How Tall is the Tallest Flowering Tree? – Giant Tree Expeditions: Tasmania

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(Video recordings are additionally available)

Fieldwork by YD Bar-Ness and S. Pearce. Text and calculations by YD Bar-Ness, photographs by S Pearce, The Tree Projects

The world’s tallest known flowering plant and the tallest tree in the Southern Hemisphere is a Eucalyptus regnans growing here in Southern Tasmania. It’s been named Centurion in honour of the ancient Roman officers who commanded groups of a hundred soldiers. There used to be even taller trees, but Centurion is the tallest flowering plant that we know of alive on Earth today. There’s no formal program to remeasure these trees regularly, so we went out as volunteers to help keep track of their health and condition.

It was last measured at 99.82 metres in 2014, so we wanted to find out if it had grown taller than 100 metres.

We used a portable laser rangefinder to shoot more than 300 laser measurements of the tree. We did our best to use averages to help us accommodate for the inevitable inaccuracies involved in any precision measurements.

Because there was no point in the forest where we could see the entire tree from top to bottom, we had to do this in four stages.

We started at the bottom and chose a reference point. We made our best determination of its height as 0.765 m above the ground.

We measured a “Strong Fork” that was visible from the base of the tree and further up the hill. We made our best determination of its height at 28.125 m.

We found a distinctive point called “White Shield” that was far up the stem and we could spot at the same time as “Strong Fork”. We measured the vertical distance between these two landmarks and made a best determination of the White Shield’s height at 59.775 m.

We climbed up the steep hillside looking for a gap in the forest where we could clearly see the top of the tree. At three spots, we took measurements where we could see both White Shield and what appeared to be the highest leaves of the tree. This was the topmost of our four height components.

We used the laser rangefinder to scan the top of the tree for the highest point, and recorded the highest height that we could repeat with five separate shots.

We observed clearly that the trunk of the tree had broken near the top. That means at some point in the not-so-distant past, Centurion was probably significantly taller.

We averaged the values from these three upper survey stations and came up with a height of 100.495.

We made an estimate of survey error with the help of Dr. David Caprette at Rice University (USA) to refine this number to 100.5 +/- 0.4 m. Even if that error calculation is far too low, the most likely outcome from our work is that the tree is indeed over 100 m tall!

Other measurements will certainly come in more or less, but ultimately it doesn’t mean too much to the tree itself. One hundred is just a number, but it’s also a nice landmark at which to shine a light on just how spectacular these trees are.