Pruning trees can be one of the most difficult and technical tasks you take on. You prune too much, you risk the tree's health. Too little and you haven't done your job.

So why prune when trees in the forest do quite well without it? Although forest trees grow quite well without somebody coming along and trimming them, landscape trees require a higher level of care to maintain their safety and aesthetics. For this reason, pruning must be done with an understanding of how the tree responds to each cut. Improper pruning can cause damage that will last for the life of the tree, or worse, shorten the tree's life. Each cut has the potential to change the growth of the tree and this is why no branch should be removed without a reason.

Although seemingly risky, pruning helps your tree by removing dead branches, prevents crowding or rubbing limbs, and helps eliminate hazards. Trees may also be pruned to increase light and air penetration to the inside of the tree's crown or to the landscape below. In most cases, mature trees are pruned as a corrective or preventive measure.

There is a difference between pruning and routine thinning. Routine thinning does not necessarily improve the health of a tree. Trees produce a dense crown of leaves to manufacture the sugar used as energy for growth and development. Removal of foliage through pruning can reduce growth and stored energy reserves. Heavy pruning can be a significant health stress for the tree.

Because people and trees have to coexist in urban or suburban settings, we sometimes have to modify the trees for the sake of all. City environments do not mimic natural forest conditions and therefore safety is a major concern. Also, we want trees to complement other landscape plantings and lawns. Proper pruning, with an understanding of tree biology, can maintain good tree health and structure while enhancing the aesthetic and economic values of our landscapes.

So when should one prune is often a common question. As a rule, growth is maximized and wound closure is fastest if pruning takes place before the spring growth flush. Some trees, such as maples and birches, tend to "bleed" if pruned early in the spring. It may be unsightly, but it is of little consequence to the tree. Otherwise, most routine pruning to remove weak, diseased, or dead limbs can be accomplished at any time during the year with little effect on the tree.

Oak wilt can be spread when pruning and wounds allow spores access into the tree. Susceptible trees such as these should not be pruned during active transmission periods.

Heavy pruning just after the spring growth flush should be avoided. At that time, trees have just expended a great deal of energy to produce foliage and early shoot growth. Removal of a large percentage of foliage at that time can stress the tree.

What are pruning terms and techniques? Cleaning is the removal of dead, dying, diseased, crowded, weakly attached, and low-vigor branches from the crown of a tree.

Thinning is the selective removal of branches to increase light penetration and air movement through the crown. Thinning opens the foliage of a tree, reduces weight on heavy limbs, and helps retain the tree's natural shape.

Raising, removes the lower branches from a tree in order to provide clearance for buildings, vehicles, pedestrians, and vistas.

Reduction reduces the size of a tree, often for clearance of utility lines. Reducing the height or spread of a tree is best accomplished by pruning back the leaders and branch terminals to lateral branches that are large enough to assume the terminal roles (at least one-third the diameter of the cut stem). Compared to topping, reduction helps maintain the form and structural integrity

A common mistake is to remove too much inner foliage and small branches. It is important to maintain an even distribution of foliage along large limbs and in the lower portion of the crown. Over thinning reduces the tree's sugar production capacity and can create tip-heavy limbs that are prone to failure.

If you are uncomfortable in taking on the task of pruning your own trees, there are professional arborists that know just how much to prune and not to prune as well as a knowledge of proper tree and branch removal.