Judy Fakes

The development of an Australian Standard is a lengthy and detailed process involving representatives from relevant groups and organisations, an officer from Standards Australia and extensive public comment and consultation. The development and current review of AS4373 Pruning of Amenity Trees is no exception.

This paper gives some background to the development of AS4373 and summarises the major changes in the review submitted for public comment in 2006. At the time of writing of this paper, the responses from the public consultation period have not been reviewed by the committee.


Rumour has it that AS4373 started its life as a conversation between two blokes sitting chatting on a log one sunny day in 1989. Their conversation concerned the need for work performance standards for the tree service industry. They set to work on the British and American Standards for tree work and came up with a draft document. This document was put to the National Arborists Association in NSW for their comment and later sent to the Arboricultural Association in Victoria. After further comments and amendments it was forwarded to the Australian Standards Association.

After the formation of a committee, this document was released for public comment in 1991. The retirement of the secretary of the committee in 1992 saw the document disappear until late 1993. In 1994, a working group was set up to review the ‘marginal’ document under a new secretary form Standards Australia, Ms Anne Hawes. The working group consisted of representatives from the Arboricultural Association of Victoria, the Australian Institute of Horticulture, the Local Government Tree Resources Association, The National Arborists Association of Australia and the Ryde College of TAFE Division of Horticulture. Significant input was received from the Western Australian Arborists Association and VCAH Burnley.

In short, a red pen was taken to the original document, the language simplified, the content tightened, the definitions culled and diagrams detailed. It was finally published in 1996 – seven years after its inception.

In 2005 it was decided that the Standard needed to be revised. A new working group was established under a newly formed committee set up for the arboriculture industry. The result of that review process is that the revised document was put out for public comment in June 2006. The period for public comment closed on 31st July 2006.


This Standard was developed to provide a guide for the pruning of amenity trees based on the widely accepted theories of compartmentalisation of decay/ dysfunction in trees (CODIT). Its aim is to encourage correct and uniform pruning practices.

The original edition covers general pruning, thinning, deadwooding, formative pruning, reduction pruning, crown lifting, pollarding, remedial pruning and line clearance. It includes diagrams to clarify points, particularly with respect to the position of the final cut. Importantly, it also makes it clear as to what must be specified when instructions for tree work are being formulated.

It is not a technical instruction, that is, it is not a step-by-step guide to the removal of branches. It does, however, highlight the outcomes of correct pruning practices and associated work. The document assumes some knowledge of the practices of tree pruning and the theory of CODIT.

The scope clearly states what is and isn’t covered by the Standard. The document also states that lopping and topping are unacceptable practices. This has proven to be of great use to tree management officers who have to convince home-owners that they will not be given approval to lop their trees.

The Standard was intended for use by anyone specifying and or performing tree pruning.


Some of the major points of the original document are:

  • When removing a branch, the position of the final cut should be a clean cut to the branch collar or, in the absence of a collar, to a position determined by the branch bark ridge. Final positions for reduction pruning and the removal of a co-dominant stem are also shown and described.
  • Climbing spikes are not to be used on or in sections of the tree to be retained.
  • Lopping and flush-cutting are unacceptable practices
  • Clarification of what must be specified for the various types of pruning – for example, the minimum diameter of branches to be removed if dead-wooding is being carried out.


It was felt by the committee and the working group the original document was fundamentally sound, however, after almost ten years of use, there were clearly areas that needed tightening up.

Definitions have been reviewed and added and revised where necessary. The diagrams have been redrawn to make them look less like lopping. General pruning was deleted as it was considered that this type of pruning created an opportunity for over-pruning of a tree and was too open to interpretation.

Most importantly, section 4 – “considerations before pruning” has been expanded and tightened to include the minimum level of arboricultural qualifications that the person determining the need for pruning should have is AQF level 3. The criteria to be considered are expanded and a note stating that the pruning of the tree should not be detrimental to the health or structure of the tree is included. The future pruning requirements of the tree are also to be considered.

“Remedial” pruning has been given the additional title of “restorative” pruning as the word ‘remedial’ is often loosely used. Line clearing is now only formative or reduction pruning.

New sections on the pruning of palms, the unnecessary painting of wounds and a general comment on root pruning have also been included. The committee debated the inclusion of a detailed section on root-pruning but concluded that much work was still to be done in this area and that waiting for it to happen would considerably delay the review of AS4373. The opportunity exists to have a “part b – Root Pruning” included at a later stage.


AS4373 is still the only Australian Standard relating to trees. There are several others in draft form. My feeling is that the pruning standard has made a difference to the quality of tree work. However, I know that the document is still poorly used and quoted. It is not enough to say “prune to AS4373”; the document must be ‘driven’ and the specific types of pruning more closely specified. Many councils in Sydney allow a 10% prune of a tree when residents request that they be allowed to prune their trees even if the tree doesn’t require pruning. This is not a component of AS4373.

Pruning of Amenity Trees is a document written in plain English. It is essential that anyone specifying or performing tree work understands the Standard and knows how to apply it to the work that is required.



  1. Angelica on August 22, 2021 at 4:13 pm

    Also, cut at the correct distance. Always make cuts just above a bud, but not so close that you risk damaging the bud. Don’t cut too far above it, as water can get trapped in the stub and lead to rotting. As a general rule, cut above the bud at a distance of about a quarter of the thickness of the stem. Here at Wilson Tree Service Pros, rest assured that we’ll deliver excellent craftsmanship.

  2. Mae on September 21, 2021 at 9:33 pm

    Arborist can be a great help especially if you do not want to prune your trees. When you are not equipped well and do not know more about tree pruning, then I can suggest that you ask an arborist. They are a great help for this situation.

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