Wollemia nobilis

Wollemia nobilis is an evergreen tree reaching 25–40 m (82–131 ft) tall. The bark is very distinctive, dark brown, and knobbly, quoted as resembling the breakfast cereal Coco Pops. The tree coppices readily, and most specimens are multiple-trunked or appear as clumps of trunks thought to derive from old coppice growth, with some consisting of up to 100 stems of differing sizes. The branching is unusual in that most of the side branches never have further branching. After a few years, each branch either terminates in one or a succession of cones (either male or female) for up to about 12 years. New branches then arise from dormant buds on the main trunk. As trees mature, side branches often turn erect and develop into secondary trunks, which then bear new sets of side branches, resulting in the multi-trunked trees in the wild population. The leaves are flat linear, 3–8 cm (1.2–3.1 in) long and 2–5 mm (0.079–0.197 in) broad. They are arranged spirally on the shoot but twisted at the base to appear in two or four flattened ranks. As the leaves mature, they develop from bright lime-green to a more yellowish-green. The seed cones are green, 6–12 cm (2.4–4.7 in) long and 5–10 cm (2.0–3.9 in) in diameter, and mature about 18–20 months after wind pollination. They disintegrate at maturity to release the seeds which are small and brown, thin and papery with a wing around the edge to aid wind-dispersal. The male (pollen) cones are slender conic, 5–11 cm (2.0–4.3 in) long and 1–2 cm (0.39–0.79 in) broad and reddish-brown in colour and are lower on the tree than the seed cones. Cone bearing starts at a young age; the trees planted at Kew in 1997 produced their first cones in 2008, when 10–11 years old. Seedlings appear to be slow-growing and mature trees are extremely long-lived; some of the older individuals today are estimated to be between 500 and 1,000 years old.

==== Threats ==== In November 2005, wild-growing trees were found to be infected with Phytophthora cinnamomi. New South Wales park rangers believe the virulent water mould was introduced by unauthorised visitors to the site, the location of which is still undisclosed to the public. The grove of Wollemia trees was endangered by fire during the 2019–2020 Australian bushfire season. They were saved by specialist firefighters from the National Parks and Wildlife Service, supported by the Rural Fire Service who installed an irrigation system as well as dropping retardant.

The discovery, on or about 10 September 1994, by David Noble, Michael Casteleyn, and Tony Zimmerman, occurred only because the group had been systematically exploring the area, looking for new canyons. Noble had good botanical knowledge, and quickly recognised the trees as unusual because of the unique bark, and worthy of further investigation. He took specimens to work for identification, expecting someone to be able to identify the plants. His specimens were identified as new by Wyn Jones, a botanist with National Parks and Jan Allen from the Botanical Gardens. After the identification was made, National Parks then went under a veil of secrecy, with the discoverers not learning the full magnitude of their discovery for about six months. National Parks came close to damaging the stand when a helicopter used to collect cones inadvertently pruned one of the pines with its rotor. The species was subsequently named after David Noble. The first illustrations of the Wollemi Pine were drawn by David Mackay, a botanical artist and scientific illustrator who was working at the Royal Botanic Gardens in Sydney when the species was discovered. Further study would be needed to establish its relationship to other conifers. The initial suspicion was that it had certain characteristics of the 200 million year-old family Araucariaceae, but was not similar to any living species in the family. Comparison with living and fossilised Araucariaceae proved that it was a member of that family, and it has been placed into a new genus, beside the genera Agathis and Araucaria. Fewer than 60 adult trees are known to be growing wild in four locations, not far apart. It is very difficult to count individuals, as most trees are multi-stemmed and may have a connected root system. Genetic testing has revealed that all the specimens are genetically indistinguishable, suggesting that the species has been through a genetic bottleneck 10,000–26,000 years ago, in which its population became so low (possibly just one or two individuals) that all genetic variability was lost. A propagation programme made Wollemi pine specimens available to botanical gardens, first in Australia in 2006 and subsequently throughout the world. It may prove to be a valuable tree for ornament, either planted in open ground or for tubs and planters. In Australia, potted native Wollemi pines have been promoted as a Christmas tree. It is also proving to be more adaptable and cold-hardy than its restricted temperate-subtropical, humid distribution would suggest, tolerating temperatures between −5 and 45 °C (23 and 113 °F), with reports, from Japan and the United States, that it can survive down to −12 °C (10 °F). A grove of Wollemi pines planted in Inverewe Garden, Scotland, believed to be the most northerly location of any successful planting, have survived temperatures of −7 °C (19 °F), recorded in January 2010. It also handles both full sun and full shade. Like many other Australian trees, Wollemia is susceptible to the pathogenic water mould Phytophthora cinnamomi, so this may limit its potential as a timber tree. The Royal Botanic Gardens in Sydney has published information on how to grow Wollemi pines from seed harvested by helicopters from the forest trees. The majority of seeds that fall from the cone are not viable so need to be sorted to retain the plump and dark ones. These can then be sown on top of seed raising mix and watered. Once the water has drained through the mix, the pot should be placed in a plastic bag and refrigerated for two weeks. After this, the pot should be removed from the plastic bag and placed somewhere warm but not very sunny until the seed germinates (remembering to keep them moist but not wet). This could take several months.