The big tree

We were asked to complete a Tree Inspection on a Oak tree in a busy area near by.

The Oak tree had two types of fungus at the base of the tree, which immediately set alarm bells ringing.

The first thing we learn as inspectors is that a tree's function is to bear seeds and reproduce and that trees should be retained wherever possible in order for them to this.


As an Environmentalist of course we would want to investigate all aspects of retention for as long as possible. Which is exactly the reason why a second Investigation report was commissioned. The presence of fungal fruiting bodies caused concern. The initial tree inspection identified two species of fungus brackets (Innonatus dryadeus - which caused white rot and decay of the trunk and Fistulina hepatica, which causes brown cubical rot to the cellulose of the tree in the heartwood of the tree), these are known to cause decay, normally at the base of a tree. Last year's bracket remains were also found in the grass around the tree.

These brackets are therefore decaying both the cellulose and lignin in this tree. Where a fungus causes white rot, the cellulose can remain, but the tree can buckle under the weight. Where a fungus causes brown rot, the lignin may remain, but the wood will become brittle. In this case, both fungus bodies are decaying the tree.


The fungus is like a painting devouring the wall on which it stands, the nail and its immediate surroundings will be saved until the end (Mattheck, The body language of trees, 2015). But as you can see from the Picus Tomograph, this shows that the wall of the tree at this point where the largest fungal brackets are situated, is barely visible.

Claus Mattheck also devised a criteria for hollow tree failure, which may occur when the t/R value (t= thickness of the sound wall/ R= radius of the tree) is less than 0.3 or one third. Our Oak tree at this site does not meet the above t/R ratio. The red line on the tomography shows what would be the accepted t/R ratio. The blue, pink and green show decay.

The last picture below show the side of the cavity and cracks.

The guys worked really hard all day, not finishing until 7 pm to ensure that the site was left safe.