Maintenance Pruning - Deciduous Trees

WHY PRUNE:

Maintenance pruning of shelterbelts is practised for three main reasons. Dead, diseased or storm damaged branches are removed for reasons of safety, appearance, and disease control. Secondly, branches that interfere with powerlines, machinery operations or pose a threat to property need to be removed. Finally pruning is carried out to improve the appearance of the shelterbelt by removing suckers and interfering or wide-spreading branches. However, unlike shade trees which are pruned up to accent their form, in shelterbelts the removal of lower branches should be done only if there is a need to change the density of the windbreak.

WHEN TO PRUNE:

The recommended time for pruning is during the winter or early spring in order to lessen the damage of infection. However, in practice it may be more desirable to prune in mid-summer when the trees are in full leaf in order to easily locate dead limbs or branches lacking in vigour. Mid-summer is also the best time to prune trees such as maple and birch. When pruned in spring these species may lose excessive amounts of sap. However, pruning should not be done too late in the fall as wounds will not have a chance to heal before winter. Pruning of dead branches can be done at any time of the year since no living tissue is affected.

HOW TO PRUNE:

In pruning, appraise the tree before cutting in order to select the branches that will serve as the main structure of the tree. Make all cuts close to and parallel to the trunk or crotch.

When pruning diseased parts, remove 15 cm or more below any evidence of the disease which usually means going back to a living lateral branch or to the trunk of the tree. In order to avoid damage to the main limb or trunk when cutting large branches, use the 3-step cutting method. The first cut is made part way through the branch on the underside a short distance from the limb or trunk to which it is attached. The second cut is then made from the top down 2-3 inches further out on the branch. the weight of the branch will cause it to break free and fall outwards without tearing any bark. The third and final cut is then made reasonably flush with the limb or trunk in order to avoid leaving a stub. At the same time it is important to avoid cutting into the limb or trunk. Leaving a minimum of exposed surface will allow the cut to heal over in time.

When removing dead branches avoid cutting into the callus tissue which has formed at the base of the branch so that living tissue is not exposed.

In order to make sharp, clean cuts, ensure that tools are in good condition. When removing diseased material, tools should be disinfected in a javex or alcohol solution between each cut.

The treatment of tree wounds with dressings is a contested subject. While dressings protect against invasion of water, diseases and insects, they also impede the healing process. If they are used, obtain one of several commercial products. Do not use ordinary paints.

SUMMARY:

Maintenance pruning should be done such that the natural form of the tree is followed or restored while removing all dead, diseased, broken and crossed branches. In order to maintain shelterbelt density at all levels, remove only what is required. In any case, never remove more than 25% of the producing potential of the tree in any one season.

CAUTION:

Contact the power company to attend to branches interfering with powerlines.