The Full Bottle

One of our venerable Queensland Bottle Trees (Brachychiton rupestris) is showing signs of ageing, and it’s more than a wrinkle or two. The tree in question looks across Farm Cove towards the Opera House and Harbour Bridge.

Recently we noticed a large vertical crack opening up on the south-eastern side of the trunk. You’ll notice from this photograph taken in 2006 that from this view the trunk has always looked a little buttock-like!

Before we took remedial action we wanted to find out how sound the tree was overall, and whether any amount of cabling and bracing would prolong its life substantially – and without risk to our visitors.

The good news is that in this case something can be done. The diagnosis didn’t come cheap, or without risk to the tree. We brought in a 'sonic tomograph' expert to – carefully and strategically – bang some nails into the tree.

Our Sonic Tomographers then measured how well sound waves moved through tree, giving them a qualitative measure of what they call the ‘structural integrity’ of the trunk. The test reveals active fungal activity and decayed wood that is not otherwise visible. We can then answer the important question: how likely is it that this tree will fall down or fall apart, soon?

Sonic Tomography is not something you, or we, should do to an obviously healthy tree. There is always a risk of fungal or bacterial infection through the nail holes. In this case, though, the tree needed some tough love.

Although the test found some decay and fungal activity, 75% of the tested area was sound. The fungi had most likely entered through the vertical split in the trunk.

The report also notes in passing that the inside of a Queensland Bottle Tree is a little like a palm in that it has little lignin (the cell wall chemical that gives the wood in most its toughness) and lots of water. This means the test tends to overestimate the damage, supporting the decision to not condemn this tree.

One further invasion of the tree will be needed, to drill the trunk for bolting. Then, we hope and expect, the tree can live out many more years of useful and tranquil existence in the Royal Botanic Gardens.


Kimberly said…
Such a beautiful tree...and interest! Cetainly worth saving!!
Tim Entwisle said…
We'll do all we can!
I've always wanted to see one of those in person... maybe a south florida botanical garden has one I can see.
Tim Entwisle said…
They should be able to grow this species, or perhaps one of the (more Tropical) Adansonia species (the Boabab or Boab) which are equally striking.
Chris said…
I've never heard of such efforts to save one tree. Amazing.

I'm not even sure that sort of tree diagnosis exists here.