Picea koraiensis Nakai

Picea koraiensis belongs to a large clade of spruces that includes many Asian species, and also the European P. abies and Eurasian P. obovata (Ran, Wei & Wang 2006; Lockwood et al. 2013; Sullivan et al. 2017; Shao et al. 2019). Its Asian congeners include P. glehnii and the Japanese endemic P. koyamae, but a series of robust phylogenetic studies have confirmed its closest relatives are a group of species centred on P. asperata from western China. This is a vexatious species complex and it is introduced in greater detail in the article ‘Picea asperata aggregate’.

Variability between and among populations has prompted the publication of several names now treated as synonyms (see list and taxonomic note, above). Comparisons between spruce populations in Korea and northeast China with Picea koyamae of Japan began before P. koraiensis had even been described (Wilson 1916) and for many years the two were much confused in literature and collections. Chinese workers reduced P. koraiensis to a variety of P. koyamae in 1955; others have questioned whether it should belong in synonymy entirely, but it is distinct in several respects (Farjon 2017 and see below). Nevertheless P. koraiensis has suffered a series of identity crises ever since; many of the few examples in western cultivation were at one time labelled P. koyamae (Rushforth 1987; Jacobson 1996). Such cases of mistaken identity are not a thing of the past: seed received from Heilongjiang, China, in 1975 at Hørsholm, Denmark was still labelled P. koyamae in 2017 (1974020; University of Copenhagen 2024).

A further complication are spruce populations on so-called sandy lands in China’s Nei Mongol Province. In most major works on conifers (and in the Flora of China) these are treated as Picea meyeri; in regional Chinese treatments they are sometimes treated as a distinct taxon, P. meyeri var. mongolica or P. mongolica; in the past they have also been attributed to P. koraiensis (Xu, Li & Zheng 1994). During research for this account introductions of ‘P. koraiensis’ from Nei Mongol have proven to represent P. meyeri, but most collections are still erroneously labelled. Such plants have surely contributed to ongoing confusion around P. koraiensis and the other members of the P. asperata aggregate. This is clear to see at Dawyck Botanic Garden in the Scottish Borders where genuine P. koraiensis from Heilongjiang (19810575) and ‘P. koraiensis’ from Nei Mongol (19921086) differ markedly in their vigour, bark, leaf size and arrangement, and shoot characters (pers. obs.). The latter plant is problematic in that its (limited) provenance details place it closer geographically to P. koraiensis than to the nearest P. meyeri populations, but these could be a generalisation. This example notwithstanding, the spruce populations in northeasternmost China and adjacent parts of Russia and Korea would likely repay further investigation.

All of this makes it hard to be sure whether collections reporting Picea koraiensis are growing the genuine article. Certainly there are trees bearing this name in several collections in Europe and North America, spanning continental and maritime climate zones in both continents. However, the only confirmed trees seen by the author during research for this account include two at Dawyck, (19810575 from Heilongjiang) c. 8 m tall × 15 cm dbh and c. 10 m × 30 cm, and several at Benmore (19731141 unspecified wild origin; 19810564 from Jilin; (pers. obs. November 2024). They resemble other members of the P. asperata aggregate but differ in several details, in particular the leaves are more supple and are usually distinctly straight and green (apart from 19810564, in which they are curved and glaucous), the bark is relatively smooth (cf. exfoliating in irregular large flakes in P. asperata and small flakes in P. meyeri). From P. koyamae of Japan they differ in having longer, greener leaves (apart from 19810564), smoother bark, and larger buds not obscured by leaves at the shoot ends (pers. obs. November 2024).