Trees, when mature, should have a strong straight trunk and a full crown with well spaced branches. Pruning helps achieve this growth pattern.
Visualize what the plant should look like at maturity and prune to maintain this shape. Remember, if you cannot decide whether a branch should be removed, leave it. You can always prune again next year. There are several different pruning cuts you will use:
- Removal cut A removal cut ‘thins out’ a tree and allows more light to penetrate to the center of the tree. When removing an entire branch back to its origin, make your cut just outside the natural branch collar (the slightly thicker area where the branch is attached to another branch or trunk.) The cut should NOT be flush to the originating branch or trunk; however, there should not be a large branch stub either.
- Heading cut A heading cut encourages a fuller, bushier tree or stub by stimulating dormant buds below the cut to emerge and develop new branches. Make your cut anywhere between 2 nodes on a branch.
For additional information about pruning, you may wish to look up 'How to Prune', written by the Forest Service of the US Department of Agriculture.
You will use different pruning schedules depending on the age of your tree:
- Newly planted tree: Only prune dead or broken branches since the tree needs all of its branches and leaves to grown in its new location.
- Year 2: Prune branches to develop a strong central leader. If present, prune and remove co-dominant leader.
- Years 3-4: Begin regular pruning by following the steps below:
- Remove dead, damaged and diseased branches.
- Choose main branches you want to keep and remove the rest. Main branches should be evenly spaced around the tree.
- Remove weak (narrow) crotches, crossed branches, water sprouts and suckers.
- Thin branches to well-spaced, strong main branches, secondary branches and laterals to reduce competition for light, water and nutrients.
- If you wish, remove a few of the lowest branches and leave the rest to help the tree develop taper.
- Years 5-7: By this time, your tree should be healthy and shaped properly from previous pruning. To stay healthy, regularly remove dead or damaged limbs. Keep the tree’s outline tidy by pruning back long branches. If you wish, you can remove bottom limbs if you want to walk underneath the tree.
Special pruning considerations for certain tree species
- Prune deciduous ornamental trees every 3 to 4 years. Prune in the late winter or early spring, when wounds from pruning cuts will close quickly.
- Prune maple and birch trees in June or July to prevent cuts from ‘bleeding’.
- Prune elm trees after the provincial pruning ban is lifted (from September 1 to March 31) to reduce the spread of Dutch Elm Disease.
- Prune apple trees every spring. Light annual pruning balances growth and flower buds.
- Only prune dead, damaged and diseased branches from evergreen trees. In the spring, you can create a denser pine or spruce trees by cutting its candles in half before the needles have elongated. Remember to add a wide circle of mulch around the evergreen’s trunk if you remove its lower branches. The mulch will keep the soil cool around the tree’s feeder roots.