Picea jezoensis (Siebold & Zucc.) Carrière

Picea jezoensis sensu lato

Picea jezoensis is widely distributed in northeast Asia, from 59°N on the Kamchatka peninsula and c. 56°N on adjacent parts of mainland Russia south to Korea on the mainland and central Honshu in Japan; it extends westward as far as Russia’s Stanovoy Range and Aldan Highlands and China’s Nei Mongol province (Farjon 2017). This range takes in several climatic zones, including true continental in the interior parts of the mainland, cold maritime in coastal districts of the mainland and Kamchatka, Sakhalin, and the Kuril islands, where the proximity of the sea tempers the climate somewhat, cold maritime to cold temperate on Hokkaido, and cold to montane temperate on Honshu (Debreczy & Rácz 2011).

An extensive distribution across several climate zones has resulted in much morphological variation that taxonomists have sought to define, largely through the publication of infraspecific names, but as is so often the case in conifer taxonomy there has never been agreement on how many constituents should be recognised and at which rank(s). In the west, and particularly in Europe, Honshu’s populations have long been considered distinct, usually distinguished at the rank of variety (var. hondoensis) e.g. Dallimore & Jackson (1966), Bean (1981), Krüssmann (1985), and Rushforth (1987). Such a view owes as much to the relative ecological isolation of Honshu’s populations (and their suitability for cultivation in western Europe) as it does any morphological distinctiveness.

Further subdivisions, especially of continental populations, have been more contentious. Debreczy & Rácz (2011) recognised three varieties in addition to the type, viz. var. hondoensis, var. komarovii and var. microsperma. The latter was recognised in the Flora of China account (Fu, Li & Mill 1999) but otherwise receives little credence, usually being lumped with the type, while var. komarovii, described orignially at species rank in 1950, gained acceptance for a while (e.g. Farjon 1990). More recently, however, Plants of the World Online (2024) has relegated the various permutations of the name komarovii to the synonymy of Picea jezoensis var. koreana Uyeki published in 1942, some eight years prior to the publication of P. komarovii and therefore taking precedence, but only when the rank of variety is considered to be the most appropriate.

Over time, the relatively minor morphological differences these names were founded on have been shown to correlate to distinct geographical (and thus ecological) origins. This has led to a preference for the rank of subspecies which is now used in favour of variety by Farjon (2017) who treats subsp. hondoensis, endemic to Honshu, and subsp. jezoensis which makes up the rest of the distribution. Almost all modern works further subdivide subsp. jezoensis to include at least one variety, usually var. komarovii (now correctly var. koreana) but a 2010 study into variation in cone morphology concluded there was no sound basis for recognising any infraspecific taxa, not even for populations on Honshu (Park et al. 2010), but the study did not consider other characters, nor the relative isolation of Honshu material from the rest of the distribution.

On balance it seems that Farjon’s (2017) view is the most sensible course, particularly in a work with a strong horticultural focus, so we recognise subsp. hondoensis but treat all other populations as part of a wide ranging and variable single entity, subsp. jezoensis. Were a further taxon to be recognised it would be more logical to treat it at the rank of subspecies than variety, in which case the correct name would be subsp. komarovii (V.N.Vassil.) Silba, but the characters on which additional splits have traditionally been justified are not taxonomically significant.

In maritime parts of our area, including much of western Europe and especially the UK and Ireland, this species is represented almost exclusively by the Japanese endemic subsp. hondoensis which is better suited to the prevailing maritime climate. Subsp. jezoensis is occasionally grown in these regions but rarely if ever makes good trees; it is much better suited to cultivation in areas with a strongly continental climate, but even in such regions the type has only a limited presence in western cultivation. The cultivars listed below were mainly selected in western Europe or in the Pacific Northwest of North America; we therefore assume that these are selections of subsp. hondoensis and place them accordingly.

Picea jezoensis subsp. jezoensis (sensu stricto)

Picea jezoensis subsp. jezoensis seems to have gained something of an ugly duckling reputation compared with the Hondo Spruce, subsp. hondoensis, but this says less about the tree than it does about the dominance of British dendrological literature through much of the late 19th and early 20th centuries. Writing from a British perspective Bean (1976) dismissed subsp. jezoensis as probably absent from cultivation and unsuitable in the UK climate. Both subspecies were introduced to Britain in 1861 by John Gould Veitch while von Siebold introduced subsp. jezoensis to the Netherlands in the same year (Jacobson 1996). Both collectors gathered subsp. jezoensis on Hokkaido, and while the fate of material raised in Holland is unclear, Veitch found the taxon to be an abject failure in Britain where it soon died out, while plants of subsp. hondoensis largely thrived (albeit one batch was unfortunately mixed with P. alcoquiana, and for some while the Veitch Nurseries distributed Hondo Spruce under this name) (Mitchell 1972). Later introductions of subsp. jezoensis to Britain, by Maries from Hokkaido and Wilson from Korea, probably fared little better (Bean 1976).

G.R. Hall introduced subsp. jezoensis to North America in March 1862. Again the fate of those early introductions is unknown, but it stands to reason that it should have fared better in continental North America than it did in western Europe. New Trees reported that a Frank N. Meyer collection made in Russia had been maintained in North American cultivation; in the mid 2000s this was ‘represented by a grafted tree of 11 m (32.5 cm dbh) at the Morton Arboretum, derived from an original tree in the Arnold Arboretum’ but by 2024 the Morton’s online catalogue made no mention of it, suggesting the material has died out (Morton Arboretum 2024). There is no trace of a Meyer collection in the Arnold’s database, either, but subsp. jezoensis is at least represented there by multiple plants derived from collections traceable to Changbai County, Jilin, China (NACPEC 97037) and Sarobetsu National Park, Hokkaido, Japan (Nicholson & Hay s.n.), and there is a single plant introduced as var. komarovii under a 1995 accession (47–95*B, see images) gathered on the NACPEC Expedition to Heilongjiang under the number HLJ 098 (Arnold Arboretum 2024). The collection notes tell us the parent was growing in ‘Wet upland woods with Betula costata, Betula platyphylla var. mandshurica, Vitis amurensis, Alnus sibirica, Corylus sp.’ (Arnold Arboretum 2024).

Subsp. jezoensis grows well in those parts of Europe with a continental climate, for example in central Germany where a tree in Schlosspark, Wiesenburg, has reached 17 m × 50 cm dbh by July 2024, its identity confirmed by images showing the pale whitish-yellow shoot (Monumental Trees 2024). There is a plot of subsp. jezoensis at Arboretum Mustila, Finland, planted in 1936 with twelve-year-old trees raised from seed gathered in Hokkaido; both this and a plot of subsp. hondoensis are in good health (Arboretum Mustila 2024). In another part of the same arboretum, preliminary results of a provenance trial suggest that ‘young plants from seed from the [Changbai] Mountains, on the border between Manchuria and Korea, start to grow in spring rather later than plants from other sources, which makes them hardier to spring frosts’ (Arboretum Mustila 2024). Material was also introduced to European cultivation under the name var. komarovii, by the 1994 University of Helsinki Botanic Garden Excursion to China which collected it in Antu County, Jilin, China. Among the recipients of material was the Royal Botanic Garden Edinburgh which sent several young plants to Dawyck in the Scottish Borders under the accession number 19951160. This cold site is perhaps as close as one gets to a continental climate in the UK, but even here these plants have struggled and display a general lack of vigour – the best remained a stubborn 50 cm tall ten years after planting! (Royal Botanic Garden Edinburgh 2024; Tree Register 2024).

The western European experience, of very high mortality rates in conifers introduced from continental north east Asia, is now quite familiar. Writing in New Trees John Grimshaw coined the phrase ‘Siberian conifer syndrome’ to describe the problem, whereby late spring frosts frequently injure or kill vulnerable young growth. The result is a stunted bush that at best grows a few centimetres a year, but spends most of its life looking dreadful, locked in a war of attrition with the presiding curatror, the curator waiting for the tree to die, the tree daring the curator to do the sensible thing and dig it up and put it on the bonfire. Siberian Fir, Abies sibirica, is perhaps the poster child for this group, which also includes species such as A. sachalinensis, Larix sibirica and Pinus sibirica.

Naturally there are just enough exceptions to this rule to encourage over-optimistic experimentation whenever material is available. During research for New Trees in the early 2000s the Tree Register of Britain and Ireland listed only a single, mature plant of subsp. jezoensis (Grimshaw & Bayton 2009) but by 2024 this had increased to several, albeit many of the identifications are tentative and are based on the improbability of subsp. hondoensis performing so poorly in Britain as these suspect trees (Tree Register 2024). One such example, on the Fairburn Estate in the Scottish Highlands, is noted as having a bright orange shoot which confirms this does indeed represent subsp. hondoensis – the shoot colour (pale yellow to yellowish-brown cf. distinctly orange) is diagnostic. A handful of younger trees recorded by the Tree Register represent more recent introductions, notably EHOK 20 from Hokkaido which has grown well at Kew, of all places, where three healthy trees were all c. 5.5 m tall × 11 cm dbh in 2022 (Tree Register 2024), rather outperforming others there from Sakhalin (ESUS 176) (Grimshaw & Bayton 2009). It must be stressed, however, that these are exceptions that prove the rule; the Royal Botanic Garden Edinburgh has successfully killed dozens of plants of subsp. jezoensis from such diverse provenances as Hokkaido, Sakhalin, Kamchatka, Jilin, and even North Korea, planted in a diverse range of locations including Benmore and Dawyck Botanic Gardens, and safe sites participating in the International Conifer Conservation Programme (Royal Botanic Garden Edinburgh 2024).