Pseudotsuga sinensis Dode

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Credits

Tom Christian & Aljos Farjon (2023)

Recommended citation
Christian, T. & Farjon, A. (2023), 'Pseudotsuga sinensis' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/pseudotsuga/pseudotsuga-sinensis/). Accessed 2024-03-28.

Glossary

Tibet
Traditional English name for the formerly independent state known to its people as Bod now the Tibet (Xizang) Autonomous Region of the People’s Republic of China. The name Xizang is used in lists of Chinese provinces.
asl
Above sea-level.
dbh
Diameter (of trunk) at breast height. Breast height is defined as 4.5 feet (1.37 m) above the ground.
karst
Landscape area formed by the dissolution of limestone by water with much exposed rock. Karst areas are usually rather arid due to the free-draining conditions.
mesophytic
(of a plant) Growing in moist (mesic) habitats.
taxon
(pl. taxa) Group of organisms sharing the same taxonomic rank (family genus species infraspecific variety).

Credits

Tom Christian & Aljos Farjon (2023)

Recommended citation
Christian, T. & Farjon, A. (2023), 'Pseudotsuga sinensis' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/pseudotsuga/pseudotsuga-sinensis/). Accessed 2024-03-28.

Monoecious evergreen coniferous trees to 50 m tall, dbh to 2 m; trunk more or less straight, columnar, or forked. Bark on trunk rough and very scaly, longitudinally fissured below, grey. Branches spreading wide, nearly erect near the top, forming a domed or flat topped crown. Branchlets slender, reddish-brown in the first year, soon becoming grey, variably but usually minutely pubescent in the grooves, soon glabrous, with small, slightly elevated, circular or angular leaf scars. Vegetative buds ovoid or ovoid conical, 4–8 × 3–4.5 mm, not or only slightly resinous; bud scales triangular, acute, lustrous red-brown, deciduous in the second year. Leaves more or less remote, pectinate, (0.7–)2.5–4(–5) cm long, highly variable, (1–)1.5–2.1(–3) mm wide, slightly twisted or curved at base, linear, usually straight, longitudinally grooved above, flattened, emarginate or sometimes obtuse at apex; hypostomatic, stomata in two greenish white bands separated by a midrib on abaxial (= under) side; leaf colour dark green above. Pollen cones pendulous at maturity, 1–1.5 cm long, yellowish. Seed cones on 1–2.5 cm long peduncles, persisting some years but finally deciduous, ovoid to ovoid-oblong, (3.5–)4–6.5(–8) cm long, (2–)3.5–5(–5.5) cm wide with opened scales, purplish, maturing to purplish brown or brown. Seed scales rhombic-orbicular, suborbicular, or semi-orbicular to reniform, convex, usually apically slightly thickened and lignified, 2.5–3 × 3–3.5 cm at mid-cone, slightly puberulent at first, but soon glabrous; upper margin entire; base short pedicellate. Bracts ligulate-linear, with trilobate apex, cusp longer than lateral lobes, 3.5–4 cm long, exserted, recurved or reflexed. Seeds cuneate-ovoid, 8–12 × 5–8 mm, light brown with dark spots; seed wings ovate, 8–15 mm long, brown with dark spots. (Farjon 2017).

Distribution  China S Anhui, Fujian, SW Guangxi, Guizhou, W Hubei, N Hunan, N Jiangxi, S Shaanxi, Sichuan, SE Xizang [Tibet], Yunnan, Zhejiang Vietnam N Taiwan

Habitat Low to medium-high mountains at various elevations (600–3300 m asl, see individual accounts below), characterised by a temperate to warm-temperate and moist climate. It occurs everywhere as a minor component of mixed mesophytic forests dominated by broadleaves including evergreen broadleaves in some locations.

USDA Hardiness Zone 9

RHS Hardiness Rating H3

In contrast to North America, where Pseudotsuga menzesii occurs over a huge, near-continuous north-south range in the western part of that continent, Asian Pseudotsuga populations are widely scattered in the various mountain ranges that provide floristic stepping-stones between the eastern end of the Himalayan chain and mountainous areas of northern Vietnam, southern Japan and Taiwan. Nowhere within this vast distribution do they ever dominate the forest in the same way as the American giant (Farjon 2017; Debreczy & Rácz 2011).

The taxonomic positions of the Asian populations are probably the most contentious in the genus. Only the Japanese Pseudotsuga japonica, neatly ensconced on Honshu and Shikoku, enjoys universal acceptance, but numerous names have been described to cover the variation inherent in the remaining populations scattered across mainland Asia and Taiwan. The oldest validly published name for this group is Pseudotsuga sinensis, and in the most conservative treatments – including those of Aljos Farjon, a co-author of this work – all other populations are placed here, either at infraspecific rank or else in synonomy:

Farjon (1990, 2001, 2017) recognises two varieties: var. brevifolia and var. gaussenii; within the nominate var. sinensis he includes P. forrestii from Yunnan and P. wilsoniana from Taiwan;

Flora of China (Fu, Li & Mill 1999) recognises P. brevifolia and P. forrestii at species rank, sinks var. gaussenii into var. sinensis, and treats Taiwanese populations as P. sinensis var. wilsoniana which the authors acknowledge ‘is not markedly distinct morphologically’, and justify the separation principally by geographic isolation;

Debreczy & Rácz (2011) adopt the same position as Flora of China but continue to recognise var. gaussenii. These authors also concede that vars. gaussenii and wilsoniana are difficult to distinguish from var. sinensis, but maintain them anyway.

Here, we seek to balance horticultural interest with taxonomic reality by adopting Farjon’s ‘one species’ view but recognising four varieties rather than two: var. brevifolia (southern Guizhou to northern Vietnam), var. forrestii (Hengduan mounains in NW Yunnan and perhaps adjacent SW Sichan and SE Tibet), var. gaussenii (Zhejiang and perhaps adjacent areas), and var. wilsoniana (Taiwan). The type is, according to this compromise, scattered through southern Shaanxi, western Hubei, northwest Hunan, eastern Sichuan, northwest Guizhou and northeast Yunnan (Farjon 2017; Debreczy & Rácz 2011; Fu, Li & Mill 1999). More detailed discussion, where appropriate, may be found under the relevant articles below.

None of these entities is represented in cultivation by more than a scattering of specimens in specialist collections. Perhaps the most widespread are those originating from Taiwan, from where multiple introductions have been made since c. 1991, hence recognising var. wilsoniana enables us to discretely frame our discussion of these introductions, while recognising var. forrestii acknowledges the results of the recent phylogenetic study of Wei et al. (2010) which supports this taxon as a distinct entity. Var. gaussenii is probably not in cultivation but is discussed below for completeness.

In all its forms Pseudotsuga sinensis occurs in the temperate to warm-temperate climate zone in low to medium-high mountains at various elevations, from 600–1200 m in southeast China, 1000–2700 m in Taiwan, and up to 3300 m asl in western China (Farjon 2017). Quite unlike the North American species, it occurs in mixed mesophytic forests dominated by evergreen broadleaves, where conifers are usually a minor or scattered component. Consequently, the architecture of Asian Pseudotsuga is quite different, with trees developing spreading or even umbrella-shaped crowns, and none of them reach anything like the proportions of P. menziesii (Farjon 2017). 40–50 m is the oft-quoted maximum for most of these taxa in the wild, including P. japonica, while P. sinensis var. brevifolia matches its short leaves with short stature, reaching only 10 m on the karst limestone mountains of southern China and extreme northern Vietnam (Debreczy & Rácz 2011; Fu, Li & Mill 1999).

In gardens these trees are smaller still. The oldest extant plants – a pair of originals from Forrest 13003 (var. forrestii) at Werrington, Cornwall, UK – are c. 15 m × 45 cm dbh (TC pers. obs.); most are much smaller (Tree Register 2023). All these taxa enjoy good, deep, moist but well drained acid soils and plenty of shelter in areas with high precipitation, mild winters, and warm summers. When raised from seed, as so many recent introductions from Taiwan have been, plants tend to spend many years in a shrubby phase, becoming large bushes from which a central leader eventually emerges after several to many years (Grimshaw & Bayton 2009). Grafted plants can be more vigorous and arborescent from a young age, but are difficult to produce and to grow on well (K. Rushforth pers. comm. 2023).


var. brevifolia (W.C.Cheng & L.K.Fu) Farjon & Silba

Common Names
短叶黄杉 (duan ye huang shan)
Short-leaf Douglas Fir
Thiêt Sam Gia

Synonyms
Pseudotsuga brevifolia W.C.Cheng & L.K.Fu

Tree to 10 m × 0.6 m dbh, bole short, crown rounded to umbrella shaped in mature trees, first order branches curving strongly upward. Branchlets densely pubescent at first, turning glabrous or subglabrous in 2nd or 3rd year. Leaves 0.7–1.5(–2) cm long, 2–3(–3.2) mm wide. Buds ovoid, obtuse, 4–5 × 3 mm. Seed cones 3.7–6.5 cm long, 3–4 cm wide when opened. Seed scales compressed, suborbicular to rhombic-orbicular. Bracts about as long as seed scales. (Farjon 2017; Debreczy & Rácz 2011; Fu, Li & Mill 1999).

Distribution

  • China – SW Guangxi (Daxin, Jingxi, Lingyun, Leyi, Longzhou, Napo), Guizhou (Anlong, Lipuo)
  • Vietnam – Extreme north, in Cao Bang, Ha Giang, Lang Son

With its short, relatively wide needles, Pseudotsuga sinensis var. brevifolia is one of the more distinctive of the Asian Douglas Firs. This isn’t as helpful as it might seem, as it is barely in cultivation; the only plant traced during research for this account is one raised from TH 3564, collected in north Vietnam and growing at Tregrehan, Cornwall, UK. In 2023 this was c. 2 m tall (T. Hudson pers. comm. 2023). Keith Rushforth had previously introduced it from northern Vietnam but the only resulting plant, in Rushforth’s own Devon arboretum, has since died (K. Rushforth pers. comm. 2023).


var. forrestii (Craib) Silba

Common Names
澜沧黄杉 (lan cang huang shan)
Yunnan Douglas Fir
Forrest Douglas Fir

Synonyms
Pseudotsuga forrestii Craib

Tree to 40 m × 0.8 m dbh, bole long, crown broad-conical in mature trees, first order branches upswept at first, later spreading more or less horizontally, upswept near their ends. Branchlets glabrous or subglabrous. Leaves 2.8–5.5 cm long, 1.3–1.8(–2) mm wide, margins slightly revolute. Seed cones 5–8 cm long, 4–5.5 cm wide when opened. Seed scales compressed, suborbicular to rhombic-orbicular. Bracts obviously longer than seed scales. (Debreczy & Rácz 2011; Fu, Li & Mill 1999).

Distribution

  • China – Hengduan mountains in NW Yunnan, and perhaps adjacent regions of SW Sichuan and SE Xizang (Tibet)

RHS Hardiness Rating: H3

USDA Hardiness Zone: 9

A pair of original trees from Forrest 13003, gathered in the Mekong Valley in August 1914, persist at Werrington, Cornwall, UK. The better of the two is c. 15 m × 45 cm dbh (TC pers. obs.) Both trees appear quite chlorotic and when seen for the first time one is conditioned, in this period of unprecedented plant health concerns, to jump to pessimistic conclusions (TC pers. obs.) but Keith Rushforth, who has known these trees for over thirty years, asserts that they have always looked this way. Rushforth has propagated both at various intervals and a few grafts have been distributed to specialist collections including White House Farm (Kent, UK). Grafts of Asian Pseudotsuga are difficult to grow on but those that have survived usually look healthier than their progenitors.

Additional material has been introduced under Cox 6504; trees from this introduction grow at Benmore and Westonbirt and Keith Rushforth has propagated both these trees in recent years (K. Rushforth pers. comm.). An original tree from this introduction grows in the Den at Glendoick and was 4.5 m × 11 cm dbh in 2017 (Tree Register 2023).


var. gaussenii (Flous) Silba

Common Names

Synonyms
Pseudotsuga gaussenii Flous

Leaves 1.6–3 cm long, 1.7–2 mm wide, distinctly parallel sided, chalk-white below, the midrib often obscured by stomata in the first year. Buds ovoid-conical, more or less acute, 4–5 × 3 mm. Seed cones 3.5–5.5 cm long, 2–3.5 cm wide when opened; seed scales broad flabellate to reniform. Bracts slightly longer than seed scales, upswept. (Farjon 2017; Debreczy & Rácz 2011).

Distribution

  • China – Fujian (Jianning), Jingxi (Dexing), Zhejiang

Described from Zhejiang in 1936, var. gaussenii is an unusual case in that the Flora of China authors (Fu, Li & Mill 1999) sink it into var. sinensis, while others, notably Farjon (1990, 2001, 2017) and Debreczy & Rácz (2011) maintain it as distinct. The area where it was originally found - and additional areas where it has been located since – have all suffered dramatic deforestation; uncertainties about its past distribution and abundance make it difficult to characterise. It is not known to be in cultivation, but is included here for completeness. According to Debreczy & Rácz (2011) it may be easily distinguished from the other varieties by the chalk white undersides to the leaves, at least partially obscuring the midrib.


var. sinensis

Synonyms
Pseudotsuga xichangensis C.T. Kuan & L.J. Zhou
Pseudotsuga shaanxiensis S.Z. QU & K.Y. Wang

Leaves 1.3–4 cm long, 1.5–2 cm wide. Buds ovoid-conical, more or less acute, 4–7 × 3–4 mm. Seed cones 4.5–8 cm long, 3–5 cm wide when opened. Seed scales suborbicular to rhombic-orbicular. (Farjon 2017).

Distribution

  • China – S Anhui (?), Chongqing (?), Fujian (?), NW Guizhou, W Hubei, N Hunan, N Jiangxi, S Shaanxi, NE Yunnan, Zhejiang
  • Vietnam – N

RHS Hardiness Rating: H3

Described by the French botanist Luis-Albert Dode in 1912, Pseudotsuga sinensis is the oldest name for any of the taxa distributed in mainland Asia and Taiwan. In 1989, in the absence of a specified holotype, Farjon lectotypified a specimen collected by the French missionary and plant collector Édouard-Ernest Maire in Yunnan in 1911 (s.n.) previously determined by Dode and presumably intended as a type in the original publication. Maire’s un-numbered 1911 specimen is deposited at Paris, along with three others collected by Maire with fellow Frenchman François Ducloux in 1909 (Ducloux 6570).

According to an unattributed notice in The Gardeners’ Chronicle of June 15, 1912 (Ser. 3, v. 51, p. 396) Ducloux had dispatched seed to Dode, but it isn’t clear when, nor indeed whether multiple seed collections arrived in quick succession. Regardless, Dode sent at least a proportion of this seed to the Orleans firm Chenault et Fils, who raised plants and were soon supplying young trees to multiple collections in Europe and North America, for example to the Arnold Arboretum in 1914 (Arnold Arboretum 2023). No original trees are known to survive, but several have been grafted over the years, and there are plants at the Sir Harold Hillier Gardens descended from the Chenault stock.

Other UK examples grow at Bedgebury National Pinetum, Kent, and at Tregrehan, Cornwall. The Tregrehan tree was raised from TH 910 – seed gathered from a fragment of native vegetation surviving within the precinct of a temple c. 60 km west of Kunming. Now some 20 years old, this tree is c. 6 m tall (T. Hudson pers. comm. 2023).


var. wilsoniana (Hayata) L. K. Fu & Nan Li

Common Names
Taiwan Douglas Fir
台湾黄杉 (tai wan huang shan)

Synonyms
Pseudotsuga wilsoniana Hayata

Tree to 30 m × 2 m dbh. Leaves 1.5–2.5(–4.5) cm long, 1–1.5 mm wide. Seed cones 4.5–6 cm long, ovoid. Seed scales kidney-shaped to roundly wedge-shaped, 1.5–2 cm. (Debreczy & Rácz 2011; Eckenwalder 2009).

Distribution

  • Taiwan – Xueshan and Central Mountains

Taxonomic note For a while the Pseudotsuga populations on Taiwan were treated as a distinct species, P. wilsoniana Hayata, but for some time now they have been accepted as falling within the diversity of P. sinensis. Some authors sink it entirely while others choose to maintain it at the rank of variety. In their account for Flora of China Fu, Li & Mill (1999) admit the justification is weak and that (when recognised) P. wilsoniana is difficult to distinguish from P. sinensis. P. wilsoniana was described by the Japanese botanist Bunzo Hayata in 1915, while P. sinensis was described by the French botanist Luis-Albert Dode in 1912. Hayata did not mention Dode’s species from mainland China, which given the political situation in 1914–15 should not come as a surprise. Geographical separation on Taiwan is well known for other tree species, perhaps most famously Taiwania cryptomerioides which occurs in three widely separated populations, in Taiwan, Yunnan and in northern Vietnam. Named after the famous botanical explorer E.H. Wilson, who also introduced P. wilsoniana to cultivation, it is no coincidence that Hayata’s name was taken up in anglophone horticulture rather than that of the Frenchman Dode. If we consider them synonymous, P. sinensis has priority over P. wilsoniana. The morphological characters overlap, perhaps with somewhat narrower leaves and smaller seed cones similar to P. japonica. We give this taxon the benefit of the doubt here. AF.

Taiwan has been the source of most recent introductions of Pseudotsuga sinensis s.l. to western collections, notably those of the Edinburgh Taiwan Expedition of 1993 (ETE 112, 149, 150, 157, 162, 177) and collections by Kew (ETOT 7, 61) (Grimshaw & Bayton 2009). Additionally, the Taiwan Forest Research Insitute (TFRI) has distributed seed lots via Index Seminum since at least the mid 1980s. Like other P. sinensis taxa it requires warmth, rainfall and humidity to thrive, and on that basis has been among the most disappointing of the many introductions of Taiwanese conifers made in recent decades, but some individuals in favourable sites are beginning to make good trees.

Among the best in the UK is a tree at Sir Harold Hillier Gardens, Hampshire. Collected in Taiwan and accessioned in 1982 it was 9.7 m × 17 cm dbh in 2017, with a canopy spread of 8.1 m by 2011; another, raised from TFRI seed at Edinburgh and dispatched to Foxhill Arboretum, Cheshire, by the International Conifer Conservation Programme was 9 m × 25 cm dbh in 2023; a tree from ETE 149 at Picton Castle, Pembrokeshire, where a great diversity of Taiwanese conifers were sent from Edinburgh in the mid 1990s, was 7 m × 19 cm in 2018; while a plant from ETOT 7 at Kew was a comparatively disappointing 2.5 m × 23 cm dbh in 2022 (Tree Register 2023). ETOT 61 is also cultivated on the west coast of North America, at the UBC Botanical Garden in Vancouver (University of British Columbia 2023). Material has been tested several times at the Arnold Arboretum but has never survived for very long, probably due to the harshness of the winters there; the latest attempt, with TFRI seed received in 2017, includes a few survivors in 2023 (Arnold Arboretum 2023). Young trees are also growing at Arboretum Wespelaar, Belgium, where the best, from H&M 2461, gathered at 1625 m asl, was c. 5 m × 10 cm dbh in October 2022 (acc. 14314; TC pers. obs.).