Although this is neither the largest nor the most diverse group of Chinese woody hybrids, it is the best suited to much of our area. Usually taller than the Central Plains cultivars, many can ultimately reach 2–3 m. They are potentially very long-lived shrubs. Most have hairy leaves, usually tinted red or purple as they emerge. 15 or more leaflets is usual, although a few have 9; leaflet shape is very varied. Flowers are large, usually held upright and above the leaves. Petal colour varies widely in the pink-red-purple area; there are whites, occasionally creamy yellow, and various bicolors. A basal blotch is the norm, typically dark red to black, often showing through on the back, and especially conspicuous in single-flowered varieties. The disc sheathing the carpels varies in colour. The filaments are usually pigmented. Flowers usually have a strong, pleasant scent. Several types of flower form are known in this group (Wang 1998; McLewin & Chen 2006).
These cultivars originated in central Gansu Province and neighbouring areas, which have a semi-arid continental climate with long, cold winters and dry summers. Their primary wild ancestor is P. rockii, which has been cultivated in the area, for medicine, for more than 1,000 years, with further genetic input from Central Plains cultivars (Cheng 2007). There is historical evidence of the existence of hybrid cultivars here by the 16th century (Li 2005). 200–300 cultivars are now known (McLewin & Chen 2006; Cheng 2007). Development continues; Heping nurseryman Chen Dezhong has been pre-eminent in selection of new varieties (McLewin & Chen 2006; la Pivoine Bleue 2008). Relatively large nurseries exist, but commercial production also takes place on a smallholding scale. Commercial propagation is primarily by grafting, usually onto a herbaceous stock, which can be removed once the woody scion has produced its own roots (McLewin & Chen 2006).
It should be noted that Paeonia Gansu Group has been proposed, initially in China, as a formal taxon, covering all woody peonies with a dark or purple flare on the petals, regardless of the origin (see McLewin & Chen 2006). It follows that wild P. rockii, most Gansu cultivars, plus some Central Plains and other cultivars would be included. This might prove necessary in a ‘watertight’ classification, but runs counter to our aim here of an explanatory treatment.
Our understanding of these plants in Western gardens has been distorted by ignorance and myth surrounding various Gansu Mudan introduced as seed by Joseph Rock – the story has been well researched and unpicked by McLewin & Chen (2006). Rock had a better understanding of Chinese language and culture than most Western plant-collectors of his day, but unfortunately seems to have had little interest in peonies. He sent three batches of woody peony seed to Charles Sargent of the Arnold Arboretum during the winter of 1925–1926, as an addendum to the main seed collections from his expedition to Gansu. These were apparently collected by others from cultivated plants in the lamasery garden at Zhouni (spelt ‘Choni’ by Rock), Gansu, and in the garden of the local ruler. Sargent distributed the seed among several North American and European gardens. They produced single-flowered plants, with white or pink-blushed petals with a dark blotch. Although not uniform, they collectively attracted names such as Paeonia ‘Joseph Rock’, P. ‘Rock’s Variety’, or simply P. rockii or P. suffruticosa subsp. rockii. Almost any reference to any of these names in the horticultural literature should be taken to refer to these Rock-derived Gansu hybrids in general (McLewin & Chen 2006); only now are gardening books beginning to catch up (Edwards & Marshall 2019).
A beautiful specimen in Sir Frederick Stern’s garden at Highdown, Sussex has been especially coveted by British gardeners since the mid-20th century; even today, knowledgeable British gardeners who are not peony specialists, seeking plants under the names listed above, usually seem to be after something that looks exactly like Stern’s plant (J. Sutton, pers. obs.). As the (1946) monographer of the genus, Stern was central to the myth created around these plants (McLewin & Chen 2006). Despite never acknowledging it in his publications, Stern’s plant was not a Rock ‘original’; rather, it was apparently a seedling, sent by the Canadian plantsman F. Cleveland Morgan in 1936 – Morgan had raised a single plant from the original seed distribution ten years previously. Stern seems to have been keen to believe in its status as a wild plant, including it in his (1946) concept of P. suffruticosa. He made much of Rock’s opinion stated in a 1938 letter to Stern, that it ‘looked… like a wild plant’, although Rock made clear that he ‘never came across it in a wild state.’ Stern later embellished the facts, claiming that ‘the lamas told him [Rock] that it came from the mountains of this district’. Seedlings, many rather similar, were raised and distributed from Highdown, ending up in Britain, continental Europe and North America, with this story attached. The presumed original Highdown plant, along with its vegetative progeny, has been given the clonal name ‘Highdown’ (there are good plants of this at RHS Garden Wisley and the Savill Garden); ‘Joseph Rock’ is now attached to a rather similar plant, well distributed clonally in North America (McLewin & Chen 2006). Other clones are best thought of as unnamed Gansu hybrids. Named cultivars and others continue to be imported from Gansu in a small way by specialist nurseries in Europe and North America; only a representative selection is described below. For many more cultivars see McLewin & Chen (2006), Li (2005) and commercial websites such as The Tree Peony Company (2020).
These are ecologically adaptible plants. A deep, fertile, well-drained but not dry soil in a more or less sunny position, with good air movement is ideal, but they will tolerate a great deal of deviation from this (McLewin & Chen 2006). Highdown has a thin chalk soil, for example, where their tolerance of summer drought is important. There is general agreement among specialist growers that they are far better suited to western Europe and much of North America – even the Midwest and the South, from zone 4 to 9 – than the Central Plains varieties (McLewin & Chen 2006; Buchite 2019; Austin 2020; Cricket Hill Garden 2020).
Gansu hybrids can become large plants, sufficiently impressive for three weeks of the year that there is a temptation to plant them even though too little space is available, then to keep them in check by pruning. We leave the last word on this to McLewin & Chen (2006): ‘a large Gansu Mudan growing strongly will react well to almost any pruning but such a plant is so magnificent that what is appropriate is cautious, careful sympathetic pruning or none at all.’
Single or Semi-Double (lotus) form; petals reddish-purple with black flares; flowering mid-season; habit somewhat spreading. Selected by Chen Dezhong; the name translates as ‘icy purple heart’ (Li 2005; McLewin & Chen 2006; Tree Peony Company 2020).
Single, with flowers to 17 cm across, mid-season; petals a peachy reddish-pink with dark purple flares. Selected by Chen Dezhong; the name translates as ‘phoenix wings high in the sky’ (Li 2005; Tree Peony Company 2020).
Semi-Double (crown) form, flowers to 16 cm across; petals pink-flushed red, with small dark purple flares; vigorous, mid-season flowering, with a somewhat spreading habit. Selected by Chen Dezhong; the name translates as ‘phoenix crown with jade pearls’ (Li 2005; Tree Peony Company 2020).
Single, with fragrant flowers to 17 cm across, mid-season; petals a non-uniform light pink, finely veined towards the margins, with purple flares. Selected by Chen Dezhong; the name translates as ‘pink lotus’, although there is no question of it having Lotus form (Li 2005; McLewin & Chen 2006; Tree Peony Company 2020).
A very full Semi-Double, classified as Globular by Li (2005) although it has both stamens and carpels and as Crown by The Tree Peony Company (2020); large, fragrant flowers to 18 cm across, mid-season; petals light pink with red-brown flares; annual stems rather short and stout. A traditional cultivar grown in Linxia and Lintao, Gansu; the name translates as ‘pink beauty’ (Li 2005; Tree Peony Company 2020).
Full Double (Globular), with fragrant flowers to 18 cm across, late season; petals white streaked bluish-pink, with purple flares. Selected by Chen Dezhong; the name translates as ‘Heping (= ‘peace’) twin beauties’ (Li 2005; McLewin & Chen 2006; Tree Peony Company 2020).
Single to about 20 cm across, with about 10 petals in two whorls, pale pink in bud, opening pale pink inside but ageing white, quickly in sun; flare deep blackish-purple, to 4.5 cm long, showing faintly on the backs; filaments dark purple, with white bases; lightly fragrant, reminiscent of roses. Young foliage flushed reddish-bronze. Makes a rounded shrub to 2 × 1.5 m in 10 years. The name applies only to plants propagated clonally from Stern’s famous specimen at Highdown (see above), which have had a modest commercial distribution in Britain; there are good specimens at Wisley and the Savill Garden.
This name has been used rather vaguely in the past, but is applied by McLewin & Chen (2006) to a single clone widely distributed in North America by the Klehm family’s Illinois nursery (later Song Sparrow Nursery, WI). It seems to be derived ultimately from Stern’s stock at Highdown, by way of David Reath, Michigan; at which stages seed-raising was involved is not clear. It differs from ‘Highdown’ in having uniformly green leaves, very little pink in the flowers, and white filaments with red-purple bases. However, the primary difference between these similar-looking plants is provenance McLewin & Chen (2006).
Semi-Double (Rose form), flowering mid-season; petals pink, paler toward the margins, with red flares. Selected by Chen Dezhong; the name translates as ‘Gansu plateau twin beauties’ (McLewin & Chen 2006; Tree Peony Company 2020).
Single, white with dark red flares, mid-season; vigorous. Selected by Chen Dezhong. The name translates as ‘snow sea icy heart’; the element xue hai (literally ‘snow sea’) could metaphorically imply a sea of cloud or a range of snowy mountains (Li 2005; McLewin & Chen 2006; Tree Peony Company 2020).
Single, with large fragrant flowers mid-season; petals maroon with black flares; fast growing, with spreading stems. Selected by Chen Dezhong; the name translates as ‘purple butterfly facing the wind’ (Li 2005; McLewin & Chen 2006; Tree Peony Company 2020).
Semi-Double (lotus) form, flowers to 16 cm across, fragrant; petals purple with large black flares; fast growing and early flowering. Selected by Chen Dezhong; the name translates as ‘purple ink stone’ (Li 2005; McLewin & Chen 2006; Tree Peony Company 2020).