Reasons for Trimming
Because each cut has the potential to change the growth of the tree, no branch should be removed without a reason. Common reasons for pruning are to remove dead branches, to remove full or rubbing limbs, and to eliminate hazards. Trees may also be trimmed 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.

Before	After

Routine thinning does not necessarily improve the health of a tree. Trees produce a dense crown of leaves to construct the sugar used as energy for growth and development. Removal of foliage through trimming can reduce growth and stored energy reserves. Heavy trimming can be a major health stress for the tree.

If people and trees are to coexist in an urban or suburban environment, then we sometimes have to trim the trees. City environments do not imitate forest conditions. We want trees to complement other landscape plantings and lawns. Proper trimming, with an understanding of tree biology, can maintain good tree health and structure while enhancing the beauty and values of our landscapes.

Trimming Young Trees
Proper Trimming is essential in developing a tree with a strong structure and desirable form. Trees that receive the appropriate trimming measures while they are young will require little corrective trimming when they mature.

• Each cut has the potential to change the growth of the tree. Always have a purpose in mind before making a cut.
  
• Proper technique is essential. Poor pruning can cause damage that lasts for the life of the tree. Learn where and how to make the cuts before picking up the pruning shears.
  
• Trees do not heal the way people do. When a tree is wounded, it must grow over and compartmentalize the wound. As a result, the wound is contained within the tree forever.
  
• Small cuts do less damage to the tree than large cuts. For that reason, proper pruning (training) of young trees is critical. Waiting to prune a tree until it is mature can create the need for large cuts that the tree cannot easily close.
  

Tree Hazard Checklist

Consider these questions:

• Are there large dead branches in the tree?
  
• Are there detached branches hanging in the tree?
  
• Does the tree have cavities or rotten wood along the trunk or in major branches?
  
• Are mushrooms present at the base of the tree?
  
• Are there cracks or splits in the trunk or where branches are attached?
  
• Have any branches fallen from the tree?
  
• Have adjacent trees fallen over or died?
  
• Has the trunk developed a strong lean?
  
• Do many of the major branches arise from one point on the trunk?
  
• Have the roots been broken off, injured, or damaged by lowering the soil level, installing pavement, repairing sidewalks, or digging trenches?
  
• Has the site recently been changed by construction, raising the soil level, or installing lawns?
  
• Have the leaves prematurely developed an unusual color or size?
  
• Have trees in adjacent wooded areas been removed?
  
• Has the tree been topped or otherwise heavily pruned?