Paeonia ostii T. Hong & J.X. Zhang

There is an odd paradox around this species. While it is widely claimed as a wild plant (Hong 2010) and an important ancestor of hybrids (Wang 1998; Zhou et al. 2014), it is far clearer what this name means in practice among cultivated plants.

Plants fitting the above description are cultivated on a large scale in China, especially Anhui, for the outer layers of the root, which provide a traditional Chinese medicine, mudanpi (Hong 2010). Increasingly, they are also grown for peony seed oil, rich in unsaturated fatty acids, especially α-linoleic acid, and used nutritionally (Wei et al. 2018). These plants are known as Feng Dan (= Fengdan). Since the mid-1990s, such plants have been reaching Europe and North America from Chinese cultivation (Haw 2000); the usual white flowered ones are conventionally labelled ‘Feng Dan Bai’ (often marketed in North America as ‘Phoenix White’), and pink ones ‘Feng Dan Fen’ (‘Phoenix Pink’), as discussed under Southern Yangtze Cultivars. These are not clonal cultivars. Kees Sahin of K. Sahin Zaden B.V., a great peony lover, imported plants to the Netherlands from China in 2000, but the flowers produced once the plants had established were disappointingly small, at least in comparison to more familiar hybrid cultivars (J. Grimshaw, pers. comm. 2020). Hence, the easy availability of material will not necessarily result in this becoming a common garden peony.

Putative wild ancestors of Feng Dan are at best exceedingly rare, and the wild status of an individual is hard to prove, given long-term human interaction with wild woody peony populations. At any rate, the name P. ostii was published for them in 1992, and honours the Italian botanist Gian Lupo Osti, who investigated these plants. It is now usual in China to treat Feng Dan as a domesticated form of P. ostii (for example Wang 1998; Hong 2010; Zhou et al. 2014). While this treatment has been generally – if tentatively – adopted in Western horticulture (Haw 2000), there have also been sceptical voices (McLewin 2000). Genetic analysis suggests that domestication may have occurred several times in parallel (Peng et al. 2017). The stakes are high in terms of our understanding of the origins of cultivated peonies, since P. ostii has been invoked as one of the more important parents of ornamental hybrids in China (Wang 1998, Zhou et al. 2014). It seems highly likely that plants circulating in cultivation labelled (not incorrectly in these terms) P. ostii are Feng Dan rather than some ‘true’ pre-domestication form. Seed exchanges in Europe sometimes offer P. ostii: sometimes the resulting plants look like Feng Dan, sometimes they are quite different peonies.

There are issues around hardiness of this plant in parts of our area. In Gloucestershre, Haw (2000) found that buds began to break in December, the young shoots then being susceptible to frost. In Wisconsin, Bremer (2019) found that while it shared the summer heat tolerance of most woody peonies, it was very susceptible to cold, wet winters, when the stems are regularly killed.