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Grimshaw, J.M., 'Taiwania cryptomerioides' from the website Trees and Shrubs Online (treesandshrubsonline.
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Large tree, to 60–70 (–80) m in maturity, with distinctly dimorphic growth phases. Juvenile phase persists until tree is c. 15 m (or perhaps more in cultivation), characterized by dense branching from the straight trunk; bark reddish-brown; the branches spreading to pendulous, with more or less pendulous branchlets, forming a densely clad conical or pyramidal tree; juvenile foliage ‘cryptomerioid’ with the leaves alternate to helically arranged, falcate-subulate (curved and needle-like, though the degree of curvature varies somewhat), with a broader base, 10–24 × 1.5–3.5 mm, bilaterally flattened, with a ridge on both sides, sharply pointed, glaucous-green in colour with glaucous wax on the surface, gradually transitioning in morphology to mature foliage. In maturity the tree is massive, with a long bare trunk and a broad, but sometimes ragged crown. Trunk straight and columnar above a slightly buttressed base, to 3–4 m in diameter, free of branches for up to 2/3 its length; bark thin, reddish-brown or brown, weathering to grey, peeling in thin strips or as flakes, eventually becoming fissured; branches becoming very large with age, more or less horizontal, creating a domed or flat crown; branchlets not pendulous, covered in appressed scale leaves; these ‘sequoiadendroid’ leaves scale-like, short and stout, appressed to or standing ‘free’ from the shoot, pointed with a broad base, curving to the tip, 3–6 × 1.2–3 mm, shiny dark green with whitish stomata and pale midrib; pollen cones in clusters of 2–7 at the ends of leafy shoots, rounded, 2–3 mm long, yellowish green, with numerous microsporophylls; seed cones solitary at the tips of branchlets, the scale leaves transitioning into cone scales, light green and 4–5 mm long when young, developing and maturing in one season to more or less cylindrical light brown cones, which mature in early winter, 12–20 × 6–11 mm, usually with 12–25 scales; seeds light brown, 14–30 per cone, flat, ovate-oblong, 4 × 2–3 mm, surrounded by a narrow (1–2 mm) wing; cotyledons 2 (–3). 2n = 22. (Luu & Thomas 2004; Farjon 2005).
Distribution Myanmar China Yunnan, Xizang (? naturalised Fujian, Guizhou, Hubei, Sichuan) Vietnam Taiwan
Habitat Coniferous or mixed forests, 1800–2600 m
USDA Hardiness Zone 7
RHS Hardiness Rating H5
Conservation status Vulnerable (VU)
Taxonomic note The name Taiwania flousiana Gaussen was given in 1939 to material from Yunnan collected by Handel-Mazzetti in 1916, based on small distinctions but Farjon (2005) has concluded that there are no consistent morphological characters to distinguish one population from another, though there are some genetic differences (Chou et al. 2008, Li et al. 2008). The name T. flousiana is persistent, however, and is used by both Western horticulturists and Chinese foresters for material of Chinese origin, who perceive differences in living plants, which may seem to be less glaucous than trees from Taiwan.
Named in 1906, Taiwania commemorates the island to which it was then thought to be endemic, while cryptomerioides acknowledges the similarity of at least the juvenile growth form to that of Cryptomeria japonica. Rather than being an island endemic, however, Taiwania is now known to occur in three centres of indubitable natural occurrence in Taiwan, Vietnam and the China/Myanmar border areas, all regions of high diversity and apparent refugia during glacial periods. Populations elsewhere may be naturalised. In the wild it can become huge and craggy and is one of the world’s great trees, achieving ages of 1600–2000 years (Fu et al. 1999, Farjon 2005). Its fine durable timber is sought-after in China for coffins (Kermode 1939, Kingdon Ward 1960), and the species has been very heavily exploited. It is now grown in plantations in both China and Taiwan.
Taiwania is now widely cultivated and has been introduced many times (see Grimshaw 2011 for an exhausting review), starting with four young plants brought back the USA from Taiwan in 1918 by Ernest Wilson. Many early trees were derived from cuttings taken from these plants, but a successful importation of seed from Taiwan was made in 1924 from which seedlings were distributed worldwide (Briggs 1993). The British Champion, planted in 1928 at Killerton, Devon, must derive from one of these introductions. It was 17 m in 2001 (Johnson 2003, TROBI 2011), while another early specimen at Garinish Island (21.5 m, 59 cm dbh, 2002) is regarded as the British and Irish Champion. Many of the early plantings did not flourish, whether from being grown from cuttings, or because of the prevailing climatic conditions; more recent introductions have typically made much more handsome specimens.
Most cultivated trees are derived from Taiwanese stock, whether through commercial, official or expedition sources, and such trees are often somewhat glaucous. Specimens with reliable provenance from the Chinese mainland are much harder to find, though the name T. flousiana occurs on labels and in print. They often lack glaucescence, appearing uniformly green. The first Chinese seed to reach the West was collected on the famous Metasequoia expedition of 1948 and it seems that seedlings were distributed in the 1950s. It is probable that most trees labelled T. flousiana derive from this collection (e.g. at the Hillier Gardens, 11.7 m (28 cm dbh) in 2009 (TROBI 2011), though there have been a handful of later introductions.
Experience has shown that Taiwania is much hardier in northern Europe than often thought, but it does help if the first few winters are kind to it, and it should be planted in a sunny site that has shelter ‘at its back’. Warm summers with ample moisture are preferred – growth of up to 3 m per year has been recorded in Georgia, but even in much cooler areas growth is relatively fast – 10 m in 15–20 years seems to be quite commonly achieved in northern Europe. The tallest cultivated trees in southern Europe, the USA, Australia and New Zealand have achieved 20 m or more (see Grimshaw 2011). It thrives in the south-eastern USA – Zone 7 and above, and also on the west coast. A memorably attractive specimen grows in the garden at Bishop’s Close, Portland, Oregon, and has a perfect shape, with layers of overlapping branches to the ground, their upturned tips giving it great elegance. It was planted in about 1980 (S. Hogan, pers. comm. 2011).
Seed is by far the best option for propagating Taiwania, giving vigorous, straight-growing trees with robust roots. Sown in warmth in spring germination occurs in 3–4 weeks, and growth is rapid. Young seedlings should be protected from hot sun, and if grown in cold climates given protection from frost for the first few years. Cuttings can be tried, but they root poorly and slowly, giving a 24–46% success rate over a period of 150–300 days for Fordham & Spraker (1977), with or without rooting hormone. There is a tendency to form sprawling plagiotrophic (i.e. non-vertical) growth but there is a view that if cutting-grown specimens are placed in shade they form upright shoots and grow normally.
A recurrent problem is the loss of the leader. Bizarre though it may seem, given the sharpness of the needles, slugs and snails are very fond of the new growth and often chew it down. Frost can also kill the leader, especially early in the winter when the autumnal growth flush has yet to harden. Philip Thomas (pers. comm. 2011) has observed that there are two distinct growth phases in the UK – one in May/June and another in October/November and it is at these times that it is most susceptible to both frost and mollusc damage. Between December and March even young shoots can tolerate –15oC if the growth is sufficiently hardened off (P. Thomas, pers. comm. 2011). Trees with damaged tips usually reform a leader and recover, but it can take some years before apical dominance is restored.
At present, most cultivated trees are still in the juvenile ‘cryptomerioid’ phase as the mature ‘sequoiadendroid’ phase has as yet seldom been attained. A healthy, vigorous young Taiwania is an attractive sight, with the pendulous growth forming swags of shoots falling from the pendulous branches to form a beautiful, if vicious, jade curtain. It is not a tree for caressing. When doing well it forms a shapely narrow spire, but some of the older specimens in the British Isles that were damaged by frost in their youth are gaunt and misshapen with little to commend them as ornamentals. Unless the lower branches are deliberately removed they are retained for many years, forming a skirt to the ground (T. Christian, pers. comm. 2011), though with age the stems become clean of branches to a great height. The leaves do reduce in size with age, however, changing from the long, green needles of the seedling and first few years of growth to stouter more curved structures that are less sharp and more glaucous.