Picea morrisonicola Hayata

When Picea morrisonicola was discovered on Yu Shan (Taiwan’s highest mountain, known throughout the English speaking world during the 19th and 20th centuries as Mount Morrison) in 1900 it instantly became the southernmost member of its genus. Spruces later discovered in Mexico extended the distribution of the genus to a new southern limit in the Americas, but none of the Mexican taxa extend quite so far south as the Taiwan Spruce which comes within a few kilometres of the Tropic of Cancer at 23°27’N (Debreczy & Rácz 2011).

Hayata described Picea morrisonicola to science in 1908 and it was introduced to western cultivation by E.H. Wilson in 1918. Wilson’s seed was widely distributed (Wilson 1919) but this species has always been rare in cultivation, particularly in North America where it is almost unheard of. It is only marginally more frequent in western Europe, and even in the UK and Ireland it is only seen in specialist collections. Like most Taiwanese conifers P. morrisonicola balked at a continental climate, but even in oceanic climate zones it would prove fickle, succeeding only where winters are not excessively cold and where the summers combine high humidity and precipitation. In western Europe the island of Ireland would prove perhaps the most hospitable environment, and in 2024 seven of the ten tallest and largest trees recorded by the Tree Register of Britain and Ireland are distributed in Counties Down, Meath, Offaly and Wicklow, including the champion for girth at Castlewellan, Co Down, 21 m × 75 cm dbh in 2015; other sizeable trees grow at Birr Castle, Headfort and Mount Usher. The tallest on record throuhgout this area grows at Stanage, Wales, 22 m × 64 cm in 2023. A remarkable and unlikely record, of a tree 19 m × 52 cm in 2018, comes from the pinetum at Tannadyce in Angus, Scotland, where the climate ought to be quite unfavourable (Tree Register 2024).

Wilson’s introduction, and propagations of original trees, seem to have been the source of most plantings through to the 1970s, when the Taiwan Forest Research Institute (TFRI) began distributing seed via its Index Seminum. These were supplemented, at least in a UK and Ireland context, when the late Chris Page introduced seed in 1976 (Page 10059, growing at Benmore Botanic Garden, Argyll, and in several collections in Devon and Cornwall) followed in 1993 by Kirkham & Flanagan 67 and Edinburgh Taiwan Expedition 193, neither of which resulted in large numbers of plants, and TFRI sendings continued to be an important source of new material up until the early 2000s (Royal Botanic Garden Edinburgh 2024).

Even in favourable climatic conditions Taiwan Spruce grows slowly at first, as historic records attest: a tree planted at Birr Castle (Offaly, Ireland) in 1928 was 11.8 m × 28 cm in 1966, 18 m × 32 cm in 1985, and 20.4 m × 53 cm in 2024 (Mitchell 1972; Clarke 1988; Tree Register 2024). After planting Picea morrisonicola can spend many years increasing slowly in height but pushing out wide-spreading branches and developing a dense, even bushy habit; when the plant is ready its height growth will then suddenly accelerate, with trees developing a broad-pyramidal outline as they increase in height. The steeply ascending, widely spaced whorls of first order branches give young trees a soft outline and distinctive overall appearance.

After seeing this species on Yu Shan in 1918, Wilson described it as ‘decidedly sombre’ in its general aspect (Wilson 1919). Others have imitated his view ever since, describing it as pale, grey and ghostly. This view is generally formed on account of Taiwan Spruce’s pale, grey-green leaves that are usually matt, not glossy, pressed down along the shoot and beneath it, and the nodding second order branches and branchlets. In sheltered situations the crown can be rather dense, but exposure quickly renders them rather sparse (pers. obs.).

Historically Picea morrisonicola has been compared with P. glehnii but the two could scarcely be more different. In details of its foliage it is most likely to be confused with P. wilsonii from west-central China; the two share remarkably pale, almost white shoots, but P. morrisonicola differs in having leaves on leading shoots swept strongly forward above the shoot and depressed at the side and beneath. In this respect, and with the single leaf protruding at a wide angle from beneath lateral buds, P. morrisonicola also resembles P. obovata, but that species differs in its wider leaves, darker often slightly pubescent shoots, the dense crown and the narrowly pyramidal to columnar profile (Mitchell 1972; Bean 1976).

Recent phylogenetic studies have failed to resolve the position of Picea morrisonicola. It is consistently placed in a clade containing other Asian species (e.g. P. brachytyla, P. likiangensis, P. wilsonii) (Ran, Wei & Wang 2006; Lockwood et al. 2013; Sullivan et al. 2017; Feng et al. 2018; Shao et al. 2019) but these studies have not resolved the interspecific relationships within this clade, which, for some authors, also includes some North American taxa. Bodare et al. (2013) found P. morrisonicola clusters most closely with P. wilsonii, and date the divergence of these species to between 4 and 8 million years ago, which coincides with the formation of Taiwan (4–5 mya).