ARAUCARIA araucana (Chilean pine) is sufficiently long-lived as a species to be classified as a ‘living fossil’. Paradoxically, it is now classified as endangered (since 2013) by the IUCN (International Union for Conservation of Nature) due to pressures from logging, forest fires and the overgrazing of seedling trees. We know the tree as a popular exotic addition to UK parkland and gardens, commonly called ‘monkey puzzle’. However, given the razor-sharp edges of the scale-like leaves, I doubt whether any wise old monkey (brass or otherwise) would dare swing on its branches.

Its natural habitat is the lower slopes of the south-central Andes in Chile and Argentina, typically above 1,000 m, favouring well-drained, slightly acidic volcanic soils. However, most soils are tolerated if they drain adequately, perhaps explaining why trees planted in Hyde Park grow so well. Araucaria araucana is the hardiest Araucaria species and the national tree of Chile.

Until banned in 1990, logging was a major threat, but forest fires continue to take their toll with thousands of hectares of Araucaria forest destroyed from 2001–2002. National parks have suffered significant losses, with trees over 1,300 years old destroyed. Overgrazing and invasive tree species are additional threats, together with human harvesting of the edible piñones (Araucaria seeds), thus preventing regeneration of natural Araucaria forest. A measure of this multi-factor threat is seen in a Global Trees Campaign project where 90 per cent of the 2,000 trees planted survived for 10 years or less.

Araucaria araucana is an evergreen conifer reaching 30 to 40 m in canopy height with a 1 to 1.5 m DBH (diameter at breast height). Bark is very thick and fire-resistant, a characteristic thought to have evolved in response to the historical frequency of forest fires in the tree’s natural Andean habitat. 
Young trees display a broadly pyramidal or conical-shaped canopy, developing with age into the distinctive umbrella form of mature trees. The rounded, triangular leaves are leathery and spiky with sharp edges and spiny tips, measuring 3 to 4 cm in length and 1 to 3 cm broad at the base. They have an extraordinarily long life span, with an average longevity close to a quarter of a century. As such, they form a spirally arranged scale-like covering over all except the older branches. Individual tree longevity can easily exceed one thousand years. 

Trees are normally dioecious (male and female reproductive structures borne on separate trees) but occasionally carry cones of both sexes. Male (pollen) cones are oblong and cucumber-shaped, 4 cm long at first, subsequently enlarging to 8 to 12 cm long and 5 to 6 cm wide at pollen release. The species is wind pollinated. Female (seed) cones mature in autumn about 18 months after pollination into large globose structures, 12 to 20 cm in diameter, containing around 200 seeds. At maturity, female cones disintegrate to release long nut-like seeds (3 to 4 cm long).

Araucaria araucana is a ‘masting’ or ‘mast seeding’ species. This means plants produce a surfeit of seeds every two or more years in regional synchrony with other individuals of the same species, a form of seeding common among conifer species growing in colder forests. Animals take advantage of surplus seeds, which they bury as a food reserve for leaner years. In reality, most seed stays in the ground to regenerate groves of young trees.

In this respect, rodents are important consumers and disseminators of Araucaria araucana seed. The long-haired grass mouse, Abrothrix longipilis, is the most important animal responsible for dispersing seeds of A. araucana in its natural South American habitat – especially since this particular rodent tends to bury seeds whole and in soils invariably suitable for subsequent germination. Seeds borne by trees growing in the UK are eaten and disseminated by squirrels and jays.

Araucaria araucana has become popular around the world as a landscape, amenity and garden tree, planted primarily for the peculiar effect of its reptilian branches and the symmetrical appearance of the tree as a whole. This is a tree of temperate climes responding well to high rainfall and tolerating extremely low temperatures, down to about −20 °C. There are other members of the Araucaria genus, and also southern hemisphere natives, but this one is by far the hardiest. Trees grow well in north-western Europe as far north as the Faroe Islands and Smøla in western Norway. Similarly, on the west coast of North America, as far north as the islands of Haida Gwaii in Canada. Trees are tolerant of coastal salt sprays but cannot cope with traffic or industrial pollution.
The tree’s piñones are edible, similar in size and shape to large pine nuts. They have been gathered over many millennia by indigenous peoples in Argentina and Chile. Araucaria araucana is thought to have some potential as a food crop for the future, particularly in climates with cool oceanic summers (such as western Scotland) where this tree thrives but mainstream nut crops do not. A group of six female trees with one male for pollination is calculated to yield many thousands of seeds per annum, and since seeds fall naturally, collection is relatively easy. However, one downside is that trees do not produce seeds until they reach 30 to 40 years of age. This clearly makes commercial planting an extraordinarily long-term proposition, perhaps discouraging investment in orchard planting. That said, seed yields (when they arrive) are massive, with established trees able to yield for 1,000 years or more.

Monkey puzzle was always highly valued as a source of timber due to its long, straight trunk and knot-free wood, but current rarity and vulnerable status (within its native range and habitat) means the wood is not so commonly used. Heartwood is light brown, sometimes with a yellow or red hue, with the lighter-coloured sapwood not well defined. Grain is usually straight, with a fine to medium uniform texture and a moderate natural lustre. The transition from earlywood to latewood is gradual, with low colour contrast. Tracheid diameter is medium to large. The timber is rated as non-durable to perishable with poor insect resistance, and also susceptible to fungal staining. Dried wood weighs in at 545 kg/m³.

The timber was first used to make railway sleepers for access into the coal fields, steel works, paper mills and ceramics industries growing up around the port of Concepción in the industrial heart of Chile. Later on, the timber was used for general carpentry, ladders, skis, piano interiors, oars, rulers and even aeroplanes. Before the tree became protected by law in the 1970s, sawmills in the Araucanía region of Chile specialised in this timber.

Araucaria araucana is currently listed in the CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) Appendix I as an endangered species and remains sacred to the Native South American Mapuche tribe. Whitby Jet (lignite), which is used to make jewellery, is derived from fossilised Araucaria araucana.

The Woodland Trust says “Araucaria araucana is unlikely to be confused with anything else”, but that’s not my experience. There are other members of the Araucaria genus, all natives of the southern hemisphere, including Araucaria bidwillii (bunya pine), a native of south-east Queensland in Australia but now planted across the country. My first sighting of this tree on Beaumont Common, on the outskirts of Adelaide, was sufficiently confusing to make me think I had come across a monkey puzzle tree a long way from its native home.

So how did the popular English name ‘monkey puzzle’ come about? Apparently, its roots can be traced back to the early cultivation of the tree in Britain around 1850, when the species was still a rarity in parks and gardens. Sir William Molesworth, proud owner of a young specimen at Pencarrow Garden near Bodmin in Cornwall, was showing it off to a group of friends when one of them is claimed to have said: “It would puzzle a monkey to climb that.” Because the species did not yet possess a common ‘tag’, the name ‘monkey puzzler’, and subsequently ‘monkey puzzle’, became universally accepted.