There are many different reasons to prune your trees, especially in the big city environment. Please be aware that “hurricane pruning” and “topping” are bad for your trees. I believe it’s important that the person or crew performing the work should have a basic understanding of tree physiology to know how those cuts will affect the overall function and health of the tree for the long term.
While it’s important to prune your trees to improve light, air movement, aesthetics and to reduce the risk of failure, there’s nothing gained from lion’s tailing or “hurricane pruning.” In fact, it will predispose your tree to insect attacks and fungal infections costing you extra money for treatments or tree removal.
Photosynthesis is the process in which a tree uses energy from the sun and carbon dioxide from the air to produce it’s own food for growth and maintenance. These sugars are formed in the leaves of the tree and then moved to other areas for growth, repair and storage. Therefore, removing too many leaves can actually starve a tree making it incapable of defending itself against insects and disease. As a rule of thumb, don’t remove more than 15% of live crown per pruning. This is also a good reason not to extend your pruning cycle beyond 2 years where larger amounts may need to be removed, which in turn, causes more stress to the tree.
Removing tree branches can reduce a heavy load but must be done with care. If too many branches are removed or stripped out, the limb reacts differently in the wind which could result in failure. Branches allow the tree to absorb energy from the wind by moving in many directions. They are surrounded by a stronger, parent limb tissue which creates taper and strengthens both the branch and the limb as a whole. Lion’s tailed branches and limbs have unnatural movement and act more like a lever arm which leads to failure. Over pruning also makes it more difficult for the tree to translocate carbohydrates and starches that are necessary to close or compartmentalize wounds. Keeping good limb and branch structure throughout the canopy is very important to overall health.
Drastic pruning is usually without good reason and won’t help in the event of tornado or hurricane force winds in the first place. Hire a certified arborist to inspect your trees so you can make an informed decision on how to reduce the risks while keeping your trees naturally beautiful. It’ll save you money and your trees will love you for it!