Tree Management

The Need for Maintenance - Why should a tree need to be maintained?

Unlike cars or houses which need regular repair, trees are living things, having their own natural defence and maintenance systems. Life, death and decay are part of the natural cycle of life, and this includes trees.

In forests and woodlands trees compete with each other and with many other living things for light, space, water and energy. The defence and maintenance system within the tree ensures its survival. In the forest, lower branches die and are shed, and the trees develop long slender trunks. Weaker trees may die, fall down and decay. Storms may cause branches to break off and fall to the woodland floor, to decay and become hosts to many other organisms. Dead branches and cavities can be important wildlife habitats for many species.

However, trees have been brought out of the forest and into the urban environment where we live and work, or where the encroachment of roads and buildings into the countryside has altered their natural environment.

Trees in urban areas have to live in an alien environment with soil conditions that lack the natural balance of water and nutrient supply required for normal growth. They have to compete for space, tolerate pollution from vehicles, poisoning from chemicals such as de-icing salt, and wounding by pruning requirements.

All this in addition to coping with natural threats such as viruses, fungi, insects, mammals, birds, severe weather and other agents which damage trees. It is a miracle that trees even manage to survive!

Natural defects in trees and damage due to adverse weather that are not a problem in the forest can be a hazard in the urban environment. For these reasons trees in parks, gardens, streets and public spaces require extra maintenance to remove hazards and minimise the risk of harm to people and property. The extra maintenance is often called 'tree surgery'. There is both a personal and public interest in keeping our trees healthy and long lived. The proper care of trees with an understanding of how they grow and defend themselves is called 'Arboriculture'.

Tree work - Pruning

Pruning is carried out for a variety of reasons, not always for the benefit of the tree. Branches are often considered to be a nuisance or are causing an obstruction. Some pruning may be in the interest of tree health, public safety or both.

Trees should not be pruned if it is not necessary to do so since any cutting can weaken a tree and each pruning wound exposes vulnerable tissues, which may be invaded by wood decaying organisms. Pruning of a healthy tree usually results in the production of vigorous new growth which depletes the tree's food reserves. In certain species the harder the pruning then the more vigorous the new growth, commonly referred to as epicormic growth, will be. Older trees do not tolerate pruning as well as younger ones and substantial pruning can be very damaging, particularly in species which are not naturally tolerant of cutting.

Very substantial reductions can be detrimental to tree health, because of the loss of leaf area and the large wounds created.

Pruning operations

Generally most trees that need to be pruned will require one, or a combination of the following pruning techniques.

Pruning should aim to remove no more than 15 - 20 % of the crown at any one time.

Pruning aims to develop a strong and well balanced branch structure.

Crown Thinning This is the removal of a small portion of the secondary and small live branches throughout the crown. Thinning should produce a uniform density of foliage around an evenly spaced branch structure and reduces the density of the crown without altering the shape and form of the tree. Thinning allows more light to pass through the crown, reduces wind resistance and can lessen the weight of heavy branches. Crown thinning includes crown cleaning - the removal of dead, dying, diseased, crossing, crowded and weakly attached branches of low vigour.

Crown Lifting This is the removal of the lowest branches and preparing of lower branches for future removal. Crown lifting should avoid creating large wounds on the main trunk of older trees as these may take many years to heal. To avoid lack of balance after crown lifting the crown should be at least 2/3 of the total height of the tree. Useful for allowing more light into a property. Provides clearance above roads, footpaths and smaller out buildings, such as sheds and garages.

Crown Reduction This is the reduction of the crown of a tree, or the tree itself, whilst maintaining its natural shape and form as far as practicable. The ends of the branches should be removed back to a suitable growing point (i.e. internal lateral branches) and the diameter of the remaining branch should be at least 1/3 of the diameter of the branch that is removed. Ideal for preventing branches contacting buildings, roofs and gutters. Removal of branches obstructing street lighting, overhead cables, signs and other infrastructure.