Proper Tree Pruning and Practical Application
The term “proper pruning” means having due concern for the selection and use of correct pruning methods and their appropriate application. The skilled use of a suitable procedure and constraining the quantity of leaf area removed from the tree attempts to maintain an adequate balance between the trees ability to function and the trees form or amount of size control attainable. The most important recognition is to ensure that your trees are consistently pruned properly, no matter what stage of the year, as over pruning trees or poor pruning technique will create more significant tree health issues.
Guidance for Seasonal Pruning
These are general guidelines to prompt the correct timing of various pruning techniques for differing categories of trees given their common phenology and should not be arbitrarily applied without proper consultation to consider the intent of the work.
Late Winter to Early Spring
Evergreen conifers: Typically, these trees will suffer less growth setback if they are pruned or trimmed at this time of the year. This timing is considered a preferable time to control size and maintain shape of ornamental conifers and hedges before the onset of their spring growth.
Deciduous Broadleaf trees: Normally, the pruning of these trees should be avoided if possible once bud swelling has started through till the leaf has fully set on the tree. Doing this helps avoid problems that may arise from excessive sap flow from pruning wounds, redirection of energy resources to wound defence and unnecessary damage to developing new growth.
Spring & Early Summer
Evergreen Broadleaf trees: Generally, a lot of these are best pruned or trimmed during spring to take advantage of the new flush of growth, which helps support the re-distribution of the foliage through their crowns and replenishment of canopy density. Attention needs to be given to flowering periods of specific species and the pruning should be undertaken after their bloom has finished. This will mean that some species, like the Pohutakawa, are best pruned or trimmed later in the year.
Deciduous Broadleaf trees: Once the leaf crown has set (fully opened) properly most deciduous trees can be pruned, with an exception for trees that flower before they leaf (Elm, Cherry, Cercis etc) which are ideally left till the next period.
Palms: Work on Palms is typically the removal of dead or older fronds to lift and tidy their crowns it is best performed during this period to encourage the production of new fronds.
Mid-Summer to Early Autumn
Deciduous Broadleaf Trees: There are certain methods of pruning for these types of trees that is best done when they are in full canopy. This includes removing deadwood, minor crown reduction and canopy thinning work to control foliage distribution and improve sunlight penetration. Also, branch canopy end-weight problems are more easily assessed and better judgements can be made on the amount of reduction needed to address these types of crown stability issues.
Formal Hedges and Topiaries: These will also require a couple of light trims during summer to tidy up the new growth and define the tree back to the desired form.
Evergreen Broadleaf trees: As stated earlier, those trees that have spring or early summer flowering are best pruned or trimmed at this time of year following their blossoming.
Mid-Autumn to Mid-Winter
Deciduous Trees: This time of year, is the best time if any major crown reduction and restructure pruning is required with these trees due to the dormant stage of their above ground structure.
Deciduous Fruit Trees: The pruning of these fruit trees also needs to be undertaken once their fruit has been harvested, this work is typically reduction and thinning of the crown to maximise fruit production, so correct timing is more critical.
Seasonal Pruning Techniques
Crown Cleaning & Dead wooding: This is the removal of dead, dying, diseased, broken, and weakly attached shoots or regrowth from the trees crown. This procedure is best done during summer or early autumn when the tree is in full leaf.
Crown Thinning: This is the selective removal of branches to increase light penetration, air movement and to decrease branch end weight. The removal of all inner canopy branching (known as lions-tailing) is poor practice, rather proper thinning work should focus on improving foliage distribution through light pruning to reduce the outer canopy density.
Autumn & Winter Pruning
Crown Reduction: This pruning technique generally involves a more significant reduction of the trees outer crown back to suitable inner branch structure to reduce its overall size, whilst maintaining natural crown form and structure. This kind of procedure can become an ongoing task and the individual species tolerance to frequent crown reduction varies greatly, therefore its continuing use requires discretion and more frequent lighter reduction thinning is typically a better follow up practice.
Crown Lifting or Raising: This method is the removal of selected lower branches to increase the clearance underneath the trees crown. The removal of significant lower scaffold limbs should be avoided, if possible, to prevent multiple trunk pruning wounds. The removal of smaller lower trunk branches and sub-ordinate branching can usually achieve the desired result without the loss of significant tree structure.
Crown Restructuring: This type of work involves significant alteration to the trees structure and configuration of its crown. Restructure pruning should be considered a one-off adjustment to the trees form, most likely some lighter follow-up procedures will be required to re-establish a natural crown shape.
Crown Restoration: These techniques endeavour to restore a more natural tree form to previously topped, poorly pruned, or severely storm damaged trees. It usually involves the use of most, if not all the above methods to set-up a stable crown configuration.
Pollarding, Espalier, and other types of Short Pruning: These techniques are annual pruning methods that remove the current years growth back to an established framework to maintain an artificial form.
Hedge trimming, Tipping and Pinching: This is a removal of the branch growth tip through shearing, trimming, or pruning. It is required maintenance work on established screening or formal ornamental trees and shrubs. Heavier pruning to re-establish overgrown hedges or ornamentals is reduction work as described earlier, which is best done during winter.