Eucalyptus regnans (Mountain Ash, Victorian Ash, Tasmanian Oak or Stringy Gum) is a species of Eucalyptus native to southeastern Australia, in Tasmania and Victoria.

It is an evergreen tree growing to 70-90 m or more, with a straight, grey trunk, smooth-barked except for the rough basal 5-15 metres. The leaves are falcate (sickle-shaped) to lanceolate, 9-14 cm long and 1.5-2.5 cm broad, with a long acuminate apex and smooth margin, green to grey-green with a reddish petiole. The flowers are produced in clusters of 9-15 together, each flower about 1 cm diameter with a ring of numerous white stamens. The fruit is a capsule 5-9 mm long and 4-7 mm broad.

It occurs in cool, deep soiled, mostly mountainous areas to 1000 m altitude with very high rainfall of over 1200 mm per year. They grow very quickly, at more than a metre a year, and can reach 65 metres in 50 years. They can live for about 400 years. The fallen logs continue supporting a rich variety of life for centuries more on the forest floor.

Unusually for a eucalypt, it tends not to recover by re-shooting after fire, and regenerates mainly from seed. Severe fires can kill all the trees in a forest, prompting a massive release of seed to take advantage of the nutrients in the ash bed. Seedling densities of up to 2.5 million per hectare have been recorded after a major fire. Competition and natural thinning eventually reduces the mature tree density to about 30 to 40 individuals per hectare. Because it takes roughly 20 years for seedlings to reach sexual maturity, repeated fires in the same area can cause local extinctions.

Tallest specimens

Eucalyptus regnans is the tallest of all flowering plants, and possibly once the tallest of all plants. That claim is based on the measurement in the 1880s by the State Surveyor of Victoria of a specimen in Victoria at 114 metres; the tree was promptly cut down and the stump commemorated with an insignificant plaque that exists today. Although technically a metre taller than the world's current tallest living tree, a Coast Redwood, limits to the accuracy of measurement, made with a theodolite, are not adequate to confirm it as certainly taller. The tallest specimens encountered by early European settlers are now dead as a result of bushfires, logging and advanced age.

The largest measured living specimen, Icarus Dream, was rediscovered in Tasmania in January, 2005 and is 97 metres high (Tasmanian Giant Trees Consultative Committee, ref. 1), though it was also measured as 92 m in 2000 (Forestry Tasmania, ref. 2) so this figure retains a degree of uncertainty. It was first measured by surveyors at 98.8 metres in 1962 but the documentation had been lost. Ten living trees in Tasmania have been reliably measured in excess of 90 metres (Tasmanian Giant Trees Consultative Committee, ref. 3). Few living specimens in Victoria exceed 90 metres; old records of logged trees make varied claims of extreme heights, but these are difficult to verify today. The famous Ferguson Tree, a specimen in Victoria that fell after a bushfire, was measured by tape by a government surveyor, William Ferguson, on 21 February 1872, at 133 metres (436 feet), though this figure is not now generally accepted. Its crown had broken off and the diameter of the trunk at that point was still one metre, leading to claims that when it was intact the tree would have exceeded 150 metres (500 feet); this however presupposes that the break occurred in a hitherto undamaged tree. A more realistic scenario is of a shorter tree with several episodes of breakage and regrowth building up a stout stem without at any time attaining the claimed height.

Uses

Eucalyptus regnans is valued for its timber, not so much because of any particular virtue of the timber itself (it is a heavy, fine-grained eucalyptus hardwood much like several others), but because of the sheer volume that can be harvested. Primary uses are sawlogging and woodchipping. It was a major source of newsprint last century. Some large natural stands remain, but substantial areas of regrowth also exist and it is increasingly grown in plantations. Great controversy surrounds its use in its natural range in both Victoria and Tasmania; as the largest eucalypt of all it has symbolic value to conservationists, it provides essential habitat to important birds and mammals (notably the Lyrebird and the endangered Victorian state animal emblem Leadbeater's Possum), and in a land of vast, relatively arid plains, the contrasting lush fertility of mountain-ash forest is particularly dear to nature lovers. Although its status as a species is secure, political opposition to logging it has grown very strong in recent years (particularly in the case of woodchipping), and the extent of future harvesting remains uncertain.

See also

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• Eucalyptus delegatensis
• Manna Gum
• For other trees named Mountain Ash, see Mountain ash

References

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1. Tasmanian Giant Trees Consultative Committee New Tallest Tree for Tasmania 2005
2. Forestry Tasmania The tallest Eucalyptus regnans measured as 92 m in 2000 (.pdf file)
3. Tasmanian Giant Trees Consultative Committee Tasmania's Ten Tallest Giants 2005
4. Association of Societies for Growing Australian Plants: Eucalyptus regnans
5. Victorian Eucalypts: Eucalyptus regnans
6. International Society of Arboriculture, Australia Chapter: Australia's Biggest, Tallest and Oldest Trees

Flora of Australia | Myrtales

Rieseneukalyptus | Eucalyptus regnans