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Proper pruning methods

Justin Morgenroth, B.Sc. M.F.C.
Urban Forestry Consultant

Though the principles which dictate proper tree pruning are simple, they are often misunderstood and the resulting errors can result in irreversible damage to trees. In order to minimize the confusion and promote proper pruning techniques, this guide will answer the following questions:

  1. What branches should I prune?
  2. When should I prune my tree?
  3. How do I properly prune my tree?
  4. What tools will I require?

What to Prune

As a rule-of-thumb, no more than 25% of the crown should be removed at a time. Furthermore, the ratio of tree crown height to total tree height should be two-thirds (Fig. 1). To achieve the desired form while following the rules-of-thumb, there are seven branching defects for tree pruning to correct (Fig. 2):


  1. Epicormic
  2. Vertical
  3. Crossing
  4. Co-dominant
  5. Downward-growing
  6. Poorly-attached
  7. Dead or broken

Figure 1. When pruning lower branches, ensure that the crown height to total tree height ratio does not drop below two-thirds.


Figure 2. The green branches represent the seven types of branches that require pruning.

When to Prune

When the tree is at a young age, as early as two years following planting, pruning should begin. Pruning can continue on an annual basis until the tree has been in the ground for approximately ten years, after which pruning should occur on a five- to seven-year cycle. Though this schedule seems intensive, pruning need only occur if problem branches exist.

The optimal time of year to prune deciduous trees is during their dormant period, which in London is typically November until March (see Fig. 3). Pruning should never be carried out during spring or early summer when buds and leaves are still growing.

Figure 3. Monthly calendar showing optimal pruning times.

How to Prune

Before the proper pruning technique is described, it is crucial to understand basic branch anatomy (Fig. 4). It is important to cut in the correct location when removing a branch, otherwise unnecessary damage results. The following step-by-step approach will help to determine the appropriate location for cutting.
  1. Locate the branch that is to be removed.
  2. Find its point of attachment (branch collar) to the next largest branch.
  3. At the point of attachment, on the upper portion of the branch, locate the branch bark ridge.
  4. The cut will occur as close to, but with special care to remain outside the branch bark ridge and branch collar.


Figure 4. Basic Branch Anatomy.

By cutting at this position, two common mistakes are avoided: the stub cut and the flush cut (see Fig. 5), both of which require more time to heal, thus predisposing the tree to insect and pathogen infection.

Figure 5. Two common pruning mistakes. At left, the flush cut removes the branch collar and branch bark ridge. At right, the stub cut does not remove enough of the branch to be pruned.

One of two techniques is used depending on the size of the branch to be removed. A pair of sharp, clean pruning or lopping shears is effective for small branches (< 5cm) which can easily be supported with one hand. A pruning saw may be required for larger branches (> 5cm). In the latter case, the three-step pruning cut should be employed to avoid bark ripping (Fig. 6).

  1. Use the pruning saw to make a cut one-third of the way through the underside of the branch at least 30cm from the location of the final cut (as determined using the technique above).
  2. Outside the first cut, saw downwards all the way through the branch to be removed. Following this cut, a short stub of approximately 30cm will remain.
  3. The final cut will be made at a location just outside the branch collar and branch bark ridge.

Figure 6. The three-step pruning cut for use on large branches (> 5cm).

What Tools Will Be Necessary?

First and foremost, safety is emphasized; pruning can be dangerous and can even result in death. For this reason, the most important pruning tools are a hard hat, protective eye wear and leather gloves. In addition, pruning tools include: hand shears, lopping shears, pruning saw(s), a pole pruner (with shear or saw head attachment), chain saws, and pruning paint. There are different models of all these tools, so personal preference will come into play.

Regardless of the choice of tool, two rules must be adhered to. First, the tool must be sharp. This helps to guarantee a clean cut and prevent tearing and crushing plant tissue. Secondly, tools must be clean. Clean tools reduce the chance that pathogens will be spread from contaminated trees to healthy trees. Tools should be sanitized following every cut by dipping the tool in one part bleach diluted with nine parts water. A final cleaning with soap and water ensures that tools will not be corroded by bleach.

Finally, with the exception of oak and elm trees which are susceptible to the highly transmissible pathogens oak wilt and Dutch elm disease, wound dressing paint is unnecessary and can be harmful. Wound dressings can delay wound closure by hindering the natural protection offered by resins and gums.

By using this guide as a reference, tree pruning techniques can be ameliorated such that the three goals of pruning: safety, tree health, and aesthetics are maximized.

Pruning large trees, large branches, branches that cannot be reached from ground level, or trees near hydro wires can be difficult, dangerous, or even deadly. This work should only be attempted by professionals.

Related article: Why pruning is important

Justin Morgenroth is a consulting urban forester stationed in London, Ontario . He received his Master’s degree from the University of Toronto ’s Faculty of Forestry. Justin’s work is motivated by the belief that trees have crucial aesthetic and cultural values, and that their systematic elimination from densely populated urban areas is an avoidable disaster. He can be reached for comment at

All graphics created by Kathleen Morgenroth