Tree Pruning/Thinning

Pruning a tree may seem like a fairly simple straightforward procedure.

Tree Thinning and PruningIn contrast, cuts to the tree must be made with a clear understanding of how the tree will respond.  When a tree experiences trauma (Being cut) it releases chemical compounds called hormones that sign the tree to respond in different ways. Where, how and when the tree is cut or pruned effect these chemical signals.

There are a few things that must be taken into account before the tree is pruned. First, what are the owner’s objectives and or goals of pruning? Examples of common goals for pruning include:

  • Reduce risk for tree branch failure
  • To provide clearance
  • Reducing shade and or wind resistance
  • Maintaining the health of the tree
  • Influencing flower or fruit production
  • Improving a view
  • Improving aesthetics

Second, does the owner understand the effects pruning will have on the tree. Effects included but are not limited to:

  • Loss of stored energy of the tree.
  • Reduction of photosynthetic capacity
  • May reduce overall growth
  • Possible dwarfing effect
  • Unpruned parts tend to grow more than they normally would have – shoot invigoration.

Lastly, are correct pruning practices being employed by the tree care professional? Basic practices include:

  • Pruning branches at the correct location which is the branch protection zone. This adds in compartmentalization of the tree, minimizing the spread of decay.
  • Being mindful of co-dominant branches and lack of branch bark ridge. Removing a branch like this can increase the risk of decay.
  • Using the correct pruning cut.
  • Applying safe work practices.
  • Avoiding flush cuts, which damage the tissue of the tree.
  • When possible avoid reduction cuts.

Types of Pruning

  • Structural Pruning – most come in young trees. Adds in correct form development for given species.
  • Pruning Mature Trees – Many factors to consider – site, time of year, species, size, growth habit, and vitality, as well as maturity of the tree.
  • Crown Cleaning – selective removal of dead, diseased, broken, or weakly attached branches from the crown. Most common.
  • Crown Thinning – crown cleaning and selective removal of branches for increased light and air movement, also improves structure.
  • Crown Reduction – to reduce the size of the tree.
  • Crown Restoration – To improve structure from past pruning such as topping. Could take many prunings over many years.
  • Utility Pruning – Removal of branches to prevent loss of service, prevent damage to utility equipment, or provide access for workers.

Topping is cutting back a tree to a predetermined crown limit, and is not a recommended pruning practice. Most common reasons not to top a tree are:

  • Starvation – cuts off food making ability.
  • Shock – May be scolded by the sun.
  • Insects and Disease – The stubs are highly vulnerable to decay and insects.
  • Weak Limbs – New limb is weaker then prior limb.
  • Rapid New Growth – Tree starts to produce what are known as watersprouts.
  • Tree Death – Beeches are a good example of possible tree death. Some species cannot recover from the massive trauma of topping.
  • Ugliness – Never regains the form and function of the species before topping.
  • Cost – Upfront costs are low but long term topping is expensive. It can lower property value, increase maintenance cost etc.