Shrubs to 1.8 m tall, glabrous throughout. Stems up to 2 cm in diameter. Lower leaves mostly triternate-pinnate, ternate-bipinnate, biternate-bipinnate, with 29—65 leaflets; terminal leaflets elliptic to orbicular, 3-partite to the base or 3-fid, terminal lobes 3-lobed; lateral leaflets elliptic to orbicular, 3-lobed or coarsely toothed. Flowers solitary, terminal, 10—15 cm wide. Involucrate bracts 2—5, mostly 2 or 3, unequal, linear-lanceolate. Sepals 3—5, green, broadly obovate, all caudate at the apex. Petals 9—12, rose, obovate, 4-7 cm long, 3—5 cm wide. Disk leathery, enveloping half of carpels at anthesis, white or yellowish, with triangular teeth. Carpels always 5, very rarely 4 or 3, glabrous, green or purple; styles 1—2.5 mm long; stigmas red. Follicles black-brown when mature, ellipsoid. 2-4 cm long, 1.3—1.7cm in diameter. Seeds black, glossy, broadly ellipsoid or globose, 8—10 mm long, 6—8 mm in diameter.
Chromosome number: 2n = 10 (diploid).
Paeonia decomposita was observed to grow in thickets, young secondary forests or sparse coniferous forests with Cotoneaster soongaricus (Regel) Popov, Rosa willmottiae Hemsl., Berberis polyantha Hemsl., and Cupressus chengiana S. Y. Hu, as well as species of Lespedeza, Rhamnus L. and Quercus L., on cliffs and rocks at altitudes ﬁrom 2,050 to 3,100 m. This species is confined to the Dadu River Valley of northwestern Sichuan in China.
- Hong, De-Yuan. “Peonies of the World. Polymorphism and diversity.” Kew: Royal Botanic Gardens, 2011, p. 12.