Pruning

It’s June and we should all be outdoors enjoying the trees and shrubs in our yards. This time of year also brings out the tree crews offering to prune your trees. Here are some things to keep in mind before you have anyone touch the trees on your property. Pruning is the most common practice we do as tree care professionals and also one of the most important. An arborist will prune a tree for health, safety and appearance, but also to reduce disease pressure or provide clearance for a view.

The most common type of pruning on younger trees is crown thinning – the removal of live, healthy branches on trees with dense crowns.  This improves light penetration and air movement and reducing pest infestations and decreasing the risk of storm damage. Thinning can also be used to reduce weight of individual limbs and to slow the growth rate on overly vigorous limbs. On slower growing mature trees, thinning is mainly used when weight reduction is needed on individual limbs to compensate for structural defects.

Virtually all urban trees benefit from periodic crown cleaning – the removal of defective limbs including those that are dead, dying, diseased, rubbing, and structurally unsound. Cleaning reduces the risk of branch failures, improves plant health and enhances tree appearance by removing limbs that are unsightly, unhealthy and unsound. Although removal of healthy branches is technically “thinning”, selective removal of watersprouts is included in a crown cleaning. But before removing watersprouts, arborists must judge whether sprout removal will benefit the tree. Stripping sprouts is rarely beneficial and may eventually create many more problems for the tree. An arborist should look for the cause of watersprout production in a tree. A tree often creates sprouts in response to an injury or disease. If watersprouts must be pruned they should be removed over the course of a few years.

Crown reduction is needed on trees or individual limbs that are growing close to buildings, other trees, or utility wires.  Reduction may also be necessary to prevent or correct storm damage and to shorten errant branches to provide a more desirable shape. This type of pruning involves reducing the height or spread of the crown or individual limbs.  Certain species such as beech and sugar maple respond poorly to reductions so consideration must be given to the ability of the species to tolerate this procedure.

Crown raising is done when lower limbs interfere with mowing, traffic, people or utilities. Limbs can either be removed at the trunk or downward growing branches can be removed at the parent limb.  Thinning the ends of a heavy limb may accomplish the same goal if the limb rises when weight is removed. When raising is performed, limb levels generally are left at a uniform height around the tree to provide symmetry.

The majority of established trees can benefit from one or more maintenance pruning types.  How can you prune a tree in more than one way?  Easy!  If a tree is growing next to a house and has deadwood and limbs rubbing against the roof, it needs crown cleaning throughout and reduction or raising of the limbs over the residence.

Finally, arborists and homeowners must realize that more is not always better when it comes to pruning. The amount of foliage that should be pruned from mature trees is often less than what clients expect. The Standard in the industry instructs that not more than one quarter of the leaf surface be removed during a single pruning operation. This will benefit the tree by maintaining a greater leaf surface area for conducting photosynthesis.

 

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