Eucalyptus Regnans - Tallest Specimens

Tallest Specimens

Eucalyptus regnans is the tallest of all flowering plants, and possibly the tallest of all plants, although no living specimens can make that claim. The tallest measured living specimen, named Centurion, stands 101 metres (331 ft.) tall in Tasmania. Before the discovery of Centurion, the tallest known specimen was Icarus Dream, which was rediscovered in Tasmania in January, 2005 and is 97 metres (318 ft) high. It was first measured by surveyors at 98.8 metres (324 ft) in 1962 but the documentation had been lost. 16 living trees in Tasmania have been reliably measured in excess of 90 metres (300 ft).

Historically, the tallest individual is claimed to be the Ferguson Tree, at 132.6 metres (435 ft), found in the Watts River region of Victoria in 1871 or 1872. This record is often disputed as unreliable, despite first-hand documentary evidence of it being measured on the ground with surveyor's tape by a senior forestry official (see below). Widespread agreement exists, however, that an exceptionally tall individual was reliably measured at 112.8 metres (370 ft) by theodolite in 1880 by a surveyor, George Cornthwaite, at Thorpdale, Victoria (the tree is known both as the Cornthwaite or Thorpdale Tree). When it was felled in 1881, Cornthwaite remeasured it on the ground by chain at 114.3 metres (375 ft). The stump was commemorated with a plaque that exists today. That tree was about 1 metre shorter than the world's current tallest living tree, a coast redwood, 115.55 metres (379.1 ft).

The tallest specimens of this and many other species encountered by early European settlers are now dead as a result of bushfires, logging and advanced age. Few living specimens exceed 90 metres (300 ft); old records of logged trees make varied claims of extreme heights, but these are difficult to verify today.

Most of those claims come from Victoria. Al Carder, notes that in 1888 a cash reward of 100 pounds was offered there for the discovery of any tree measuring more than 122 metres (400 ft). The fact that such a considerable reward was never claimed is taken as evidence that such large trees did not exist. Carder's historical research, however, revealed that the reward was offered under conditions that made it highly unlikely to be collected. First, it was made in the depths of winter and applied only for a very short time. Next, the tree had to be measured by an accredited surveyor. Since loggers had already taken the largest trees from the most accessible Victorian forests, finding very tall trees then would have demanded an arduous trek into remote wilderness and at considerable altitude. In turn, that meant that searchers also needed the services of experienced bushmen to be able to guide them and conduct an effective search. Only one expedition actually penetrated one of the strongholds of E. regnans at Mount Baw Baw but its search was rendered ineffectual by cold and snow and managed to measure only a single living tree — the New Turkey Tree: 99.4 metres (326 ft) — before appalling conditions forced a retreat, Carder notes.

In 1911, a previously unknown report was discovered: it was written by a licensed surveyor, G.W. Robinson, who had kept his personal forestry records from six decades earlier during the 1850s in the Dandenong Ranges, near Melbourne. Robinson had arranged with loggers to notify him when they found a very tall tree, and noted that every one he measured exceeded 91 metres (299 ft), the tallest being 104 metres (341 ft). Robinson noted that the tallest trees were felled first and had no doubt that "some of the trees felled earlier would have measured quite some 400 ft".

Victoria's early State botanist, Ferdinand von Mueller, claimed to have personally measured one tree near the headwaters of the Yarra River at 122 metres (400 ft). A government surveyor, David Boyle, claimed in 1862 to have measured a fallen tree in a deep gully in the Dandenongs at 119.5 metres (392 ft), and with a diameter at its broken tip that indicated it might have lost another eight metres of trunk when it broke, for 128 metres (420 ft).

Giant mountain ash trees, Black Spur Range, Victoria. Photo: Bob Beale

Von Mueller's early records also mention two trees on the nearby Black Spur Range, one alive and measuring 128 metres (420 ft) and another fallen tree said to measure 146 metres (479 ft), but these were either based on hearsay or uncertain reliability. David Boyle also reported that a tree at Cape Otway measured 160 metres (520 ft), but this too was based on hearsay.

Many prominent botanists and tree enthusiasts have long been sceptical of such claims because they lacked first-hand evidence from a credible source. But Carder notes that nor can all the claims be considered imaginary: "The frequency, the persistence, and the wide occurrence of the reports leads to the belief that there was some basis of fact for the statements made."

None, however, had been verified by direct documentation until 1982 when Ken Simpendorfer, a Special Projects Officer for the Forests Commission, Victoria, directed a search of official Victorian archives. It unearthed a forgotten report from more than a century earlier, one that had not been referred to in other accounts of the species up to that time. 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. He wrote: "In one instance I measured with a tape line one huge specimen that lay prostrate across a tributary of the Watts, and found it to be 435 ft from its root to the top of its trunk. At 5 feet from the ground it measures 18 feet in diameter, and at the extreme end where it has broken in its fall, it is 3 feet in diameter. This tree has been much burnt by fire, and I fully believe that before it fell it must have been more than 500 ft high. As it now lies, it forms a complete bridge across a deep ravine."

Carder concludes that the height limit for E. regnans is "not greatly over 300 feet now, but there is sound evidence that trees very much taller did indeed at one time stand,".

It is also possible that individual trees will again attain such heights. Author Bob Beale has recorded that the tallest trees in the Black Spur Range now measure about 85 metres (279 ft) but — due to major bushfires in the 1920s and 30s — are less than 80 years old and have been growing consistently at the rate of about one metre a year.