Considering Pruning

The first question, when considering pruning, is whether cutting off and removing living branches will actually benefit the tree? Will the proposed pruning prolong it’s useful life expectancy within the context of the surrounding environment and land use? It is important to remember that pruning may do more harm than good, and in some situations may create more problems than it solves. Why does the tree need pruning, in fact does it ‘need’ to be pruned?

Every cut made has the potential to change the growth characteristics of the tree. Removing living foliage, by pruning, affects the trees physiology and future productivity. The reduction in leaf area that results from pruning will reduce the tree’s overall photosynthetic capacity and may reduce overall growth on the pruned section, or the entire tree. Pruning can therefore have a lasting impact on the viability of the tree and can directly influence it’s longevity.

One of the major limitations of crown pruning is that it has a very one-sided impact on tree physiology. Before pruning the tree will be maintaining a natural equilibrium of growth, both in the crown of leaves and branches, and underground in it’s system of roots. Raw materials are absorbed from the soil, moved up through the transport system within the trunk and branches to the leaves, where energy is produced through photosynthesis. By removing leaves and branches from the crown the arborist disrupts the balance, forcing the tree into a state of turmoil.

Trees are one of the few organisms which have an average life expectancy that exceeds our own (human) ‘three score years and ten’, yet we offer them very little respect for this achievement. In fact, trees figure so low on the day to day agenda of modern life that few people stop to consider their value. However, when someone actually pauses to think of the contribution trees make to their lives as an individual, or as a member of society, the list can appear endless.

There is a growing recognition that trees have a part to play, from the calming influence they have on our everyday lives to their ability to sequester carbon-dioxide which could influence the sustainability of human survival on the planet. Many of these beneficial attributes are linked to the slow progression of tree growth over their long life spans, which can frequently be measured in centuries. However, many trees are deprived of the opportunity to live out their natural lives, because of a human ignorance that inflicts it’s will on the world with an arrogance that fails to recognise that everything is intrinsically connected.

The technological advancement of human society has created populations of people who have lost track of their cultural connection with an area or community, to the extent that they shuffle around their country and sometimes the world, moving from place to place. Is it any surprise then, that the new owner of a suburban residence has no qualms with felling an oak tree, which may have been planted over 100 years ago during an era he/she feels no connection with?

The person who fells the 100 year old oak, fails to appreciate it’s value and considers that his/her rights, to live in a place without trees, are greater than the accumulative values and benefits of the one oak. However, the same person may only live in the property for no more than a decade, less than a tenth of the trees age. Which of the two has, earned or deserves, the greatest right to life?

“Generations pass while some trees stand, and old families last not three oaks.”
Sir Thomas Brown

Learning the Compromise

In this over populated modern world there have to be compromises to maintain some degree of harmony, and if we are to life in association with trees the compromise is pruning. There is rarely space in our crowded towns, cities and even villages, for the mature size of trees. Some form of pruning has to be considered to readdress the balance, but just because they are perceived to be growing in the ‘wrong’ place, does that mean they have lost their value?

A tree may be deemed to require pruning because it is considered to be ‘too big’, a ‘hazard’ or simply growing in a location where it is at odds, or out of context, with the surrounding land use. However, there is no reason to ignore it’s potential life expectancy, and the ecological values associated with it. Pruning work must be completed with an understanding of the physiological limitations that impact on the tree’s ability to react to the loss of living foliage. Pruning is all about compromise!

The reactive capacity of a tree will be compromised to some degree, depending on the pruning techniques employed, and the volume of living wood and foliage which is removed at any one time. When making pruning decisions the arborist must consider the chronological age of the tree, because a tree in it’s formative years may be able to tolerate the loss of a large limb, but the same tree in full to late maturity might suffer terminally in similar circumstances.

An arborist who is responsible for large populations of trees, such as those owned and managed by local authorities or large parks and gardens, must guard against the use of generic pruning specifications which do not take the trees chronological age into consideration. It is also essential that the same arborist’s keep records of tree populations, and how they have been managed. Because during their working life, of up to 55 years, they may have influence for less than 25, which is a quarter of the life span of a 100 year old tree.

“I resent the creation of a world in which beauty is a reminder of what we’re losing,
rather than a celebration of what we’ve got.”
Ben Elton

It is well established now, through the work of researchers like Lonsdale, Schwarze, Boddy and Raynor that many plant pathogens co-exist for extended periods of time, in harmony with their host. Although the full significance of this has yet to be interpreted from the observational research completed to date. The concept that the organisms we consider to be pathogens (and therefore ‘bad’) make some positive contribution to the arboreal ecosystem, does not require a ‘leap of faith’ or great foresight. However, it is equally important that we do not jump to conclusions.

Thoughtless pruning can interfere with and interrupt the natural balance between symbiotic and parasitic relationships within the tree and associated arboreal ecosystems. The physiological, pathological and ecological impacts of pruning work will not be immediately apparent, because the tree will react through growth which occurs over a period of years.

A greater understanding and appreciation of the long life processes of trees is essential. An arborist responsible for the care of just one tree, can only hope to have an influence for a fraction of it’s potential life span. However the pruning decisions, that the arborist makes, can have a direct impact on the tree and it’s sustainable life expectancy. A decision made today could have consequences that are experienced decades and possibly centuries after.

Trees, as long lived organisms, are slow to react to changes in their environment. Our increasingly fast pace of life means that we can inflict change on our surroundings in quick succession. A tree, which may fall victim to this, will suffer stresses that could culminate in premature death.

“If we represent knowledge as a tree, we know that things that are divided
are yet connected. We know that to observe the divisions and
ignore the connections is to destroy the tree.”
- Wendell Berry -