Tree Pruning (Tree Cutting)
Trees are living things, having their own natural defence and maintenance systems. Life, death and decay are all part of this natural cycle and these systems ensure its survival. As time has evolved trees have moved from their natural environment of forests and woodlands and are now put under stresses and strains from unnatural sources, making it more difficult for these systems to work. Most pressures are suffered from man and as a result are adversely affected by such things as root cutting, branch breakage, pollution and most importantly, poor pruning techniques. Natural defects in trees that are not a problem in their natural environment can become a hazard in suburbia. For this reason, trees in our cities and towns require extra maintenance to keep them in a safe and healthy condition. Tree pruning or tree cutting is carried out for a variety of different reasons, not always for the benefit of the tree. Trees or their branches are often considered to be a nuisance or are causing an obstruction. Some tree pruning may be in the interests of tree health, public safety or both. Common terms for these tree pruning operations are crown lifting, crown reduction, crown thinning, deadwooding and pollarding.
All tree pruning cuts cause a wound, opening up the inside of the trunk or branch to harmful pathogens, especially decay forming fungi. The best protection against this the trees own defensive processes. If pruning is carried out correctly such defences are normally effective. Incorrect cuts damage the natural defensive barriers within the wood. It is therefore vitally important that you choose the right contractor to carry out this specialist work, and that all works are carried out to BS 3998: 2010 Tree work – Recommendations.
Below are common terms that refer to different tree pruning operations:
The crown of a tree includes all of its branches. If lower branches are removed, the effect is to raise the crown. Dependant on the size of the tree, this can sometimes be the only remedial work required to allow light infiltration or appeasing neighbours. This type of pruning is often carried out on public highways to ensure passing traffic does not cause damage.
On some species the branch growth within the crown can be dense but by removing small inward growing branches throughout the crown can be very effective. This process can also reduce wind resistance and the overall ‘sail area’ of the crown. If this process is overdone, it can allow long branches to move more independently which could result in breakages during high winds. The overall look of the tree will also be compromised.
A common complaint regarding trees is they are too high. It should be noted that if a tree is in good health and is firmly rooted, the height of a tree does not make it necessarily make it dangerous. If the stability of the tree is in question you should seek advice, and crown reducing or thinning may be an option to alleviate the stress of weaker points. Unfortunately, in some cases it may ne necessary to consider completely removing the tree and replant in mitigation of its loss. For more information regarding tree removal please refer to our Tree Removal and Tree Stump Removal pages. Reductions may also be a consideration for trees that were planted in inappropriate locations for their size, for example, close to buildings, or beneath electricity wires. Generally, the reduction would be over the crowns entirety to maintain its natural shape and form and depending on its species, up to approximately 30%.
Crown reduction is not the same as ‘topping’ or ‘lopping’ (a description of these terms can be found below). Crown reductions are achieved by carefully selecting and cutting back to side branches, to reduce the injury and decay to the tree. Very substantial crown reductions can be detrimental to tree health due to the loss of leaf area and the large wounds created.
Removal of Deadwood (Dead Wooding)
There are a number of reasons why deadwood occurs in trees, and during the demise of the branches they can become host to different pathogens and harmful decay fungus that can eventually spread to other branches or even the main stem of the tree. Eventually these branches will fail which could incur damage to the public or property. Deadwood can occur due to storm, vehicle or other mechanical damage, the natural shading of other branches or commonly through poor tree pruning techniques such as ‘topping’ and ‘lopping’ as long stubs are left without leaves causing die back. For these reasons it is beneficial that dead wood is removed.
Lopping and Topping
These terms are no longer generally used in modern arboriculture and only generally in forestry. The tem ‘topping’ referred to the removal of the upper crown of a tree and ‘lopping’ of side branches. This practice causes significant wounds detrimental to the health of a tree and has now been removed from legislation in the recently revised BS 3998, in favour of the more common and better practice terms of crown thinning and crown reductions.
This is a practice for certain species of tree as it can cause significant wounds. It involves the removal of branches for many reasons for example, preventing trees outgrowing their allotted space, reducing the shade cast by a tree and may be necessary on street trees to prevent electric wires and streetlights being obstructed.
Listed below are a few of the species that pollarding is acceptable:
- Ash (Fraxinus)
- Common lime (Tilia × europaea)
- Elm (Ulmus)
- Elder (Sambucus)
- London plane (Platanus × hispanica)
- Mulberry (Morus)
- Oak (Quercus)
- Some species of Acer (A. negundo and its cultivars)
- Tulip tree (Liriodendron)
Pollarding a tree is generally done on a three year cycle. The practice requires leaving a trunk supporting three or five branches depending on the size of the tree, cut back to a desirable length. As the wood lays down annual growth rings, the union strengthens, often forming a thickened base where the shoot meets the trunk. Over a number of years, a swollen 'pollard head' forms where new shoots grow each year and repollarding would involve cutting back this growth to the pollard head.