Billings, Montana @ ZooMontana
Reasons to Prune
Safety– By removing dead or decaying branches, or trees, can reduce the risk to public safety. Raising the lower branches of a tree near a stop sign or drive way may improve visibility.
Structural Strength– Thinning a tree canopy can allow for more airflow circulation through the crown of the tree, reducing the likelihood of failure during a wind or snow event. Air circulation in the crown also can help confuse pests that might be looking at your tree for a place to make a home. Establishing a central leader and good structural in scaffold branches will set the tree up for success in years to come, saving money in long term maintenance costs.
Health-Removing dead or dying branches can help the tree begin to create callus wood, which seals pruning cuts. The sooner the branch compartmentalizes, a barrier is formed to lessen the chance of invasion by insects and diseases.
Aesthetics– A properly maintained tree is more likely to survive, providing enjoyment for years to come.
Do not prune trees without clearly defined objectives:
Maintain safety (reducing risk of failure)
Improve tree health and structure
Reduce shade and wind resistance
Influence flower and fruit production
Improve a view
Remove water/sucker sprouts (poor attachments)
Though mature trees may need only occasional pruning to remove dead wood, young trees should be pruned regularly to provide strong branch structure for future growth. Select scaffold (central structural) branches that are at least 18” apart and evenly distributed around the trunk. Branches should not grow directly above one another. Maintain a single leader as long as possible.
Pruning cuts should always be made near the base of a branch (Figure 1). Do not leave a stub. When heading back (drop-crotching) a tree to reduce its size, always cut the leader back to a lateral branch large enough to assume the terminal role. The lateral branch will eventually become the new leader. Indiscriminately sawing-off large branches (topping) is not acceptable. The new branches produced on the stubs are very weak.
Large branches are removed with a 3 step process (Figure 2). First, cut partially (no more than 1/3) through the branch from the underside. The second cut is made through the branch from the upperside a short distance beyond the first. The third and final cut is the most critical. This final cut is made where the branch arises from the trunk at the swelling called the branch collar. The final cut should not be made flush with the trunk. This results in a very large wound and a greater possibility for poor healing and the introduction of decay.
The best time to prune is between mid-February and early May. Trees pruned at this time in early spring develop a callous around the cut much more rapidly than those pruned at other times. However, there are a few exceptions to this rule.
Maples, walnuts, birches, beeches, hornbeams, and yellowwood are known as “bleeders”. The “bleeding” may be unsightly, but it does not harm the tree. Bleeding results from copious sap flow, and can be avoided by delaying pruning until after the foliage has fully emerged.
Spring flowering trees should be pruned after flowers have dropped.
To avoid the introduction of disease pathogens to oaks and elms, avoid pruning between April 15 and October 15.
Prompt pruning of storm-damaged limbs and dead branches should be done to encourage wound closure and avoid potential hazards.
Pruning of dead or immature branches can be done almost anytime. Dormancy is the best season with the least amount of impact on the living portion of the tree.
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