Reasons to Prune, How Much to Remove, and Proper Pruning Methods
Reasons to Prune
Pruning is the most common tree maintenance technique. Common reasons to prune include:
- Removal of dead and diseased branches,
- Raising the canopy to provide clearance,
- reduce the possibility of tree or branch failure,
- Maintaining health, reducing wind resistance,
- Improving a view, influencing flower or fruit production,
- Improving aesthetics.
However, trees are living organisms, and whether necessary or not, pruning creates wounds on the tree. Different tree species have different responses to pruning, and if done incorrectly, the health and shape of the tree may be altered. Pruning should be undertaken when there is a specific reason to do so.
How Much to Remove
The amount of foliage acceptable to remove depends on the tree’s species, age, size and tolerance to pruning. Younger trees tolerate pruning better than mature trees. Generally, 25% or less of the foliage should be removed at one time.
Improper pruning too often removes a large amount of leaves, which produce sugar (food) for the tree through the process of photosynthesis. The removal of too many leaves reduces the amount of sugar produced, starving the tree and forcing it to use up stored reserves.
An easy analogy is to think about energy as “tree dollars”. A tree receives a certain amount of tree dollars through photosynthesis. A healthy tree spends the dollars throughout the whole organism, from roots to shoot tips. However, when the supply of dollars is cut off due to pruning, the tree has to spend all of its dollars into restoring the crown. This doesn’t leave any for the trunk and roots.
Proper Pruning Methods
Whether pruning to remove decay, or improve a view, there are many acceptable pruning methods, such as:
Crown Cleaning: The removal of dead, dying, diseased and weakly attached branches throughout the crown of a tree.
Crown Thinning: The selective removal of branches throughout the crown to improve light penetration, air flow and crown structure. Proper thinning cuts will retain the natural form of the tree.
Crown Raising: The removal of lower branches to provide clearance for specific objects such as pedestrians, cars and buildings.
Vista Pruning: The selective removal of branches in a concentrated area of the canopy to open a specific view of an object from a pre-determined point.
Crown Reduction: The reduction of the height or spread of a tree. This is done by pruning the branch back to a lateral branch that is large enough to assume the terminal role. The lateral branch must be at least one third the diameter of the limb being reduced.
Reduction cuts must be made sparingly, as trees do not respond as well to this type of pruning. The tree cannot compartmentalize the wound as well as a branch removed at the branch collar.