A question we asked from time to time at Tree Care Auckland is “will you be painting the wounds after pruning?” The purpose of this Blog post is to explain why we do not paint tree wounds and instead leave them open to the environment. In theory painting over a freshly cut wound on a tree seems like a good idea. There was no gap in the protective layer of the bark before pruning so surely reinstating a new one would help the tree. In reality painting over a tree wound can either have no effect at all or can actually increase the rate of decay and restrict the tree’s ability to callous over the wound itself. Our expert advice is do not paint tree wounds.
Do not paint tree wounds after pruning trees
Trees have been shedding and losing branches for as long as there have been trees, which, depending on your source, could be as long as 360 million years . That’s a long time; long enough for trees to have developed their own coping mechanisms. When a tree loses a branch it responds both internally and externally to re-fortify its defences. On the inside, chemical barriers are formed to ward off any attacks from pathogens. On the outside, the tree begins to grow reactionary wood which will eventually callous over the wound, increasing its strength and creating a physical barrier to entry. These processes are governed by the tree and occur at a rate which is in balance with the rest of the tree’s processes.
Pathogens, or agents that can cause disease in trees, are abundant in the environment.
The tree is exposed to them all the time. The spores (similar to seeds) of fungal pathogens are microscopic and float around in the air. As soon as a branch is cut these spores will be landing on it. A healthy tree is able to ward off attacks from most pathogens. When a wound is painted to create a barrier it is likely that spores will already be inside the wound. Research has shown that painting can actually have the reverse of the desired affect; an environment that favours the pathogen over the tree can be developed increasing the rate of decay.
So, if we are not painting wounds after we cut them what can be done to limit the risks of decay following pruning? The first step that can be taken is to limit the size of the wounds themselves. Smaller diameter branches are more dynamic in their recovery and heal over more rapidly. Also, pruning trees well when they are young reduces the need of them being pruned in the future. Another step is to sterilise tools between jobs or trees.
An expert arborist will advise you do not paint tree wounds
At Tree Care Auckland we clean our cutting tools with a disinfectant at the start of each job to prevent cross contamination from one tree to another. Finally, by ensuring the tree is kept healthy it will have a greater chance of success with its own natural defences. Improving the growing conditions around the base of the tree with aged wood mulch has a variety of benefits and is a simple and effective way to give your tree a helping hand.
For more information see the following articles:
- Wound Dressings
- Benefits of mulching trees