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When Pruning is Required
In any situation where trees grow in proximity to people, buildings and infrastructure the need to prune is inevitable. Pruning may be necessary to control growth, remove deadwood, improve form or vigour and maintain safety. Pruning may enhance the function and performance of trees in the landscape, by increasing timber quailty, flower and fruit production and overall aesthetic/visual appeal.
The requirement to prune trees may differ between commercial production and domestic landscape situations - each have differing needs and outcomes. Regardless of the reason the principles of pruning and the tree's response to our actions remain the same. Commercial pruning methods designed specifically to induce flowering, increase fruit yeild and allow ease of access to crop collectors or machinery are not discussed here. Neither is manipulative pruning such as hedging, pleaching, topiary and espaliers - well covered elsewhere by authors like Patrick (1990).
Ideally, trees in urban landscapes require minimal pruning intervention where they are well sited and suited to their location. However, more often in our towns and cities trees closely associated with buildings, services and visual sightline obstructions invariably need proactive pruning. An outline of common canopy pruning operations is given:
Deadwooding - removing dead branches to reduce the supply of material available to destructive pests and agressive pathogenic diseases, improve appearances, eliminate hazards.
Crown Thinning - selective partial or complete removal of branches to increase light penetration, improve air circulation, lessen wind resistance, reduce weight. Figure 4.
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| Crown Lifting - raising the lower level of the canopy to provide clearance for pedestrians, vehicles, buildings, signage, views. Figure 5. |
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Crown Reduction - pruning back leading and lateral stems to reduce height and maintain prescribed dimensions, whilst retaining structural integrity and natural form. Figure 6.
Additional variations on these pruning operations exist. In many cases trees require a combination of pruning treatments to achieve the desired result. Various site factors and the actual reasons for pruning will determine the final outcome. |
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Understanding More Means Doing Less
This general overview was intended only to improve your awareness of acceptable tree pruning techniques and the effects of such operations in terms of wound responses. Further reading may provide valuable insights in to tree mechanisms and reactions and is recommended in order to more clearly understand the complexities of the concepts presented so briefly here.
For every action there is an opposite reaction. Trees live with finely tuned biological systems and processes in constant motion. Pruning initiates a complex chain of internal chemical responses, all of which require precious energy taken at the expense of some other function. Understanding trees as dynamic organisms within a perpetual cycle of succession enables us to make the right decisions about maintenance - to ensure we don't needlessly add another burden. For trees - considering the competition - life is tough enough.
Copyright Bryan Gould
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