. rockii; Rock's Peony or Tree Peony)
- Paeonia suffruticosa (Chinese tree peony, known as 牡丹 "mǔdān" in Chinese)
- ↑ 1.0 1.1 1.2 Josef J. Halda and James W. Waddick. 2004. The genus Paeonia. Timber Press: Oregon, USA.
- ↑ 2.0 2.1 Michio Tamura. 2007. "Paeoniaceae". pages 265-269. In: Klaus Kubitski (editor). The Families and Genera of Vascular Plants volume IX. Springer-Verlag: Berlin;Heidelberg, Germany.
- ↑ Flowers in Greek Mythology, VALENTINE floral creations. Accessed 23 June 2008.
- ↑ James L. Reveal. 2008 onward. "A Checklist of Family and Suprafamilial Names for Extant Vascular Plants." At: Home page of James L. Reveal and C. Rose Broome. (see External links below).
- ↑ David J. Mabberley. 2008. Mabberley's Plant-Book.Cambridge University Press: UK.
- ↑ Wei Wang, An-Ming Lu, Yi Ren, Mary E. Endress, and Zhi-Duan Chen. 2009. "Phylogeny and Classification of Ranunculales: Evidence from four molecular loci and morphological data". Perspectives in Plant Ecology, Evolution and Systematics 11(2):81-110.
- ↑ Shuguang Jian, Pamela S. Soltis, Matthew A. Gitzendanner, Michael J. Moore, Ruiqi Li, Tory A. Hendry, Yin-Long Qiu, Amit Dhingra, Charles D. Bell, and Douglas E. Soltis. 2008. "Resolving an Ancient, Rapid Radiation in Saxifragales". Systematic Biology 57(1):38-57. (see External links below).
- ↑ Heartland Peony Society
- ↑ He, C.-N., Peng, Y., Zhang, Y.-C., Xu, L.-J., Gu, J. and Xiao, P.-G. (2010), Phytochemical and Biological Studies of Paeoniaceae. Chemistry & Biodiversity, 7: 805–838. doi: 10.1002/cbdv.200800341
- ↑ How to Propagate Peonies
- ↑ http://livinginseason.blogspot.com/2006/06/peony-most-beautiful.html
- Family and Suprafamilial Names At: James L. Reveal
- Shuguang Jian et alii on phylogeny of Saxifragales Template:Doi
- Paeoniaceae in Topwalks
- Germplasm Resources Information Network: Paeonia
- Flora Europaea: Paeonia
- Ornamental Plants from Russia: Paeonia
- The Peony Society (UK)
- Canadian Peony Society
- U.S. Peony Society
- Carsten Burkhardt's Open Source Peony Project
- German Peony Group
- China Daily article on the 2003 national flower selection process
- Rockii Tree Peony
- Paeonia mascula in the National Park of Alta Murgia, Apulia - Southern Italy