What Makes A Good Arborist?

If we are talking about arborists at AQF Level 3 whose job it is to prune trees, then the most basic answer is:

Good Pruning Cuts!

Lopped Street Tree
Figure 1. This Street Tree may well have had its potential longevity shortened by decades because the pruning cuts are poorly positioned.

A Story of Poor Pruning

I was driving back from the coast after a relaxing weekend.
Life is good!
The sun was warm and there was but a gentle breeze despite it being mid-June.
Some of my favorite music was playing on the CD.

…and then, as I drove into town,

I gradually became aware that all the Street Trees along the highway had fresh pruning wounds.

The more I saw, the more I was starting to think that they were more ‘wounds’ than ‘pruning’.

Then I saw this one.

I could no longer just ignore it as someone else’s problem.
Such blatantly poor was the tree work that it needed to be brought to someone’s attention.

To get the pruning wounds so wrong can only be ignorance.

Either ignorance of what is right or ignorance of why getting it right is important.
It takes no more effort to do it correctly.
If one knew how to do it correctly you wouldn’t go to the trouble to do it poorly, would you?

Closeup of flush cuts
Figure 2 A closer view of the Ash Tree. The yellow dotted line illustrates how a correct cut would look if the other branch were to be removed correctly.

Position of the Final Pruning Cut is Important

Traditionally arborists did their cuts like those on this tree.

The supervisor would say ‘Make those cuts flush’ and then they would paint them with ‘Wound Dressing’.

What happened then?

Well, often decay entered the wound causing gradual but catastrophic damage that often led to the premature loss of the tree.

So the experts developed rules about when and how to prune different tree species and books were written.

The correct positioning of the final pruning cut outside the branch collar is the single most important advance in arboriculture in the last 100 years…


And then along came Shigo…

A correctly positioned pruning cut.
Figure 3 A correctly positioned pruning cut.

Professor Alex Shigo that is.

He spent years cutting up trees to see what no-one else had thought to see.
Simply by cutting longitudinally rather than transversely he revealed much that others had not noticed.

Shigo’s main discovery was that trees can protect themselves when wounded.
When branches are removed, they do it best at a point in the collar.

What flush cutting does is removes the collar and prevents the tree from effective self-protection.

It is not my intention here to go into Shigo’s work or his theories and models, for it is available in any books on pruning written in the last thirty years.

For pruning like that seen in figure 2 to occur indicates that the person doing the pruning is decades out of date with their understanding of how trees should be pruned.

A good summary of the correct positioning of the final cut is available in the Australian Standard AS4373-2007 Pruning of Amenity Trees.


If you would like to learn more or feel that you require advice regarding your trees.
Please contact us via email or phone (02) 6161 1800.