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Tree to 40 m, trunk to 1.2 m dbh. Bark reddish brown, peeling in small, thin scales; in mature plants, bark deep, soft and spongy, with distinctive nodules to 1.5 cm long. Crown slender and columnar, but trees often branch from the base. Shoots terminated by a resting bud that is usually covered by a heavy white resinous secretion, sometimes called the ‘polar cap’. Major branches rather short, arching upwards or horizontal. Branches composed of distinctive repetitive growth units, in which the leaves are initially small and scale-like, gradually increasing in length; these units giving the stems a modular appearance. Juvenile leaves distichous, dark green above and glaucous below, 0.3–8 × 0.2–0.5 cm, linear to narrowly triangular, apex obtuse. Adult leaves in four rows, decurrent, leathery, dull light green to dark green, 0.3–4 × 0.4–0.8 cm, no distinct midrib, apex rounded. Male strobili terminal on first-order leafy shoots, 10 × 2 cm, microsporophylls numerous (over 500 per strobilus), dark reddish brown. Female cones terminal on first-order leafy shoots, often on branches above those bearing male strobili; cones sessile, globular to ellipsoid, 12.5 × 10 cm, green, turning brown later, shedding bract scales. Bract-scale complexes are formed, from fusion of the seed scales and the bracts, such that the component parts are indistinguishable. These complexes are numerous (over 300 per cone), flattened, roughly rhombic, 1.2–1.7 × 1.4–2.2 cm, with a conspicuous recurved point, each bearing one seed. Seeds pale brown, rectangular to cuneate, 0.7–1.1 × 0.5–0.7 cm including a narrow, circumferential wing. Jones et al. 1995. Distribution AUSTRALIA: New South Wales (Wollemi National Park). Habitat Known from a single almost inaccessible sandstone gorge system in the Blue Mountains, where the trees grow in acidic soils alongside a permanent stream. USDA Hardiness Zone 8–9. Conservation status Critically Endangered. Fewer than 100 mature trees of Wollemia are known to exist in the wild, and their genetic diversity is extremely low. They are threatened by fire, poor regeneration, competition with other trees, and pathogens. Illustration Jones et al. 1995, Farjon 2001, Pastoriza-Piñol 2007, and many others; NTxi, NT20, NT898, NT900. Taxonomic note The taxonomic affinities of Wollemia are relatively unambiguous; the broad leaves with no central midrib and the large female cones with fully fused bract-scale complexes clearly place these plants in the Araucariaceae. Unique features of Wollemia are the bark (sometimes likened to bubbling molten chocolate), and the terminal placement of the male strobili and female cones. Phylogenetic studies of the Araucariaceae suggest that Wollemia is sister to Agathis (Gilmore & Hill 1997).
Perhaps no other tree has generated such a frenzy of hype as Wollemia nobilis, whose Lazarus-like career has brought it straight from the age of the dinosaurs to the age of celebrity. Newspaper and magazine articles galore, scientific journals and a book (Woodford 2000) have covered it on paper, and at the time of writing it featured on ‘about’ 54,800 websites (according to Google, June 2008 – though for comparison, it should be noted, Quercus robur generated 1,030,000 hits!), including ‘the official home of the Wollemi Pine’ (www.wollemipine.com) (Wollemi Pine 2004–2008). A particularly useful website, however, is that provided by the Botanic Gardens Trust, Sydney, Australia (Botanic Gardens Trust 2008), and the very informative Wollemi Pine Recovery Plan (see below) is also available online (New South Wales Department of Environment and Conservation 2006). These and the accounts by Jones et al. (1995) and Pastoriza-Piñol (2007) have provided the basis of the following discussion.
The tale of the plant’s discovery in 1994 by the adventurous David Noble of the New South Wales National Parks and Wildlife Service has been frequently recounted, and need only be briefly recapitulated here. While exploring a gorge in the Wollemi Wilderness – a particularly remote and rugged tract of the Wollemi National Park (which appropriately derives its name from an Aboriginal word meaning ‘look around’ or ‘watch your step’) – Noble came across a small group of trees that he did not recognise and collected a fragment for identification. Further specimens were collected, the species was quickly described and information about it was released, triggering intense interest worldwide. Not the least extraordinary part of the story was that this tree, promptly if inaccurately dubbed the ‘Wollemi Pine’, was growing within 200 km of Sydney.
There were not very many specimens, however, and even after the location of another group in 1994 and a third in 2000, all within 2–3 km of each other in the same canyon system, there are still fewer than 100 adult individuals known in the wild, plus 200–300 juveniles. The largest tree (known as King Billy) is 40 m high, and estimated to be over 1000 years old, but the range of size classes in the population suggests some recruitment from seed. They also regenerate vegetatively, from meristems below the bark, and are capable of coppicing. The ultimate potential size for the species is unknown. Their native habitat is warm temperate rainforest in the bottom of the gorge, where there is a small stream.
Owing to the extreme rarity and interest of the trees, access to the gorge where they occur is very strictly controlled and its location is kept secret, not only for fear of damage by human intruders but also to prevent contamination by alien fungi and parasites. A programme for management of the species, the Wollemi Pine Recovery Plan, is being implemented by the New South Wales Government Department of Environment and Climate Change (New South Wales Department of Environment and Conservation 2006). Not long after its discovery, the New South Wales National Parks and Wildlife Service, together with the Royal Botanic Gardens, Sydney, took the decision to propagate and distribute Wollemia commercially under licence, nationally and internationally, as a method of safeguarding its future survival. This innovative process provides collectors and horticulturists with a much sought-after tree while also raising funds for conservation of wild Wollemia and other threatened Australian plants. Much of the financing of the Recovery Plan (estimated at up to AUS $1,336,000) is expected to be derived from this income.
Seed and propagating material were collected on early visits to the site, and the first tree to be publicly unveiled was planted in the Royal Botanic Gardens, Sydney in 1998. Seedlings were presented to Kew in 1997, and there was a specimen growing happily (unlabelled) in the Temperate House well in advance of its ‘first planting’ there by Sir David Attenborough in 2005, outside the Orangery. The contract for the commercialisation of Wollemia was awarded to the Queensland Forestry Institute and Birkdale Nursery in 1999, and later that year they received 500 plants from the Royal Botanic Gardens, Sydney. From these, approximately half a million young plants have been produced, mostly as cuttings, and these in turn have been made available worldwide through selected nursery partners, starting in 2006 – at premium prices. A young Wollemia of approximately 50 cm in a three-litre pot cost £97 on first release in the United Kingdom (though the price in continental Europe was much cheaper, at €97!), and at the time of writing trees up to 180 cm tall were available in the United Kingdom for £1000 (Wollemi Pine 2004–2008).
These small individuals generally available represent the second wave of the introduction, however, which started with an auction of the ‘Wollemi Pine Collectors Edition’, comprising almost 300 plants grown by the Royal Botanic Gardens, Sydney from cuttings of known, named parent trees in the gorge. The auction was conducted by Sothebys in October 2005, in the gardens, and achieved the expected press coverage. Bidding was brisk and the second lot, of two specimens propagated from the Bill Tree and the de Carvalho Tree, was acquired for Worcester College, Oxford via an early-morning telephone bid (E. Wilson, pers. comm. 2006). Now planted permanently in the college grounds, these two trees are among the very select group of ‘originals’ in Britain. Another auctioned specimen reached Tregothnan, Cornwall, where in 2008 it became the first plant outside Australia known to have produced female cones (Tregothnan 2008); specimens at Kew had earlier produced male cones (T. Kirkham, pers. comm. 2008). Import regulations prevented American collectors from taking part in the auction, and the first commercial plants were released there in 2007, though it had been growing in a few arboreta prior to this (S. Hogan, pers. comm. 2008).
The introduction of Wollemia is in many ways reminiscent of those celebrated conifer introductions in the 1840s and ’50s, of Sequoia and Sequoiadendron, which also sold for celebrity prices, or that of Metasequoia in 1948. Whether Wollemia will perform so well, and stand to be recognised as the tree of the 2000s, remains to be seen. When work started on New Trees in 2004 there were no specimens growing outdoors in our area, and there was some discussion as to whether it should be on our list for inclusion. The first tree at Kew, planted near the Orangery in 2005 and enclosed in a cage for its protection, is now (in 2008) over 2 m tall, exceeding the top of the cage and threatening to escape at the sides. It has shown no evidence of any perturbation by winter weather, although temperatures have not fallen below –5ºC. Others have now been planted, in large numbers it seems, in gardens and collections throughout western Europe, and the story seems to be that they are surviving winters well both in Europe and in parts of eastern North America. At Plant Delights Nursery, Raleigh in North Carolina a specimen planted in February 2007 has withstood –10 ºC on numerous occasions over two winters, and has tolerated fierce summer temperatures over 40 ºC with equanimity. This individual is now one metre tall; a second, however, planted at the same time but in a drier situation, has grown much more slowly (T. Avent, pers. comm. 2008). In addition, in 2008 Tony Avent planted an allee of Wollemia at Juniper Level Botanic Garden, adjacent to Plant Delights Nursery. Plants are surviving as far north as Washington DC, although several have been lost at the US National Arboretum, perhaps because they were planted too late in the season and did not have time to become established (R. Olsen, pers. comm. 2008).
The apparent hardiness of Wollemia has come as a surprise to most gardeners – perhaps principally due to the stereotypical image of sunbaked Australia, rather than through rational analysis of its habitat. The Wollemi Pine Recovery Plan provides a chart of air temperatures for one year of monitoring at the primary site and demonstrates that mean winter temperatures there are somewhere around 5–7 ºC, with actual minima in the three midwinter months hovering around zero. Summer maxima are at around 30 ºC, with mean summer temperatures between 15 and 20 ºC (New South Wales Department of Environment and Conservation 2006). This is not very different to temperatures experienced in maritime western Europe. Beyond the current temperate climate in Wollemi National Park, and any ancestral hardiness ‘left over’ from earlier times, an important factor in its hardiness must be that it has a definite dormancy, the terminal bud shutting down when conditions are unsuitable for growth and being protected to some extent by the resinous exudate of the ‘polar cap’.
In production in Australia potted plants seem to require an acidic medium (less than pH 6), and in the wild the soil is pH 4.5. At Evenley Wood, Northamptonshire Tim Whiteley (pers. comm. 2008) has specimens growing on both acidic (pH 5.5) and alkaline (pH 8) soil, and reports no difference in vigour. The Worcester College specimens, however, are in soil of about pH 7–7.2 (planted out in 2006), and by early summer 2008 were looking decidedly unhappy, with poor growth and yellowish foliage. After treatment to reduce the pH they responded extremely quickly, re-greening and producing normal shoots within a couple of weeks (E. Wilson, pers. comm. 2008) – suggesting that any apparent tolerance of alkalinity may be shortlived. In general, plants of Wollemia respond well to fertilisers, and can grow surprisingly fast in cultivation. Yet another point of interest with this remarkable species is that it is the only member of the Araucariaceae to have two forms of mycorrhizal association, wild specimens having been found to have both arbuscular mycorrhizae and ectendomycorrhizae (Botanic Gardens Trust 2008). Cultivated specimens are often sold with a sachet of mycorrhizal inoculant, to be deployed on planting.
Other fungal associations are less happy. In cultivation Wollemia is susceptible to diseases caused by Botryosphaeria fungi, and to dieback or root rot from infection by the aggressive water-borne pathogen Phytophthora cinnamomi, common in Australia (as well as having a very broad range elsewhere), spores of which can be carried on shoes – which is one reason why access to the native trees is so carefully restricted. Unfortunately it seems that wild trees have already been infected, possibly via unauthorised visitors (New South Wales Department of Environment and Conservation 2006).
Its detractors may say that it looks like a fake Christmas tree made out of plastic seaweed (perhaps to be decorated with dinosaur models, as suggested by Tony Avent in the 2008 Plant Delights Nursery catalogue), but Wollemia nobilis is a remarkable tree with a potential that is as yet almost totally unexplored.