(2001)  
 
KEY TO SPECIES
1. Flowers solitary, erect; disc leathery, sheathing the carpels to at least half their length (Section Moutan DC.): 2
2. Carpels 2-5, glabrous, sheathed to no more than two-thirds their length by the disc; leaves much divided into (29-)33-63 leaflets:.....5. P. decomposita

5. Paeonia decomposita Hand.-Mazz., Acta Hort. Gothob. 13: 39 (1939);.... Typus: China, NW Sichuan, Chosodjo, H. Siniffi 4641 (holotype, UPS- n.v., photo. K). ...P. szechuanica Fang, Acta Phytotax. Sin. 7 (4): 315 (1958);... Shrub up to 1.5 m tall. Leaves much divided into usually about 33-63 leaflets. Flowers large (12-15 cm diam.), single, rosepink, with the white disc enveloping the carpels only to about half to two-thirds of their length.

KEY TO SUBSPECIES
Carpels usually 5, occasionally 4-6; leaflets narrow, lanceolate to ovate-lanceolate:

5a. P. decomposita subsp. decomposita ....Leaflets narrow, lanceolate to ovatelanceolate. Carpels usually 5, occasionally 4 or 6. ...Found only in north-west Sichuan, in the valleys of the upper Dadu River (Da Jin Chuan, Chuosijia River) and its tributaries. The holotype and most other specimens come from localities within Barkam and Jinchuan Counties (Xian), but there is a specimen from Danba County and also one from northern Kangding County.

Carpels 2-5, often 3 or 4; leaflets broad, ovate to suborbicular:

5b. P. decomposita subsp. rotundiloba D. Y. Hong, Kew Bull. 52 (4): 961, fig. IA (1997). Typus: China, NW Sichuan, Lixian... Leaflets broad, ovate to suborbicular. Carpels 2-5, often 3 or 4..... Also restricted to north-west Sichuan, but in the valleys of the upper Min River and its tributaries, separated from subsp. decomposita by mountains some 4000 m high. Most specimens come from Maoxian County, with a few from near Lixian and Wenchuan, a couple from eastern Heishui County and one from near Zhenjiangguan in southern Songpan County.

(2001)  
 
Many gardeners and some botanists may find it surprising that all taxa formerly recognised in Subsection Delavayanae have been reduced to synonymy with P. delavayi Franch., except for P. lutea Delavay var. ludlowii Stern & Taylor, which has been raised to specific rank. Good reasons have, however, been put forward for these changes. D. Y. Hong, Pan and Yu (1998) analyse several populations of P. delavayi sensu lato and show that it is impossible to discern clear distinctions between them. D. Y. Hong (1997) makes a convincing case for raising P. ludlowii to the rank of species. These conclusions are supported by RAPI analysis, as reported by Y R Zou, Cai and Wang (1999).

(2001)  
 
KEY TO SPECIES
1. Flowers usually 2 or 3, more or less pendent; disc fleshy, surrounding only the base of the carpels (Section Delavayanae (F. C. Stern) J. J. Halda): 6
6. Carpels usually 2-5, sometimes more; petals, filaments and stigma often not entirely yellow; plants usually less than 2 m tall: .....6. P. delavayi

6. Paeonia delavayi Franch. in Bull. Bot. Soc. Fr. 33: 382 (1886); Huth, Bot. Jahrb. 14: 273 (1892);.....Shrub or subshrub,....glabrous throughout. Roots often fusiformly thickened, widely suckering. Lowermost 2-3 leaves biternate, the leaflets divided into 3-11 primary segments, these in turn each more or less deeply cleft into 2-11 lobes; segments and lobes linear to narrowly lanceolate, entire or occasionally dentate. Flowers 1 or 2-3 (3) on each shoot, 4- 10 cm diam.; petals yellow, yellow with a red or purplish basal blotch, red or purplish-red, or sometimes white, orange, greenish-yellow, or yellow with a red margin. Disc green, yellowish, yellow, red to dark red. Carpels 2-4(-8). W China (west & south-west Sichuan, W Yunnan, SE Tibet).
Many gardeners, and perhaps some botanists, will find it hard to accept that the several formerly recognised species and varieties listed as synonyms above should now all be included in the single species P. delavayi, with no infraspecific taxa. There are, however, good reasons for this, which have been carefully researched and explained by D. Y. Hong, Pan and Yu (1998). They have shown that characters that have previously been used to separate taxa now all included within this species, such as flower colour, presence or absence of a conspicuous involucre and width of leaf segments, are all very variable and show little or no correlation with each other and with geographic distribution.

(2001)  
 
Many gardeners and some botanists may find it surprising that all taxa formerly recognised in Subsection Delavayanae have been reduced to synonymy with P. delavayi Franch., except for P. lutea Delavay var. ludlowii Stern & Taylor, which has been raised to specific rank. Good reasons have, however, been put forward for these changes. D. Y. Hong, Pan and Yu (1998) analyse several populations of P. delavayi sensu lato and show that it is impossible to discern clear distinctions between them. D. Y. Hong (1997) makes a convincing case for raising P. ludlowii to the rank of species. These conclusions are supported by RAPI analysis, as reported by Y R Zou, Cai and Wang (1999).

(2001)  
 
KEY TO SPECIES
1. Flowers usually 2 or 3, more or less pendent; disc fleshy, surrounding only the base of the carpels (Section Delavayanae (F. C. Stern) J. J. Halda): 6
6. Carpels usually single, occasionally 2(-3); petals, filaments and stigma always yellow; plants 13-3.5 m tall: ....7. P. ludlowii

7. Paeonia ludlowii (Stern & Taylor) D. Y. Hong, Novon 7 (2): 157, fig. 1 & 2 (1997). Typus: China, SE Tibet, Kongbo Prov.. Miling (Mainling), Tsangpo Valley, 28 v 1938, Ludlow, Sherry & Taylor 4540....Shrub to 3.5 m. Roots not fusiform, suckering close to the stem bases. Lowermost 2-3 leaves more or less biternate; leaflets usually cleft almost to the base into 3 segments, each segment 3-lobed more or less to the middle, the lobes in turn entire or with 1 or 2 teeth; segments and lobes acuminate at the apex. Flowers usually 3 or 4 on each shoot. 10-12 cm diam.. nodding or somewhat pendulous; petals always entirely yellow. Disc yellow. Carpels 1 or occasionally 2(-3)... Endemic to south-east Tibet (Nyingchi, Mainling and Lhunze counties). It seems entirely appropriate for P. ludlowii to be regarded as a distinct species. The fact that the flowers, although usually larger than those of P. delavayi, have only one carpel, or sometimes two, is a very significant difference. The congested growth habit of P. ludlowii and its geographic separation from P. delavayi also support its elevation to specific rank.

(2001)  
 
KEY TO SPECIES
1. Flowers solitary, erect; disc leathery, sheathing the carpels to at least half their length (Section Moutan DC.): 2
2. Carpels 5(-7), tomentose, more or less entirely sheathed by the disc; leaves biternate or 2-3-pinnate, leaflets 9-33: 3
3. Shrubs often at least 1.5 m tall; leaves more or less 2 - 3-pinnate, leaflets 11-33, ovate to lanceolate; flowers comparatively large, more than 10 cm in diameter: 5
5. Leaflets rarely more than 15, entire or deeply 2-3-lobed; petals unblotched: 3. P. ostii

5. Paeonia ostii T. Hong & J. X. Zhang, Bull. Bot. Res. (Harbin) 12 (3): 223, fig. 1 (1992). Typus: China, Zhengzhou Institute of Aeronautical Industrial Management, Arboretum of Rare and Endangered Trees, introduced from Mt. Yangshan of Songxian, Henan Province.....P. suffruticosa subsp. ostii (T. Hong & J. X. Zhang) J. J. Halda, Acta Mus. Richnov., Sect. Nat., 4 (2): 30 (1997); P. suffruticosa subsp. yinpingmudan D. Y. Hong, K. Y. Pan & Z. W. Xie, Acta Phytotax. Sin. 36 (6): 519, fig. 2, pl. 2.......Shrub to about 1.5 m tall. Leaves biternate or bipinnate with three pinnae, leaflets 9-15, more or less lanceolate with acuminate tip, entire or sometimes 2-3-lobed, greyish-green, especially when young. Flowers large (c. 15 cm diam.), single, petals white, often flushed with purplish-pink, unblotched, disc dark reddish-purple.
Recorded as growing wild in Henan, Anhui, Hunan and Shaanxi, but possibly now extinct as a genuinely wild plant except in western Henan. Perhaps still common in cultivation, especially in Anhui, but many cultivated plants similar in appearance to this species may be hybrids between it and P. X suffruticosa. Plants cultivated under the name 'Feng Dan Bai' (='Phoenix White') may be the true species, but at least some appear to be hybrids.

(2001)  
 
KEY TO SPECIES
1. Flowers solitary, erect; disc leathery, sheathing the carpels to at least half their length (Section Moutan DC.): 2
2. Carpels 5(-7), tomentose, more or less entirely sheathed by the disc; leaves biternate or 2-3-pinnate, leaflets 9-33: 3
3. Small shrubs to not more than c. 1.2 m tall; leaves more or less biternate, leaflets usually 9, sometimes 11-15, ovate to suborbicular; flowers comparatively small, c. 10 cm in diameter: 4
4. Lateral leaflets often entire, terminal leaflets usually shallowly 3-lobed, often reddish above; petals often with a red basal blotch: 2. P. qiui

2. Paeonia qiui Y. L. Pei & D. Y. Hong, Acta Phytotax. Sin. 33 (1): 91, fig. 1 (1995). Typus: China, Hubei, Shennongjia, Songbai....P. ridleyi Z. L. Dai & T. Hong, Bull. Bot. Res. (Harbin) 17 (1): 1, fig. 1 (1997); P. suffruticosa subsp. spontanea (Rehder) Haw & Lauener var. qiui J. J. Halda, Acta Mus. Richnov., Sect. Nat., 4 (2): 31 (1997)...... A small shrub to about 80 cm tall. Leaves bitemate, leaflets 9, reddish-purple above, ovate to almost circular, lateral leaflets often unlobed, terminal leaflets usually trilobed. Flowers single, rather small (c. 10 cm diam.), petals pink or rose, often with a red basal blotch, disc dark reddish-purple......Hubei (Shennongjia mountain, region) and Henan (Xi Xia).

(2001)  
 
KEY TO SPECIES
1. Flowers solitary, erect; disc leathery, sheathing the carpels to at least half their length (Section Moutan DC.): 2
2. Carpels 5(-7), tomentose, more or less entirely sheathed by the disc; leaves biternate or 2-3-pinnate, leaflets 9-33: 3
3. Shrubs often at least 1.5 m tall; leaves more or less 2 - 3-pinnate, leaflets 11-33, ovate to lanceolate; flowers comparatively large, more than 10 cm in diameter: 5
5. Leaflets (17-) 19-33; petals with a prominent dark purple basal blotch: 4. P. rockii

5. Paeonia rockii (S. G. Haw & L. A. Lauener) T. Hong & J. J. Li ex D. Y. Hong, Acta Phytotax. Sin. 36 (6): 539 (1998). Typus: China, Kansu.... P. rockii T. Hong & J. J. Li, Bull. Bot. Res. (Harbin) 12 (3): 227, fig. 4 (1992), nom. inval. (lacking exact page reference of basionym); P. suffruticosa subsp. rockii S. G. Haw & L. A. Lauener, Edinb. Journ. Bot. 47 (3): 279, fig. la (1990)....P. suffruticosa 'Rock's Variety' ('Joseph Rock') hort..... Shrub to about 2 m tall. Leaves more or less triternate or 2-3-pinnate, with 19-33 leaflets, rarely less than 19 but always more than 15. Flowers very large (15-20 cm diam.), single; petals white, sometimes flushed with pink, with a conspicuous deep purple basal blotch, disc whitish.

KEY TO SUBSPECIES
Leaflets lanceolate to ovate-lanceolate, often entire or sometimes 2-3-lobed:
5a. P. rockii subsp. rockii. P. rockii subsp. linyanshanii T. Hong & G. L. Osti, Bull. Bot. Res. (Harbin) 14 (3): 237, fig. 1 & 2 (1994); P. suffruticosa subsp. rockii S. G. Haw & L. A. Lauener var. linyanshanii (T. Hong & G. L. Osti) J. J. Halda, Acta Mus. Richnov., Sect. Nat., 4 (2): 30 (1997). ...Leaflets lanceolate or ovate- lanceolate, entire or sometimes 2-3-lobed. ...Southern Gansu, southern Shaanxi (on the southern slopes of the Qinling Mountains), Henan (Funiu Mountains) and western Hubei.

Leaflets ovate to suborbicular. mostly 2-5-lobed:
5b. P. rockii subsp. taibaishanica D. Y. Hong. Acta Phytotax. Sin. 36 (6): 542, fig. 2 (1998). Typus: China, Shaanxi, Mt Taibai, Shangbaiyun, alt. 1750 m., in broad-leaved deciduous forest on cliff, 24 v 1985...Leaflets ovate to suborbicular, mostly 2-5-lobed..... Found only on the northern slopes of the Qinling Mountains in southern Shaanxi and Gansu. Reported to have been common on Mt Taibai in the 1960s, but now scarce.

(2001)  
 
The recognition of P. jishanensis T. Hong & W. Z. Zhao as a distinct species seems to me to be correct. There is, however, a problem regarding the name of this taxon. When Hong and Zhao published this name in Hong, T. et al. (1992: 225 - 226, 232).... they went on to say: "On the basis of specimen no. 338 collected by W. Purdom in 1910, 50 li west of Yan'an, A. Rehder, the American taxonomist of woody plants, published a new variety of tree peony (i.e. P. suffruticosa Andrews var. spontanea Rehd.). The original Latin diagnosis of this variety described the flowers as pink, sometimes with petaloid stamens (Journal of the Arnold Arboretuni 1: 193, 1920). In 1990, the British scientists S.G. Haw & L. A. Lauener raised A. Rehder's variety to a subspecies, P. suffruticosa Andrews subsp. spontanea (Rehd.) Haw & Lauener, and included the wild tree peony with white flowers from Majiagou, Ji Shan, Shanxi province in this subspecies. The authors' opinion is that P. suffruticosa subsp. spontanea has petaloid stamens, which are an important characteristic developed after domestication of a wild tree peony, so that therefore P. suffruticosa subsp. spontanea should be reduced to the status of a cultivar, 'Spontanea'.".....This, however, is an error. There is no reason at all why a cultivated plant cannot be the type specimen of a taxon. The type of this taxon must be Purdom 338. The name P. jishanensis, typified by Hong Tao 915010, is, therefore, superfluous and illegitimate.

(2001)  
 
KEY TO SPECIES
1. Flowers solitary, erect; disc leathery, sheathing the carpels to at least half their length (Section Moutan DC.): 2
2. Carpels 5(-7), tomentose, more or less entirely sheathed by the disc; leaves biternate or 2-3-pinnate, leaflets 9-33: 3
3. Small shrubs to not more than c. 1.2 m tall; leaves more or less biternate, leaflets usually 9, sometimes 11-15, ovate to suborbicular; flowers comparatively small, c. 10 cm in diameter: 4
4. Leaflets deeply 3-lobed and toothed, green above; petals unblotched: 1. P. spontanea