With appropriate choices, trees should not need to be pruned very often. Unfortunately, many American gardens have less than perfect choices for trees. Sometimes this is an inherited problem, sometimes a weakness on the homeowner’s part and sometimes lack of knowledge. Whatever the cause, pruning these trees may be inevitable.
As with pruning shrubs start by taking out dead branches. Then look for branches that are crossing over other branches. If these crossed branches are not removed there is a danger that the two branches will grow together, frequently allowing moisture to gather followed by decay where the two meet. Too many branches in the center will also inhibit light and air to the middle of the tree.
Next, look for branches that are growing at a very sharp angle to the main trunk. As these branches mature, the small angles are more likely to snap in a wind. So remove them while they are still small.
Finally, look for the general shape of the tree. Trimming ‘sports’ and small shoots around the base of the tree will enhance that natural shape.
All the above is minor tree work, but should be done with care. Even small branches can be heavy, so use caution when dealing with them. Never stand under the branch that you are removing; use eye protection and if necessary head protection. Take small pieces off a large branch, rather than taking down the whole piece at one time. Do not trim branches that are near power lines.
Major tree work is best left to professionals.
Topping trees should never be done. Frequently you will see mature trees ‘reduced’ in height by lopping off all the major branches. New growth is thin and short in comparison to the trunk, and takes on the unaesthetic look of a child’s stick drawing of trees. The once majesty of the tree is gone. More importantly is that the tree itself will suffer. The new growth that is put out is weak and far more likely to fall than the older sturdy branch. The wounds on the tree are large and liable to decay and thus become a conduit for disease to the inner part of the tree. So if someone offers to do this treatment to your tree, politely move onto another person.