Hoop Pines

Hoop Pines


Araucaria cunninghamii

Mudie 1829

pronounced: air-ah-KAIR-ee-uh kun-ning-HAM-ee-eye

(Araucariaceae — the bunya family)

common name: hoop pine

native 4Araucaria was named for the Araucarian Indians of Patagonia, who inhabited the region where the first Araucaria was discovered. Cunninghamii is for the great botanist and explorer Allan Cunningham (1791–1839). Cunningham visited Cleveland Bay (on which Magnetic Island is situated) on 14th-16th June, 1819, while serving as botanist on Mermaid, commanded by Captain Phillip Parker King. They anchored off Cape Cleveland to take on water, and Cunningham and King ventured on shore for an exploratory walk. Whenever Cunningham describes the hoop pine in his journal, he always refers to it as the "Norfolk Island pine", so it is rather ironic that the hoop pine was later named in his honour.

The hoop pine is a native of the eastern coast of Australia from Coffs Harbour in northern New South Wales up almost to Cooktown. A closely related variety occurs on the mountains of Papua-New Guinea and in parts of Indonesia. Some botanists claim the hoop pines that grow here to be a variety (or a form) found only on Magnetic Island, ssp. glauca. This seems to have been first suggested by Stephan Ladislaus Endlicher in 1847. Endlicher was a prominent Austrian botanist who published, among many other works, some of the early works on Australian flora, his information being mainly derived from specimens collected by Carl von Hugel. The main differences between our hoop pines and those growing on the mainland appear to be in the growth form, especially at the top of the tree.

The hoop pine was the foundation of the Australian plywood industry, and the existing population is a remnant, usually only still standing because the trees are in not-easily-accessible situations. It would seem (anecdotal evidence only) that the slopes of Melton Hill and Castle Hill in Townsville were originally well-timbered with hoop pine, but the trees were felled within a few years of European settlement, partly for fuel for the steamships that plied the Queensland coast, and partly for timber to build the houses of the early settlers. A similar fate befell most of the accessible hoop pines on Magnetic Island, those that remain to decorate our skylines being chiefly the ones on the rocky headlands, many of which are either too twisted to be useful for sawing into timber, or too difficult to get to. The Spitfire, Captain George Elphinstone Dalrymple, is recorded as having landed on Magnetic Island in 1860 to effect repairs, which included felling a hoop pine for a new mast. A few fine specimens of the tree still stand – there is one in my garden.

There is a good deal of misinformation about this species on the internet, some sites claiming that the trees grow very slowly, do not produce cones until they are about 200 years old, and live to about 450 years. In fact, they are quite fast growers for conifers, especially when growing under plantation or garden conditions, and evidence provided to me by Stephanie Horton, of northern NSW, suggests that they produce cones much earlier than that, certainly by the time they reach 50 years, and probably in some cases as early as 5-15 years after growing from seed. I suspect that trees grown under plantation or similar conditions mature much earlier than those clinging precariously to thin soil on rocky outcrops.

When growing in suitable positions, these trees can reach 60 m in height. The fact that the bark splits horizontally at regular intervals gives them their common name of ‘hoop’. Branches are produced along the trunk in whorls, and there is much variation in the growth habits and appearance of the trees depending on their location. Small, rigid, sharply pointed, incurved leaves produce a snakeskin-like effect.

This cone is 8–10 cm long and 6–8 cm in diameter, shaped rather like a hand-grenade, and is very prickly to handle. Cones take about 18 months to mature, and ripen from December to February; if left on the tree, they disintegrate into flattened, winged seeds, which are dispersed by the wind. The seeds contain edible nuts.

Unfortunately, the over-population of sulphur-crested white cockatoos on Magnetic Island is very fond of biting off the cones while they are still green, and they litter the ground under the trees. The cockatoos also damage the trees considerably by defoliation. They would do much better to allow the cones to mature, when the nuts could contribute to their diet. The flock of black cockatoos that visit us from the mainland does a much better job, removing the seeds systematically from the tip of the cone, often leaving a bare axis.

2015, being exceptionally dry, was a good year for the production of female cones, and for once the white cockatoos did not de-cone the trees in Geoffrey Bay (they were too busy removing hundreds of green cones from the large tree in my garden). This has enabled a good number of cones to mature on the trees, and an extra-large visiting flock of black cockatoos has been able to harvest the ripe seeds for food.

In 2013 Matt and Rachel Cole, who own an area of mixed woodland in the Coff's Harbour hinterland, sent me a photograph of damage sulphur-crested white cockatoos had done to a number of their hoop pines, ringbarking them in the upper part of the tree. This resulted in the treetop dying off and falling down, leaving a jagged stump. My first reaction was that the cockatoos were simply being mischievous, and that the trees would die off. This has not proved to be the case. All of the trees concerned have fully recovered, and have put out lateral branches from the residual stump. It would appear that the cockatoos were attacking the bark to feast on some insect that was infesting the trees, and their ringbarking, and the removal of the insects, may actually have saved these trees from destruction. I owe those cockatoos an apology for misjudging their intentions!

The hoop pine is a gymnosperm, the type of vegetation that developed after the even more primitive pteridophytes (that produce no pollen, flowers or seeds, but reproduce by spores) dominated the earth, and in their turn the gymnosperms dominated the earth before the more efficient angiosperms, the flowering plants, took over, and forced the gymnosperms into the less fertile soils, generally on hillsides and ridges, in which habitats they are still generally found. They are the plants that the dinosaurs knew, 160 or so million years ago.

The tree is monoecious. The pollen cones are from 3 to 6 cm long, and grow on the tips of some of the branches. These pale green, wormlike cones consist of scores of pollen-filled scales arising from a string-like axis. In due course, when the pollen is released (in enormous, very inefficient quantities), it will be carried by the wind (not by insects, birds, or other pollinators) in the hope that a few grains might alight on a tiny seed cone that is just in its formative state, when it is no wider than the branch on whose end it grows, and therefore hard to distinguish from the rest of the foliage. In many conifers, the pollen cones are carried on the topmost branches, so that the blown pollen has the chance to fall on the seed cones. In hoop pines, however, the pollen cones are carried on the lower branches, and the seed cones on the higher branches. This may well be because most of our trees grow on hillsides, where there is generally an up-draught of wind to carry the grains of pollen upwards. The pollen grains are equipped with two tiny, ear-like flaps that improve their ability ride on the wind. As the pollen is discharged, the pollen cones lose their green colour and droop down, and finally, bereft of pollen, fall off.
Once a seed cone is pollinated, and the male gamete has united with the female gamete in the ovule, the seed cone begins growing, and (in the case of our trees after 18 months or so) ultimately becomes the bristly grenade-like seed cones we seldom see, so high are they on the trees, unless they have been chewed off by a cockatoo and dropped to the ground, usually with some of the unripe seeds having been eaten by the cockatoo. They don’t drop naturally until they  have ripened, and, unless they land on something particularly soft, they shatter on impact to disperse the seeds.

The foliage on young trees is very different from that on older trees. The ‘needles’ are still separate on the branches, and the branch is much flatter, as can be seen in the photograph.

A major problem when trying to study these pines, so iconic of the island, is that all the interesting stuff goes on at a great height, and so is difficult either to examine closely or to photograph clearly. This situation is eased if one can be on a slope upwards of the trees, and this is possible to a certain extent on the new walkway between Nelly Bay and the Rocky Bay lookout, where many of these photographs have been taken.

The growing tip of the tree is interesting. In its early stages, it looks like a straight rod. The tip then develops juvenile foliage, which slowly turns into the typical tree-top with which we are familiar.

The Hoop Pine provides food for several caterpillars of Lepidoptera, including the Castor or Croton Caterpillar Achaea janata, which can be a pest on seedlings, and the Hoop Pine Seed Moth Hieromantis ephodophora, which has been found feeding upon the tiny female seed cones and the seeds.

The trees do well in plantations, and have been so grown in Queensland since 1917. There are currently about 44,000 hectares of plantations. The largest plantings are around Brisbane, Gympie, Maryborough, Murgon and Monto. There are smaller plantations in North Queensland, mainly on the Atherton Tableland. Plantations are also found in PNG and in northern NSW. The timber is a first-class softwood that varies in colour from almost white to cream or even light brown, with little difference between heartwood and sapwood, although the former is a little darker. The wood is fine and evenly textured, with a straight grain. The growth rings are visible but not distinct, and the figure is plain or mottled. The timber has low shrinkage as it seasons. It machines and turns well, but is not suitable for steam bending.

In some specimens, resin can be seen exuding from the tree. Aborigines used the sap from the trunk as a cement, after warming it up with their fingers.

Photographs taken in Rocky & Picnic Bays 2005-2010, Geoffrey Bay 2015, Coff's Harbour hinterland 2013-2016
 Page last updated 14th December 2016