There is a hideous practice that has been going on for decades and the entire arborist community is trying to stop it. This sad and damaging trend is the negligent topping of trees! Topping can be referred to as hat racking, stubbing off, shearing or murder. The official definition as put forth by the International Society of Arboriculture is
“The reduction of a tree’s size using heading cuts that shorten
limbs or branches back to a pre-determined crown limit.
Topping is not considered an acceptable pruning practice.”
The reason this practice can be referred to as murder is that once it has been done it marks the beginning of the end for that tree. It starts with starvation. If we think of pruning as being a healthy diet for a tree, topping it would equate to starvation. This makes sense because the leaves that make up the trees canopy are the food factories that keep the tree running. When too much of that canopy is removed the trees ability to produce food is also removed. As soon as this happens the tree biologically panics and stimulates a rush of new growth that is often referred to as water sprouts or suckers.
Unfortunately this new growth is only partially attached to the older wood. This makes the new growth substantially weaker than what was there previously. Add in the trees need to get the canopy back to its original size and you’ve got a math problem. In a few short years those weak branches are just as tall as the ones you had cut back and there are more of them! As those years have progressed the stubs that were left and the stress cracks it produced have opened up a pathway for pathogens and insects to enter the main branches and even trunk wood. These things can go unseen for years while they attack a starving and handicapped tree until it finally fails.
Economically the topping of trees is more costly than correctly pruning or simply removing them. It costs a little more up front to have a certified arborist do the work correctly but it will need to be done about a third as often and will not leave you with a liability in the backyard or along the street that will have to be removed later on. If the tree is absolutely too large for you than its better to look at removal and replacement with a correctly sized tree than reduction. The main key to avoid even thinking of topping as an option is to Plant the Right Tree in the Right Place!!!
Cities all over the country including the city of Idaho Falls have set it out in their city ordinances that only those who at least consult with a Certified Arborist and receive a city permit are allowed to work on specified city trees. They have implemented the ruling to preserve the beauty and value well maintained trees provide to a thriving location by having the work done to follow the Ansi A300 national standard. City trees include the trees in parks and between most curb strips and sidewalks. If you would like to read the exact ordinances you will find it by following the link and then going to Title 8 Chapter 9: http://www.amlegal.com/nxt/gateway.dll/Idaho/idfalls/cityofidahofallsidahocodeofordinances?f=templates$fn=default.htm$3.0$vid=amlegal:idahofalls_id
The Ansi A300 standards are only available through purchase online: one of the sites that offers them is the TCIA website linked here:
http://www.youtube.com/watch?v=HfZawwjcVXw (Anti-topping video)