Paeonia ludlowii (Stern & G. Taylor) D.Y. Hong

An adaptable garden plant, Paeonia ludlowii is a medium to large shrub forming a dense clump of tall unbranched stems with excellent, finely cut foliage. The yellow flowers, 10 cm across, appear in May in western Europe; on a good specimen they are copious and impressive (Bean 1976). First described as a variety of P. lutea (which is now regarded as P. delavayi f. lutea), and often still referred to as ‘P. lutea ludlowii’, it has overtaken that less showy plant to become the commonest yellow-flowered woody peony in European gardens.

P. ludlowii is endemic to a small upland area of southeastern Tibet, near the Tsangpo Gorge. The relatively modest rainfall of this area by western Chinese standards, 1 m or less annually, may help explain its tolerance of much drier climates in Europe and North America, and of dry soils, even on chalk (Stern & Taylor 1953). It is closely related to the much more widespread and variable P. delavayi, differing in its much taller, unbranched stems; its larger, more widely open flowers, always yellow (also several weeks earlier in cultivation); and in its usually having only one carpel per flower (Hong 2010). Molecular data support the idea that a small, linked group of relict populations has diverged from P. delavayi through long isolation in this area, in which it may have persisted through periods of glaciation elsewhere (Zhang et al. 2018). Digging of the roots for medicine poses a significant threat to this very local species (Hong 2010).

It became known to Western science through herbarium specimens and seed collected by the British plant collectors Frank Ludlow and George Sherriff, as well as by Frank Kingdon-Ward, from the mid-1930s onwards. Introduction to cultivation came through Ludlow & Sherriff’s seed collections L&S 1376 of 1936, LS&T 6392 of 1938 and LS&E 13313 of 1947, each from a different population within this area (Stern & Taylor 1953). There appears to have been an independent introduction to Birr Castle, Ireland, by the 6th Earl of Rosse, who travelled in China in the mid-1930s (Adams 2010).

Unlike P. delavayi, P. ludlowii seems unable to produce new, independent plants vegetatively in the wild, reproducing only by seed (Hong 2010). This is also true in cultivation, where seed is the normal means of propagation (Stern & Taylor 1953, Bean 1976). It is not clear whether poorly flowering specimens are the result of seedling variation or of too moist or too fertile soils (Bean 1976).

This species is so widely planted and sold by nurseries in western Europe that it seems pointless to single out good examples. Being seed-propagated, few can be directly traced to a wild introduction; there are however specimens from LS&E 13313 at RBG Edinburgh and Benmore Botanic Garden, Scotland (Royal Botanic Garden Edinburgh 2020a). It is a far less common plant in North America, and may not be sufficiently hardy for colder central areas. Bremer (2019) notes that in Wisconsin (zone 4b) aerial stems are normally killed by cold in winter. Nevertheless, it is recorded from Denver Botanic Gardens and the Betty Ford Alpine Gardens, at significant altitude in Colorado (Royal Botanic Garden Edinburgh 2020b).

Like P. delavayi, P. ludlowii does not have a long history of cultivation in Asia, and has not contributed to the breeding of Chinese woody hybrids (Cheng 2007). A very few hybrids have appeared among seedlings of P. ludlowii in Western gardens. ‘Anne Rosse’, a hybrid with P. delavayi, is the best known (see Paeonia Hybrid Cultivars including P. delavayi); other breeders have reported similar seedlings (Burkhardt 2008). As with P. delavayi f. lutea, wider hybridisation by contemporary breeders is to be expected.