Pruning Mature Trees
This will help you understand mature trees and the proper pruning procedures that they require.
Pruning is the most common form of tree maintenance. Whilst forest trees grow very well left to their own devices, trees in populated areas require regular maintenance of their structure and aesthetics. Improper pruning can cause lasting damage and shorten the life of the tree, therefore it is vital that proper pruning techniques are understood.
Pruning For a Reason
Every cut made has the potential to change the future shape of a tree so there should be a reason for every branch removed. The usual reasons for pruning a tree are to remove dead branches, to improve shape, reduce size and to reduce risk. Trees can also be pruned to increase light to the surrounding area.
Pruning is not necessary to improve the health of a tree. Trees use their dense crown of leaves to photosynthesise and manufacture the sugar they use for their growth and development. Unnecessary removal of foliage can reduce growth and stored energy reserves and can be a significant source of stress for the tree leading to health problems.
When Should I Prune?
Normal pruning work to remove broken, diseased or dead limbs can be carried out at any time during the year with no ill effects on the tree. Generally growth and wound closure can be helped if pruning takes place before new growth in the spring. Trees such as maples, walnuts and birches, will often “bleed” if pruned after the start of spring. It doesn’t look attractive but will usually have little effect on the tree.
Heavy pruning of live branches just after the new growth of spring is not desirable, especially when trees are weak. Around springtime trees have recently used a large amount of their energy to produce foliage and new shoots. Removal of large amounts of foliage and branches at this time can cause stress to the tree and should be avoided.
Placement of pruning cuts are vital to a tree’s growth and wound closure. Pruning cuts should be made just outside the branch collar to avoid damaging the trunk and to allow the cut to heal properly. Be sure not to cut the collar. Poor pruning cuts can lead to permanent damage and unseen internal decay. When a larger branch must be shortened, it should be pruned back to a secondary branch or a bud. When cuts made inappropriately between buds or branches they may lead to stem decay and misdirected growth.
When removing a larger limb its weight should be reduced beforehand. This is achieved by making an undercut around a foot from the limb’s point of attachment to the main stem. Then make a second cut from the top a few inches farther out. This act removes the limb, avoids bark tear, and leaves a stub which can be tidied up and cut back to the branch collar.
Certain types of pruning may be necessary to maintain a mature tree in its current safe, healthy and attractive state.
‘Cleaning’ is the removal of dead, dying, diseased, and broken branches from a tree.
‘Thinning’ is the removal of selected branch to improve tree structure and to increase light penetration through the trees crown. When done properly thinning opens up the crown of a tree, reduces the weight of foliage and smaller branches on heavy limbs, whilst retaining the tree’s natural shape.
‘Raising’ means removing the lower branches from a tree to provide clearance usually for vehicles and pedestrians.
‘Reduction’ like it sounds, reduces the size of a tree. Reducing a tree is preferably accomplished by pruning back the leading branches back to secondarytype of reduction helps maintain the shape and integrity of the tree.
How Much Is It Ok To Prune?
The quantity of branches that should be removed depends on the tree’s size, shape and species, as well as the reasons pruning. When trees are younger they can cope with the removal of a higher percentage of mass better than mature trees do. Usually, no more than 30% of the crown should be removed in one season, and even less for mature trees.
Removing even a single, large-diameter limb can result in significant canopy loss and can create a wound that the tree may not be able to close. Care should be taken to achieve pruning objectives while minimizing live branch loss and wound size.
Dressing wounds is now an old fashioned concept and research has now shown that wound dressings do not reduce decay or aid the closure of a wound. Most arborists will recommend that wound dressings should not be used.