Picea wilsonii Mast.

Picea wilsonii is an important tree across northern China, forming extensive forests from the eastern edge of the Tibet-Qinghai plateau in Qinghai and Sichuan, east through southern Gansu, Shaanxi and Shanxi to Hebei, and south to Hubei. Typically for such a widely distributed conifer, P. wilsonii has accumulated a plethora of synonyms as botanists have described new taxa based on differences which, with the benefit of hindsight, are dismissed as taxonomically inconsequential in modern works.

This spruce was named for E.H. Wilson at a relatively early stage in his career, in 1903, from material Wilson had himself collected in Fangxian, Hubei, in May 1901 during his first expedition to China (Wilson for Veitch 1897) (Farjon 2017; Sargent 1916). Augustine Henry had sent sterile specimens from the same locality in 1888, but apparently no botanist was confident enough to base a new species on this material and the description had to wait until Wilson’s more complete specimens arrived in western herbaria (Bean 1976).

Besides Wilson, other western collectors to introduce Picea wilsonii in the early 20th century included Frank Meyer, William Purdom and Joseph Rock. There are several original trees from Purdom 205 (Hebei, 1909) at the Arnold Arboretum, ranging in size from 51–65 cm dbh, and one from Purdom 806 (western Gansu, 1912) from 40–56 cm dbh, plus two young grafts; Meyer 256 (Shanxi, 1908) is represented by a single original tree, 42 cm dbh (Arnold Arboretum 2024). P. wilsonii suits a continental climate, and besides the Arnold trees there are fine examples in the botanic gardens in Gothenburg and Uppsala, Sweden (pers. obs.) and at Hørsholm, Denmark, where Rock’s collections are well represented (Wagner 1992).

In the UK and Ireland Wilson’s collections from the western part of the range, and particularly Sichuan, have grown well. Good trees are widely distributed throughout these islands, but the best include trees at Dawyck (24 m tall × 61 cm dbh in 2014, and others 21 m × 64 cm and 20 m × 58 cm in the same year); Hergest Croft (22 m × 61 cm in 2023 from a 1914 planting); Tannadyce (22 m × 51 cm in 2018, a somewhat glaucous tree); the Valley Gardens, Windsor Great Park (22 m × 44 cm in 2021); and Birr Castle (21 m × 63 cm from a 1913 planting) (Tree Register 2024).

New introductions since 1980 include multiple consignments of seed sent by the Chinese Academy of Forestry; young trees from these sendings are growing well in collections on both sides of the Atlantic. These ‘CAF’ sendings, as they are known, and particularly those of the early 1980s, infamously require careful scrutiny to be sure of their identification, and some seed lots included multiple taxa. At Dawyck Botanic Garden, Scotland, a group of trees raised from a seed lot received as Picea meyeri in 1980 has produced a few trees fitting that species, but two are clearly P. wilsonii (coming from a more strongly continental climate zone, these two plants have not grown nearly so well as Wilson’s Sichuan material did in its youth.) Conversely, SICH 114, introduced and widely distributed as P. wilsonii, is actually P. asperata (pers. obs. 2015–2024). Further recent introductions reported from North America include QLG 222 (from the 1996 expedition to Shanxi and Gansu) with young plants established in a few North American collections including the Morris Arboretum (Morris Arboretum 2024) and the from the NACPEC 2005 expedition to Gansu (NACPEC 05–079) (Morris Arboretum 2024), but neither of these collections was seen by the author in the preparation of this account.

At first glance Picea wilsonii is a rather anonymous looking spruce, generally resembling P. abies of Europe, but it is distinct in its glabrous, very pale, nearly white one- and two-year shoots. P. wilsonii could perhaps be confused with P. obovata and P. morrisonicola but these both have those leaves borne above the shoot depressed along it and those at the side depressed beneath it, while P. obovata has rather grey, often hairy shoots, and P. morrisonicola has much finer shoots and leaves (Mitchell 1972; Rushforth 1987).

Recent phylogenetic studies agree that Picea wilsonii belongs to what is generally treated as the third major clade of spruces, containing predominantly Asian species that are neither Japanese nor quadrangular-leaved (e.g. P. asperata and relatives), but beyond this there is no consensus as to its position (Ran, Wei & Wang 2006; Lockwood et al. 2013; Sullivan et al. 2017; Shao et al. 2019).