Herbs perennial. Roots thick, cylindrical or carrot—shaped, attenuate toward tip, up to 30 cm long, 2 cm in diameter. Stems up to 1 m tall, glabrous, very occasionally hispid. Lower leaves biternate; terminal leaﬂets often 2- or 3—segmented; leaﬂets/leaf segments 10-15, rarely 9 in number, lanceolate or ovate-lanceolate, cuneate or decurrent at the base, acute at the apex, 4.5—16 cm long, 1.5—6 cm wide, usually with bristles along veins or sometimes glabrous above, glabrous or sparsely pubescent along veins beneath; margins white cartilaginous-thickened, dentate—spinose on the thickenings. Flowers usually 3—4 on a stem, both terminal and axillary, sometimes only the terminal one developed with 2—3 axillary sterile buds, very rarely solitary without sterile ﬂower buds, single (in wild populations) or double (in cultivated plants), 8—13 cm across; involucrate bracts 4 or 5 in number, unequal, leaf-like; sepals 3 or 4 in number, broadly ovate or suborbicular, 1—2 cm long, 1-1.7 cm wide, all caudate at the apex; petals 9-13 in number, white or pink (in wild populations), or various in colour (among cultivated plants), obovate, 3.5—6 cm long, 1.5—4.5 cm wide; ﬁlaments yellow; anthers yellow; disk yellow or red, 1—5 mm high, waved or incised; carpels 2-5 in number, green, red or purple, glabrous or rarely sparsely hispid or tomentose, with hairs 1-1.5 mm long; stigmas sessile, red, 1.5—2.5 mm wide. Follicles ovoid or oblong-ellipsoidal, 2.5-3 cm long, 1.2-1.5 cm in diameter. Seeds black, ovoid- spherical, 7 mm long, 6 mm in diameter.
Chromosome number: 2n=10
Growing in bushes and grasslands, but also in open woods, at altitudes from lowlands to 2,300 m, but to 3,400 m in Sichuan Province (Kangding), China. In E Asia: China, the Korea Peninsula, E Mongolia, and Russia (the Far East and SE Siberia).
The most distinct character of Paeonia lactiflora is the cartilaginous thickening along the leaf margins, which are dentate—spinose on these thickenings. Historically, the crossing experiment conducted by Saunders and Stebbins (1938) demonstrated that this species was incompatible with P. anomala, P. Veitchii, P. emodi, and four other species, and thus seemed in a very isolated position. However, our unpublished molecular data (CPAT, Adh1 and Adh2) imply that the species is closely related to P. emodi. In the subsection Albiﬂorae, P. emodi and P. lactiflora have fewer leaflets/ leaf segments.
Petals and carpels in Paeonia lactiﬂora are rather variable in colour in wild populations. The former were found varying from pure white, whitish pink to pink, whereas the latter varied from green, pink, red, purple to dark purple even within a single population. We found both glabrous and pubescent carpels within populations, and therefore P. albiflora var. trichocarpa Bunge is here treated as synonymous to P. lactiflora.
This species is widely cultivated for both ornamental and medicinal purposes. Flowers are always doubled in cultivated varieties of Paeonia lactiflora.
- Hong, De-Yuan. “Peonies of the World. Taxonomy and phytogeography.” Kew: Royal Botanic Gardens, 2010, p. 111.