What was it all about?

Macadamia trees need to be kept small and productive with light reaching the orchard floor to promote groundcover, which reduces erosion.

This project planted a new orchard of two varieties (one upright and one spreading) to evaluate four techniques that can be used to control tree size…

• Early tree training
• Root pruning
• Trunk girdling
• Strategic timing of hedging.

Key findings were…

• The current industry recommendation, to train young trees to a central leader, was found to result in yield losses during the early years of production. Minimal pruning, focusing on the removal of bad crotch angles, may be a better approach.
  
  
• Root pruning slows the growth of trees without reducing yield, but more work is needed before it can be recommended commercially, especially in terms of suitable machinery and frequency of pruning.
  
  
• Trunk girdling slowed the growth of trees without reducing yield. The technique might be adopted immediately, but would benefit from further research into the width and depth of the girdle.
  
  
• The current industry recommendation of hedging trees in late spring or early summer to avoid competition between early fruit development and the post-hedging flush, was found to be too simple. Researchers did not detect differences in cumulative yields for trees subjected to annual pruning at different times of the year, but they did find significant yield differences between treatments in some years. Researchers concluded that the industry recommendation should stand, but there are clearly complexities here that need further examination.