Photo examples of thinning

Inappropriate thinning examples
Appropriate thinning examples
The best way to thin a tree is to structurally pruning it!
Before thinning: Canopy is full of foliage creating dense shade below. To thin the canopy to allow more light to reach below or to make the tree more stable in wind, remove branches from the edge of the canopy as shown below. This typically means making 1.5 to 3 inch diameter pruning cuts inside the canopy about half way back to the trunk. This results in a thinner canopy, especially toward the edge of the canopy which allows air to pass through it. A thinner canopy moves less than a canopy before thinning, therefore reducing damage in wind. Sometimes branches are removed back to the trunk to thin the canopy.
After thinning: Most removed foliage should come from branches and stems that compete with the leader. The lower right branch was also removed on this tree to raise the canopy.