Basic Tree Pruning

Why do We Prune?

  • Remove broken, dying or diseased branches
  • Encourage new growth and tree vigour
  • To either increase or decrease fruit production
  • Aesthetics and tree shaping

Pruning large trees or trees near power lines requires the attention of a professional arborist. For tips on finding an arborist, see our Find an Arborist page. If you decide to prune the trees yourself, here are some helpful tips:

  • Prune all dead or dying branches on a regular basis to improve the tree’s health and avoid future problems.
  • Prune to maintain the desired shape or size and to keep the tree attractive.
  • Prune crossing or rubbing branches to avoid further damage.
  • Prune to increase or reduce density of the tree.
  • Generally trees should be thinned to produce a more open plant allowing light and air to penetrate to the canopy interior.  However, if denser growth is desired, heading back is required.
  • Whether you prune your trees yourself or have the work done by a contractor, it is essential that all pruning equipment be disinfected prior to and during pruning.  Disinfection with 50:50 methyl hydrate and water helps to prevent the accidental spread of disease to other trees.

 

The Perfect Pruning Cut

The point on the stem or trunk where a branch is attached is called the branch ridge and collar. This is also where the “healing tissue” is found, and if a branch is pruned properly, the tree will heal over the wound by itself. It’s important not to cut too close to this tissue or too far away; doing so will result in improper healing and will leave the wound open to pests and disease. Generally, pruning cuts should be made at a 45 degree angle to avoid damaging the branch ridge and collar.

Types of Pruning

Crown Thinning

Thinning is the removal of whole branches where they attach to the next major branch or the trunk of the tree.  This process is used to remove weak, aged, dead, diseased or undesirable branches.  Avoid removing large branches which will take away more than one-third of the tree’s total growth.

 

Heading Back

Heading or cutting back of a stem or branch just before the bud, can help maintain the shape or height of a tree.  If done properly, it can also be very helpful in eliminating several types of growth problems. Heading back is often done at transplanting time.  Some deciduous trees can benefit from pruning when transplanted to compensate for roots lost during the process.  Heading back during transplanting allows your tree to open up and develop strong, sturdy new growth. Use the “one-third formula” when heading back.  Never remove more than one-third of a live branch.  As well, avoid removing large branches which will take away more than one-third of the tree’s total growth.

 

Large Limb Removal

Removing heavy limbs, 7 cm (3 in) in diameter or greater requires certain precautions to avoid tearing bark from the tree trunk.  The first cut into the branch is made on the lower side, about 30 cm (12 in) from the trunk. The second cut is made on the upper side of the branch; about 35 cm (14 in) from the trunk. Finally, the remaining stub is cut off, while keeping the branch ridge and collar intact. This method ensures a clean cut that will heal over properly.

 

Treating Wounds

Ensuring a proper pruning job will speed the healing process of the tree. Trees have their own defence mechanisms and will heal the pruning wound on their own so long as the reproductive cells in the ridge and collar are not damaged. Trees are usually painted for aesthetic reasons, but painting will not speed the healing process as is commonly thought. Household paints and wood preservatives are toxic, and should not be used.