How to prune old trees to prevent risks

Thanks to the visionary policies of our ancestors, we have the iconic imprint of a city like Buenos Aires, dressed in majestic and unique trees, and among them, legendary old trees. Today we have to take care of their legacy with cultural sensitivity, respect and the technical knowledge they deserve. The trees of the city, […] [supsystic-social-sharing id="1"]

Thanks to the visionary policies of our ancestors, we have the iconic imprint of a city like Buenos Aires, dressed in majestic and unique trees, and among them, legendary old trees. Today we have to take care of their legacy with cultural sensitivity, respect and the technical knowledge they deserve.

The trees of the city, both in private gardens and in public spaces and the road, make up the “urban forest”. Although we all recognize the importance from the cultural and landscape point of view of a green city, it is necessary to highlight its environmental role, essential to mitigate the effects of climate change.

Trees capture carbon dioxide and lower the city’s air temperature, contribute – with their foliage and root systems – to cushion the effects of torrential rains, reduce soil erosion and reduce noise pollution. The trees form a biological corridor that contributes to counteract the decline in biodiversity.

And while it is true that trees have multiple services and benefits, they can also produce conflicts, mainly when the species was not correctly chosen for a given site or when it was poorly managed. If we talk about old trees, the threats can be more serious. From the point of view of risk related to trees, as in most things, zero risk does not exist. Even the safest tree can fail, entirely or partially, in very abnormal weather conditions.

Pruning is, within the set of management practices that can avoid hazards, one of the most important. Pruning accompanies the correct growth and the best development of the tree and is essential for the evolution of the tree and its adaptation to the urban environment. When pruning old trees, a fundamental requirement must be taken into account:

  • Clearly determine what or what the pruning objectives are. Without lawful objectives you can’t talk about pruning.
  • Clearly determine what type of pruning will meet these objectives. Have trained machinery, technicians and operators.
  • Perform periodic removal of dry branches.

Do not prune more than 25% of the total volume of the green tree canopy per intervention, until the specimen recovers its reserves. By removing wood, there is less capacity to store energy and there is loss of structural integrity. The pruning objective must not necessarily be met in an intervention.

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According to internationally recognised concepts in arboriculture, and according to the species, the maximum diameter of branches to be pruned must be between 4 and 10 cm. The elimination of branches of greater diameter is considered an exception and will generate a decrease in the life of the specimen due to the generation of wounds that will result in rot, entry of xylophagous insects, etc.

When assessing safety and lighting problems, it is essential to avoid the eventual irreversible damage or deterioration of the tree due to excessive pruning.

Evaluate the time of pruning according to the physiological and phenological state of each species. Postpone pruning in case of droughts, floods and high temperatures.

In the “urban forest”, the specimens form alignments, galleries, vaults, working as a functional group. If they are extracted or pruned excessively, or the plot is opened, the remaining trees will suffer the onslaught of winds from which they were protected, for which they have not generated biomechanical resistance.

If old trees located on public roads do not receive specific care, they can cause damage. If old trees located on public roads do not receive specific care, they can cause damage.

To keep in mind: the consequences of pruning

  • By eliminating foliage there is lower production of carbohydrates, that is, less photosynthesis.
  • After injuring living tissues, the consumption of carbohydrates increases to protect wounds and emit new outbreaks.
  • By removing wood, there is less capacity to store energy and also loss of structural integrity.

Tips to optimise your tree pruning

Pruning involves totally or partially eliminating dry, dead or poorly oriented branches. A good pruning improves and prevents the health of the tree and also of people and birds that share their surroundings. The improper use of pruning can produce exaggerated growths, since the tree spends a lot of energy growing new branches on the edges of the stumps. To do it the right way, keep in mind that:

-The pruning of only one side of the tree leaves it unbalanced and in danger of falling during storms or wind.

-In pruning structure reduction, you should avoid cutting branches larger than 10 centimeters in diameter.

-In young trees, thinning is a form of pruning where branches are removed from the junction with the trunk, or secondary branches of a main branch. This will help reduce the amount of new offspring and drive tree growth.

Pruning should be done when the tree is in a vegetative period and the sap barely circulates. Poorly made or misplaced cuts cause fungal infections that can cause the tree to rot.

On the other hand, leaving a branch next to the cut allows the sap not to abruptly interrupt its ascending path. That way, rotting and excessive emergency outbreaks are avoided,

How is a proper cut made?

-Before anything, keep in mind that every cut involves a wound. In order for the tree to begin to heal, the cuts must be clean, without tears. For that it is necessary to use sharp tools and make the cut in the right place.

-The cut must be made neither too close to the trunk nor too far away. Precisely at the point of union with the mother branch, or at the intersection of two branches, where a “y” is formed. Try not to make them flush with the trunk.

-The bevel cut is much more suitable so that the wound does not retain moisture. Moisture favors rot and fungal attack. In addition, the neck (area of ​​the base of the branch) must be respected when making the cut, since there they concentrate the cells that will help heal the wound.

-In branches of a large diameter, so that a tear of the bark does not occur, it must be cut in two steps. First a notch is made, it is cut higher and finally, the rest is removed by holding it.

– The risk of rot increases when the cuts exceed 5 cm in diameter, so if you cannot avoid making a large cut should be smoothed and retouched until they are perfect.

Bear in mind that Perth Tree Service is a recognised business that provides specialised mulching services in Perth