Good Tree Pruning Techniques
Pruning trees is a skill and a very important one to learn because if you do it incorrectly, you can severely limit the life of the tree. Trees are magnificent and a little understanding their biology will help you manage them properly. Trees can not heal themselves as we do when we cut our skin. When a tree is wounded, the tissue does not repair itself, it does not heal, instead the trees reaction is to seal the wound. Two things happen, the damaged area is compartmentalised and a barrier zone is created around the wound. Trees do not heal from the inside, rather callus tissue forms on the outside at the edges of the wound and the new wood eventually grows over, sealing it off from pathogens.
Pruning trees is dangerous especially if you are pruning high up. Realistically, tree pruning is for the qualified arborists who are trained people who manage and understand how to prune trees correctly. They know how to handle their equipment properly and how to climb trees safely. For any pruning jobs above your head, I suggest you hire an arborist. If you do do it yourself make sure your ladder is firmly attached to the ground and you do not take risks. Chain saws should only be used by qualified arborists. They are very very dangerous in the hands of amateurs.
There are many cow boys out there, so beware of people claiming to be tree surgeons. When you are engaging an arborist ask to see their qualifications, if they have personal and property insurance and whether they understand the Branch Bark Ridge (BBR) technique. If they look at you blankly on third question, DO NOT HIRE THEM! It is the correct technique used today for pruning branches off trees.
The Collar Method If you are going to prune a branch off a tree, the first thing you do is try and locate the collar. It is a swelling near the base of the branch near where the branch joins the trunk. Sometimes they are subtle and very hard to find. It is the point where a trees will naturally shed a limb from. If you find it, use it as a guide to prune off the branch. YOU NEVER CUT INTO THE COLLAR, instead you use it as guide. With your pruning saw you remove the branch following the line of the collar about 5 - 10cm (1/2 an inch) away from it. Don't worry if you can't find it, because you can use the BBR method to remove the limb.
The Branch Bark Ridge Method (BBR) The BBR is the tissue, which separates the branch from the main stem and it forms what I call wrinkles between the branch and the trunk. All trees have a collar but with some species like Magnolia grandiflora the BBR is really easy to find, whereas others like Eucalypts sp. are really hard to find. When you find the BBR, work out a 45 degree away from the BBR and that is the spot where you start cutting. It takes a little practice to start recognising these points, but once you get the hang of it, you will never do a bad pruning job again. You will also notice that the final pruning cut looks right and the job is finished. Another thing you will start noticing is all the bad pruning jobs around. You will be amazed and surprised at how forgiving trees are.
How to remove the branch safely Remove most of the branch, leaving about 1/2 meter stub Note: Becareful - branches can be really really heavy Located the collar or BBR Undercut the branch, so that you don't tear the bark when you are doing the final cut Final cut, remove the rest of the branch
Tools of Trade When you are pruning you need a good clean and sharp pair of secateurs. If yours are old rusty and blunt, treat your self to a new pair and the same goes with pruning saws. Pruning saws can not be re-sharpened so if yours is over 3 years old, it is time to get a new one. It is also a good idea every six months to sterilise your pruning tools with some bleach or methylated spirits. This kills all the nasty pathogens that can be spread through dirty tools.
Bad Pruning Cuts Bad Pruning cuts can shorten a tree's life dramatically. Pathogens such as fungi, bacteria and timber eating insects can enter wounds and over time cause decay of the branch which can spread eventually through the entire tree. This is okay in the bush and is vital in the ecology of the environment. It provides homes for birds, possums and lots of other creatures. But in the cities, where people live closely together, trees weakened by bad pathogens can be dangerous and may need to be removed. Trees shows signs of distress very very slowly and we call this tree time. Where you and I bleed immediately and know we are hurt, trees may not show signs they are damaged for many many years. A bad pruning cut today may not have any effect for years, but it has turned a perfectly healthy specimen into a potentially dangerous tree, that needs to be removed prematurely.
Branch attachment How the branches are attached is really really important because if they are poorly attached they can easily fall off and damage your house, roof or you. There are two types of attachments - the U and V. The U shape is a good branch attachment and means they are structurally sound and well enmeshed into the structure of the trunk. A V attachment is not a good attachment and is structurally unsound. Bark and moisture gets trapped in the V and this starts up a beautiful environment for fungi, bacterial and insects to start decomposing the wood, thus making the V prone to splitting. This is called included bark and if you start looking up into the trees, you will begin to notice this.
Sources: http://www.72tree.com/services.html http://ezinearticles.com/?Good-Tree-PruningTechniques&id=6016233