Topping trees is an outdated and harmful practice. Where some trees will react better than others, ultimately there will be issues for the tree and homeowner further down the line.
Topping is the practice of reducing a trees height by cutting the leader/s of the tree to a lower height. When a "header cut" is made that is over an inch on a main leader, the tree greatly loses its ability to compartmentalise the wound. This wound will then be left to the elements, where fungus and Bacteria can enter. As Pathogens start to break down the trees tissue rot will set in and start to spread downwards into the main stem.
Side branches or "laterals" will start to assume the role of the removed leader and begin to grow upwards. Lateral branches are designed to hold only the weight of themselves, thus, as these laterals grow upwards weight is put on the union between themselves and where they attach increasing the liklihood of shearing off. This can be clearly seen in the above video.
Trees use capillary action to draw water from the roots to the top of the tree. If the top of the tree is removed it greatly reduces the pressure gradient and retards the waters progress throughout the upper portion of the tree. The open wound at the top of the tree increases evaporation/transpiration leading to wilting.
From a financial stand point, topping is expensive as it locks the client and the tree into an annual maintenance cycle, as an unwanted effect of topping is epicormic growth. Making a header cut in deciduous trees activates dormant buds around the circumference of the cut site, this is an attempt by the tree to grow more leaders. This growth can be prolific, and if left to keep growing can result in multiple, poorly attached leaders.
In the long run, as with the above video, the tree/s may well need to be removed due to them becoming dangerous.
Tree work is a highly specialised job, and a full understanding of species and tree biology is essential to result in safe, effective and healthy trees.
Excelsior tree surgery are based in Glasgow and service the Central belt of Scotland. For free advice and quotes, please get in contact with us.