| Norfolk pine | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Gymnospermae |
| Division: | Pinophyta |
| Class: | Pinopsida |
| Order: | Araucariales |
| Family: | Araucariaceae |
| Genus: | Araucaria |
| Section: | A. sect.Eutacta |
| Species: | A. heterophylla |
| Binomial name | |
| Araucaria heterophylla (Salisb.) Franco | |
| Synonyms | |
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Araucaria heterophylla (synonymA. excelsa) is a species ofconifer. As itsvernacular nameNorfolk Island pine (orNorfolk pine) implies, the tree isendemic toNorfolk Island, anexternal territory of Australia located in thePacific Ocean betweenNew Zealand andNew Caledonia. It is not a truepine, which belong to the genusPinus in the familyPinaceae, but instead is a member of the genusAraucaria in the familyAraucariaceae, which also contains thehoop pine and themonkey-puzzle tree. Members ofAraucaria occur across the South Pacific, especially concentrated in New Caledonia (about 700 km or 430 mi due north of Norfolk Island), where 13 closely related species of similar appearance are found. It is sometimes called astar pine,Polynesian pine,triangle tree orliving Christmas tree, due to its symmetrical shape as asapling.
The first European known to have sighted Norfolk Island was CaptainJames Cook. In 1774, on his second voyage to the South Pacific inHMSResolution, Cook noted the presence of large forests of tall, straight trees that appeared to be suitable for use asmasts andyards for sailing ships. However, when the island was occupied in 1788 by convicts transported from Britain, it was found that Norfolk Island pine trees were not resilient enough for such use and the idea was abandoned.[2]
In the late 1950s, a trial shipment of Norfolk pine logs was sent to plywood manufacturers in Sydney, New South Wales, with the hope of developing a timber export industry on Norfolk Island. Although the plywood companies reported excellent results, the industry was deemed notsustainable by the Norfolk Island Advisory Council, which decided to reserve timber production for local use. The timber is good forwoodturning and, together with the similarCook pine, is extensively used byHawaiian artisans.
The tree is slow growing and can reach a height of 50–65 m (160–210 ft), with straight vertical trunks and symmetrical branches, even in the face of incessant onshore winds that can contort most other species. From the straight trunk, it emits five almost horizontal or slightly oblique branches, forming floors; the plane of each floor is a perfectpentagon. If kept indoors, the tree remains smaller. The grey-brown bark falls off in fine scales. The branchlets are four to seven in regularwhorls.
The youngleaves are soft andawl-shaped, 1–1.5 cm (0.4–0.6 in) long, about 1 mm (0.04 in) thick at the base on young trees, and incurved, 5–10 mm (0.2–0.4 in) long and variably 2–4 mm (0.1–0.2 in) broad on older trees. The thickest, scale-like leaves on coning branches are in the upper crown. Thecones are squat globose, 10–12 cm (4–5 in) long and 12–14 cm (5–6 in) diameter, and take about 18 months to mature. They disintegrate at maturity to release thenut-like edibleseeds. The seeds have a length of 2.5 to 3 cm (1.0 to 1.2 in) and a diameter of about 1.2 cm (0.5 in) with wide wings. There are fourcotyledons present. It is adioecious tree (male and female cones in different plants), although it can also bemonoecious.
The scientific nameheterophylla ('different leaves') derives from the variation in the leaves between young and adult plants.
The distinctive appearance of this tree, with its widely spaced branches and symmetrical, triangular outline, has made it a popular cultivated species, either as a single tree or inavenues. When the tree reaches maturity, the shape may become less symmetrical. Despite the endemic implication of the species nameNorfolk Island pine, the species is widely planted as an ornamental tree for its exotic, pleasing appearance and fairly broad climatic adaptability, and now occurs throughout the world in regions with suitableMediterranean andhumid subtropical climate. It grows well in deep sand, as long as it receives reliable water when young. This, and its tolerance ofsalt and wind, make it ideal for coastal situations. Indoors, the plant needs a bright location with at least 40% but preferably above 60% humidity for good growth. Indoor trees must not be exposed to the scorching sun or dry air from a radiator; the temperature should ideally not exceed 22 °C (72 °F). In winter, the plant needs a bright room that should be around 17 °C (63 °F).[3]
Many of the "Norfolk Island pines" that grow in Hawaii, including their descendants used as potted ornamentals on the U.S. mainland, are actually the closely relatedCook pines native toNew Caledonia, the two species having been confused when introduced.[4]
Young trees are often grown ashouseplants in areas where the winters are too cold for them to grow outside (they will not, for example, survive outdoors in most ofNorth America orEurope), and are sometimes used asChristmas trees. It will not survive in areas subject to prolonged cold. However, there are a few specimens growing outdoors in the subtropical gardens ofTresco Abbey Gardens on theIsles of Scilly, in the United Kingdom. What is probably the most northerly specimen growing outdoors is a young tree onValentia Island on the southwest coast ofIreland. The tendency for pottedsaplings to develop a barren appearance can be helped by growing them in clumps. In northern climates they can be left outdoors during summer or placed under growing lights to promote fuller growth.
When planted outside, the trees should be provided with adequate space, as they can grow to a large size. The trees are widely planted in coastalSouthern California, where they can grow to well over 30 m (100 feet).[5] The trees are commonly confused withAraucaria columnaris.[4]
Araucaria heterophylla has gained theRoyal Horticultural Society'sAward of Garden Merit.[6]
The species survival is not threatened at all by the houseplant trade, as it is grown commercially for potted plants. However, the native, natural stands ofA. heterophylla were always restricted and have been much reduced since Capt. Cook's time. Farming, poor land management and the introduction of invasive species have reduced its population on the original three islands considerably. The main remaining stands are now within Norfolk Island National Park and are therefore under some protection. TheIUCN classifies the species asvulnerable.[1] Seedlings of this species are starting to turn up under native coastal forest in the North Island of New Zealand, adding this species to the already numerous species of "Wilding Pines" that are a huge issue in that country.
