AS 2303 PART 3. THE MATTER OF BALANCE IN TREES
While most criteria found in AS 2303 mirror those found in NATSPEC, even if they have been relaxed a little at times, the one area where there has been significant change is in the application of the criterion for tree stock balance.
It is widely recognised that the root system should be appropriate for the size of the tree it needs to support. Under NATSPEC, the size of the tree above-ground was assessed as being its ‘Size Index’. Size Index is calculated by multiplying a tree’s Height(m) by its Calliper(mm). See ‘Understanding the Concept of Size Index’. To conform to the NATSPEC balance criterion for any given rootball volume, the above-ground size of the tree it ‘needed to support’ was restricted to a narrow ‘size index’ band. Under AS 2303:2018, the concept of size index has been continued, but the recommended (not binding) range of acceptable Size Index (“the preferred range”) has been expanded considerably. For a tree to be considered an appropriate size for its container, it may be significantly smaller or somewhat larger than was acceptable under NATSPEC. This expansion of acceptable sizes makes supplying conforming trees more manageable and allows those species that root out vigorously (e.g. Waterhousias) to be supplied as fresher and more vigorous stock. Putting size above ground to one side, the important further requirement is that the root system should have fully occupied its container.
Trees Impact’s production practices have been developed around the NATSPEC Specification for trees, and our main production nursery, Karignan Plantation, has been laid out specifically to allow conforming trees to be grown by highly qualified and stable staff and under its externally audited ISO 2001 Quality Management System. Our trees have long been regarded as the best available.
How then does the implementation of AS 2303:2018 impact our trees? The answer is: ‘not a great deal’ because our current production practices are already more than well suited to the new standard. While there is no strict requirement to do so, Trees Impact will, of course, be supplying trees only where their Size Index clearly falls within the preferred range as found in AS 2303:2018
In summary, the quality targets and practices that have been our commitment for the last 27 years will continue unabated and, on request, we will willingly certify our trees as AS 2303 compliant – without extra charge.