Paeonia officinalis((Hong, De-Yuan. “Peonies of the World. Taxonomy and phytogeography.” Kew: Royal Botanic Gardens, 2010, pp. 230-239.))
Perennials. Roots tuberous-thickened. Caudex short, less than 10 cm long. Stems mostly hirsute, green or purple—red, 25—80 cm tall. Lower leaves biternate, with 9 leaflets; petioles 6-12 cm long, mostly hirsute; petiolules 1-6 cm long, mostly hirsute; leaflets usually segmented; leaflets/leaf segments 11-130 in number, linear-elliptic to elliptic, or oblanceolate, cuneate at the base, acuminate or acute at the apex, lobed or entire, 3—12 cm long, 1-4.5 cm wide, glabrous above, villose, rarely glabrous beneath. Flowers solitary, terminal; involucrate bracts 1—2 in number, leaf-like, relatively distinct from sepals; sepals 3—5 in number, deltoid-orbicular to orbicular, 1-2.5 cm long, 0.8-2 cm wide, mostly rounded at the apex, hispidulous or glabrous on the abaxial side; petals 5—8 in number, pale violet-red or purple-red; ﬁlaments purple; anthers yellow; disk up to 1 mm high, flat or waved, red; carpels 1—5, mostly 2—3, in number, tomentose or glabrous, hairs 1.5-2 mm long, yellow, brown or pink; stigmas sessile, red, c. 1.5 mm wide. Follicles long—ovoid when young.
Chromosome number: 2n = 20 (see each subspecies for additional information).
Widely distributed from the Iberian Peninsula to the Balkans via France, Italy and Switzerland.
Paeonia officinalis is the typical species of the genus Paeonia, but its circumscription was not clear and it was confused both with P. peregrina (de Candolle, 1818, 1824; Baker, 1884; Lynch, 1890; Huth, 1891), until the work of Stapf (1918), and with P. mascula (e.g. Fiori, 1898). The species is extremely variable because of great variation in natural populations and extensive cultivation, as demonstrated by the more than 20 specific and many infraspeciﬁc synonyms included here. For example, the entity in the Iberian Peninsula and SW France has leaflets/leaf segments numbering more than 50, which are mostly lobed, whereas that in the Balkans has no more than 24 leaflets/leaf segments, which are mostly entire. In the Iberian Peninsula and SW France, the great majority of carpels are glabrous (over 90%), whereas they are totally tomentose in all the other populations. However, the peony here circumscripted cannot be clearly split, and all the differences, even the clear ones mentioned above, are bridged by intermediate forms. Paeonia officinalis is morphologically polytypical with its types closely correlated with geography.
Five types could be recognised and are treated here as five subspecies.
1a. Carpels glabrous, occasionally sparsely hirsute; sepals mostly glabrous; leaflets/leaf segments usually obtuse at the apex, often lobed; stems mostly glabrous: subsp. microcarpa
1b. Carpels tomentose; sepals usually pubescent; leaflets/leaf segments usually acuminate at apex, entire, rarely lobed; stems hirsute or glabrous.
2a. Leaflets/leaf segments 11—24 in number, 2—4.5 cm wide, glabrous or sparsely villose beneath; sepals glabrous or sparsely pubescent: subsp. banatica
2b. Leaflets/leaf segments 19—130 in number, 1—3 cm wide, always villose beneath; sepals always pubescent.
3a. Leaflets/leaf segments 35-130 in number, always with some lobed, 1—2 cm wide: subsp. huthii
3b. Leaflets/leaf segments 19-45 in number, all entire or occasionally very few lobed, 1-3 cm wide.
4a. Leaves villose-floccose beneath, hairs flattened at base: subsp. italica
4b. Leaves hairy but never villose-floccose beneath, hairs cylindrical: subsp. officinalis
Paeonia officinalis subsp microcarpa
Chromosome number: 2n = 20 (tetraploid)
Growing in pine woods or in thickets in limestone areas at altitudes from 400 to 2,050 m. Distributed in Portugal, Spain and SW France.
Paeonia officinalis subsp. microcarpa is rather distinct from the other four subspecies of P. officinalis in having carpels glabrous, or very rarely hirsute. Among 89 ﬂowers examined, only 6 have carpels that are sparsely hirsute and one has moderately hirsute carpels; by contrast carpels in the other four subspecies are all tomentose. Sepals are usually glabrous or sparsely hairy in this subspecies, also contrasting with the others. In addition, the leaflets/leaf segments in this subspecies are generally more numerous than those in the other four subspecies and are often lobed. Seeds ellipsoid, black, 7-8 mm long, 5-6 mm wide.