Pruning describes the removal of plant parts to manage plant growth. Trees with branches that are well-spaced up the trunk, shrubs with thick, healthy foliage: this is the ideal we all strive for. A few minutes spent pruning is one of the best things you can do for your plants, and the returns are well worth the effort. Pruning techniques vary according to plant species, location and desired results.

When to prune

Trees: Maintenance pruning is usually done in early spring – March or April – before buds appear. Birch and Maple trees, however, should be pruned in late fall after the leaves have fallen. Never remove more than one quarter of live foliage if you are pruning during the growing season.

Shrubs: Plants with decorative leaves such as dogwood or ninebark, and those that bloom on new wood such as hydrangea and potentilla, should be pruned in early spring. Shrubs that bloom on old wood such as lilac, weigela and spirea, should be pruned after the flowering period.

Conifers: If large branches must be removed, prune in the fall to avoid “bleeding” (loss of sap). Pruning younger shoots to obtain a certain shape should be done around the end of June. You should never cut more than half of a conifer’s new growth.

Pruning cuts

Growth definition pruning: establishes good structure for young trees, done in the first years after planting.

Maintenance pruning: is done annually to maintain a desired form or shape and to promote plant health. Encourages flower and fruit development, promotes fuller foliage. Thinning opens the crown to sunlight and air circulation. Excess, dead, weak or gangly branches are removed.

Rejuvenation pruning: involves cutting branches right back to stimulate new growth. Done over more than one season and only as needed.

Lopping: involves cutting off large branches, when necessary.

Fruit-tree pruning: is done annually to encourage fruit production on fruit trees and shrubs.

How to prune

Here are a few simple rules for effective pruning.

Cutting angle: Cut small branches diagonally at a 30º angle about 0.5 cm above the bud and run your cut in the same direction as the bud.

Cutting back a long branch: Use pruning shears or a saw to cut the branch at the branch crotch, where a secondary branch leads out in the same direction as the branch you are cutting, preferably horizontally or along the underside of the branch you are cutting.

Reshaping the central leader: The central leader is the prolongation of the trunk at the summit of a tree. If the leader has been broken, cut it back to a strong side shoot that is growing fairly vertically. Attach a stake to the new leader training it upwards. If there is more than one leader, select the strongest and most in line with the rest of the tree, and remove the others.

Removing a branch at the trunk: Don't cut a branch flush with the trunk. Cut it just above the branch collar. This collar is, in fact, scar growth that will quickly close the cut.

Removing branches 3 cm in diameter or more: Three cuts will be necessary when cutting large branches to avoid tearing the bark:

  1. Make the first cut on the underside of the branch 30 to 40 cm from the trunk, one third to one halfway through the branch.
  2. Make the second cut a few centimeters further out on the branch above the original cut. Saw until the branch brakes free.
  3. Make the final cut just beyond the branch collar. Don’t leave a stub. If the branch collar is left intact, the wound will seal more effectively.

Helpful advice

  • Use the correct tools and keep them sharp.
  • Clean tools after each use to avoid spreading disease.
  • Always wear protective eyewear.
  • Avoid pruning in the rain or if wood is wet in order to prevent disease.
  • Stop often, stand back and evaluate what you have done before you continue.
  • Leave fresh cuts alone so that they dry faster and heal naturally. Plants produce their own enzymes against rot and disease.