It often grows in pure stands in tall wet forest, sometimes with rainforest understorey, and in temperate, high rainfall areas with deep loam soils.

[13] Von Mueller did not designate a type specimen, nor did he use the name Eucalyptus regnans on his many collections of "White Mountain Ash" at the Melbourne Herbarium.

Victorian botanist Jim Willis selected a lectotype in 1967, one of the more complete collections of a specimen from the Dandenong Ranges, that von Mueller had noted was one "of the tall trees measured by Mr D. Boyle in March 1867.

[14] The brown barrel (Eucalyptus fastigata) is a close relative of mountain ash, with the two sharing the rare trait in eucalypts of paired inflorescences arising from axillary buds.

[16] Further analysis of the same chloroplast genetic markers by researchers at The Australian National University suggests that there is more natural haplotype diversity in the Central Highlands of Victoria than previously observed.

[17] This suggests that gene flow is likely to be occurring over long distances, and that the lengthy generation times of the species has precluded the development of substantial genetic differentiation between Tasmania and the mainland.

[17] In Victoria, stands of tall trees are found in the Otway, Dandenong, Yarra and Strzelecki ranges as well as Mount Disappointment and East Gippsland.

[24] Other trees it grows with include manna gum (Eucalyptus viminalis), shining gum (E. nitens), myrtle beech (Nothofagus cunninghamii) and silver wattle (Acacia dealbata)[8] The mountain ash-dominated forest can be interspersed with rainforest understory, with such species as southern sassafras (Atherosperma moschatum), celery-top pine (Phyllocladus aspleniifolius), leatherwood (Eucryphia lucida) and horizontal (Anodopetalum biglandulosum).

However, growth rates slow with age, and eventually turn negative as old trees senesce and the tops of the canopy are damaged in high winds, lightning strikes or during fires.

[26][27] A number of environmental factors influence the growth and maturation of E. regnans, with research showing that the amount of incident solar radiation is positively associated with height and stem diameter growth, and that the amount of sunlight received is strongly negatively correlated with the level of precipitation (although all areas studied still received more than 120 centimetres (47 in) of rainfall).

[27] Historically, low-frequency and high-intensity wildfires (ignited by lightning strikes) would prevent many stands from reaching this age, with fires killing mature overstorey trees and a new cohort developing from canopy-stored seedbanks.

Despite this, natural variation in the spatial scale and frequency of wildfires meant that 30-60% of pre-European E. regnans forests would have been considered old growth (e.g. with living trees more than 120 years old).

As E. regnans is often the sole or dominant overstorey tree in many locations, this can lead to the replacement of a tall wet open forest ecosystem with a dense low wattle shrubland, which obviously has large repercussions for community composition and function.

As contemporary fire regimes have been highly modified since European occupation of Australia, there is a clear risk to E. regnans forests in many regions.

[32] The majority of the endangered Leadbeater’s possum population lives in mountain ash forests (Eucalyptus regnans, E. delegatensis and E. nitens) in the Central Highlands of Victoria.

[36] In a small area of rainforest in Yarra Ranges National Park in Victoria, nine epiphyte species were observed growing on Eucalyptus regnans, the most prevalent of these being the liverwort Bazzania adnexa.

[38] Stressed trees can be damaged by the eucalyptus longhorned borer (Phoracantha semipunctata), which burrows into the trunk, which exudes a red stain.

[39] A study carried out by environmental scientist Professor Brendan Mackey of the Australian National University in 2009 identified that mountain ash forests in Victoria’s Central Highlands are the best in the world at locking up carbon.

They further calculated that a E. regnans-dominated forest with trees up to 250 years old and a well-established mid-storey and upper storey could store up to 2,844 tonnes per hectare (1,132.75 long ton/acre; 1,268.68 short ton/acre) of carbon.

[46] The Cumberland Scenic Reserve near Cambarville, became the site of Victoria's tallest trees, in 1939, including one measured at 92 metres (302 ft) high, following the extensive Black Friday bushfires.

[23] In 2000, a tree at Wallaby Catchment in Kinglake National Park was discovered to be 91.6 metres (301 ft) tall in 2000,[23] however it perished in the Black Saturday bushfires of 2009.

[49] Some individuals attain much greater diameter; the largest known being "The Bulga Stump", a charred remnant near Tarra Bulga, South Gippsland district, Victoria, Australia which as a living tree had a DBH of 10.77 metres (35 ft 4 in),[50][51] making E. regnans the third thickest species of tree after the Baobab (Adansonia digitata) and the Montezuma Cypress (Taxodium mucronatum).

It was written on 21 February 1872, by the Inspector of State Forests, William Ferguson, and was addressed to the Assistant Commissioner of Lands and Surveys, Clement Hodgkinson.

Ferguson had been instructed to explore and inspect the watershed of the Watts River and reported trees in great number and exceptional size in areas where loggers had not yet reached.

In one instance I measured with the tape line one huge specimen that lay prostrate across a tributary of the Watts and found it to be 435 feet from the roots to the top of its trunk.

Primary uses for sawn wood are furniture, flooring (where its very pale blonde colour is highly prized), panelling, veneer, plywood, window frames, and general construction.

Several applications have been made to Victoria's Flora and Fauna Guarantee (FFG) Scientific Advisory Committee to list mountain ash forests as an endangered vegetation community.

In the early 1960s they set up a new series of paired catchment experiments in wet mountain forests near Healesville to measure the long term impacts of timber harvesting and bushfire on water quality and quantity.

[39] American horticulturist and entrepreneur Ellwood Cooper noted its rapid growth but demanding soil requirements in his 1876 work Forest Culture and Eucalyptus Trees.

[67] Eucalyptus regnans requires fertile soil with good drainage and annual rainfall of 1,000 millimetres (39 in) spread over the year, and has poor tolerance to temperatures below −7 °C (19 °F) or drought.