The above image demonstrates what is known as a ‘flush cut,’ which is essentially a term which describes cutting beyond the natural target of the trunk branch union, and into the trunk. This type of cut circumvents a tree’s natural defences and exposes trunk tissue, rather than just branch tissue.
Poor pruning practice such as this will expose the trunk to the potential ingress of opportunistic pathogens, weaken the trunk structurally and deplete finite resources as the tree will try to compartmentalise this wound. In the image above we can see signs of insect attack as well; the round black holes at the bottom of the flush cut are evidence of a wood boring insect, and so is the ‘frass’ or insect excretion located above and to the right of the flush cut.
Unlike animals, trees are not able to heal; by heal I mean repair or replace (in situ) damaged cells. Instead trees spend resources to compartmentalise, or seal, wounded tissue away from other tissue to prevent the further spread of decay. They can also lay down new tissue to improve structure and resist static and dynamic loading. Laying down new tissue is how they grow – essentially replacing the ‘old tree’ with a ‘new tree’ on the outside each year.
In conclusion, flush cutting or poor pruning practices as pictured above can inhibit a tree’s natural defences, waste finite resources, increase the likelihood of decay causing pathogens and ultimately reduce the useful life expectancy of the tree. Always ensure that you engage a cert III or higher qualified arborist to prune your trees!
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