Today we will discuss the practice of topping. Here in the South topping a tree is a common and accepted practice thought to make the tree safer and less prone to breaking. In theory this seems to work but upon further examination we begin to see just how destructive and costly it truly is. Traditionally when a tree has the top removed from it, the branches are cut indiscriminately to form numerous stubs. The customer sees that the tree has had a drastic amount of height and weight removed and is happy with the immediate result. However the true damage is not immediately felt (unless an unqualified "tree company" had been hired and dropped a limb on the house, then the damage is most definitely felt).
When a tree has its branches cut (which hold all of its leafs i.e. food factories) to form a stub, its food producing functions have been removed. This throws the tree into a starvation mode. Once in starvation mode the tree begins to release dormant bud growths, in the form of numerous new shoots, to compensate for the loss of leafs. Most of these new shoots are located at the end of each freshly cut stub. Now where a once healthy limb was, many quickly growing shoots are precariously located. These shoots will grow rapidly and be weakly joined to the end of the stub. As they grow larger most of the new growth will fail and break and what is left will more than likely be more dangerous than the original limb. The result will be a disfigured and extremely ugly tree that has reduced value and also has reduced your property value (remember trees can account for up to %20 of a homes property valuation). Of course this all assumes the tree survived the original procedure in the first place and has not needed to be removed.
Now if you are wondering if there is a safe way to remove dangerous weight from a tree the answer is yes. The proper procedure is called a crown reduction and involves strategically cutting limbs back to secondary/lateral branches thereby promoting growth to an already established limb and reducing shoot growth. This form of trimming does not leave a stub which enables a tree to properly heal preventing rot. This procedure should never take more than %25 of the trees crown (that goes for any tree trimming) to keep from killing the tree. When done properly a crown reduction makes a tree safer and healthier and compared to topping is the obvious choice.
Here is a more in depth look at the practice of topping compared to crown reduction: http://www.treesaregood.org/treecare/resources/WhyToppingHurts.pdf