Paeonia – from the Greek name paionia, for Paeon or Paion, physician of the gods and reputed discoverer of the medicinal properties of plants in this genus

Native range: Europe to E. Asia and in W. North America

Leaves:

• alternate, may be basal in herbaceous species
• usually at tops of shoots
• pinnately compound or simple and dissected
• ~ ternate (trifoliate or 3 leaflets)
• large

Flowers:

• ~ solitary
• terminal
• 5 sepals
• 5–9 petals
• ~ red, white, pink
• 1–12 leafy bracts
• many stamens
• large
• showy
• sometimes fragrant
• short lived

Fruit:

• cluster of follicles
• seeds have blue/black fleshy aril
• contains many infertile seeds

Other notes:

• herbs or shrubs
• pollinated by pollen-eating beetles
• with great ornamental and medicinal values, peonies were known as “king of flowers” in China and “queen of herbs” in Greece for over 1,000 years
• over 3,000 cultivars
• disjunct distribution of the genus may have resulted from interruption of the continuous distribution of ancestral populations of extant peony species across the Bering land bridge during the Miocene (23–5 MYA)
• Pleistocene glaciation may have played an important role in triggering extensive reticulate evolution (dependent on repeated intercrossing between a number of ancestral lineages)
• P. brownii and P. californica are two closely related species (or the same species, according to some authorities) that are endemic to Pacific western North America and have not been cultivated (and are not in the WA Park Arboretum collection)
• P. brownii grows in open, dry pine forests, sagebrush, mountain brush, and aspen groves at 200–3000 m. from WA (East Cascades & Blue Mtns) to CA, east to Montana and western states in between
  • self-compatible, and attracts insects by producing abundant floral nectar
  • primary pollinators are wasp queens, large flower fly, and burrowing bees
• P. californica grows in chaparral, edges of oak woodlands, and coastal scrub at 0–1500 m. elevation in Southern CA and Mexico (Baja California)
  • requires cross-fertilization

Ecology & Adaptations:

• Washington Park Arboretum hosts many hybrids and cultivars, including those named below:
  • P. delavayi, commonly known as tree peony, is a deciduous, multi-stemmed, woody shrub that typically grows to 3–5’ tall and as wide
    • P. delevayi refers to Father Jean Marie Delavay (1834–1895), French Catholic missionary who collected plants in China
    • native to open woodland areas and grasslands in western China from Sichuan and Yunnan to southeastern Tibet, growing primarily at altitudes of 9,000 to 11,000’
    • endangered species in its home range
    • large leaves are deeply divided into numerous lance-shaped to oval leaflets (entire leaf blade to 6–12” long)
    • leaves are dark green above and blue-green beneath
    • saucer-shaped flowers (to 3” across) which typically have maroon to dark red petals with red-purple anthers
    • self-incompatible
    • attracts pollinators with nectar and pollen and relies most on bees, beetles and ants for pollination
  • P. lutea (or P. delevayi var. lutea) features flowers with bright yellow petals and yellow anthers
    • lutea = yellow in Latin, referring to flower color
  • P. obovata, a small, shrubby herbaceous peony, is native to forested areas in Siberia, Manchuria, China and Japan
    • obovata = egg-shaped (being broader at the uppermost end), referring to the foliage
    • white to rose-purple blooms
    • biternate, gray-green foliage is divided into oval to broad- elliptic leaflets, with terminal leaflets being obovate
    • leaflets increase in size from point of flowering to point of seed maturity
  • P. suffruticosa grows on cliffs at 300 m. in Central Eastern China
    • suffruticosa means sub-shrub or somewhat shrubby
    • shrub to 1.5 m. tall
    • widely cultivated in China and elsewhere
    • terminal leaflets deeply 3-lobed, lobes again 2- or 3-lobes
    • some lateral leaflets 2- or 3-lobed, others entire
    • flowers white, pink, red, or red-purple
• plasticity of some species and cultivars in response to light gradient:
  • P. officianalis shade leaves are bigger than full-sun leaves, which increases light-capture area
    • high light-saturation points and light-compensation points in full sun are relatively high and decrease with increasing shade
    • under moderate shade (45–65% of full sunlight), net photosynthetic rates increase
    • with increasing shade, flowering rates and diameters decrease, and within several years, the plant becomes strictly vegetative with an increase in total leaf area
    • to “escape” shade, stems elongate.