Pruning a tree is done for a variety of reasons, and determining the intent is important in determining exactly how and when to prune. Shaping, promoting growth, reducing the size and removing damage are primary reasons for pruning. Each has a specific process, but all require an understanding of how to safely remove branches without harming the tree. Damaged branches should be removed as soon as possible, but other pruning is typically best done at the end of winter or beginning of spring.
How to Cut Branches When Pruning
For all types of pruning, removing branches and limbs should always be done where the branch meets the trunk or another branch, angled away from the branch collar. The branch collar is often seen where at the underside of where the limbs connect or meet the trunk. For small limbs, a single cut with a buck saw or pruner angled away from the branch collar is best. For larger limbs, a small notch is made a few centimeters from the branch collar on the bottom of the branch. After that cut, a complete cut further away from the trunk should be made to move the majority of the limb. Finally, a cut angled away from the branch collar is made. The intent is always to make a clean cut without leaving a stub. Ragged cuts and stubs can prevent the area from completely healing. A proper cut will result in the tree growing a callus to seal off the cut area, protecting the tree.
Pruning a Tree for Shape
When shaping a tree it is best to work with the tree's natural shape. Attempts to shape a tree outside of its natural form requires frequent pruning. Most trees are either , such as firs, or spherical, such as shade trees. Without pruning, the shape is less structured, so prune to return the tree to its natural shape by removing outer limbs. Well-shaped trees add to the aesthetics of your yard.
Encouraging Growth by Pruning
A tree that has not been pruned can benefit from careful pruning to help stimulate growth. Spherical trees are especially helped by thinning out the crown to allow more light and air to reach the lower branches. Generally, no more than 25% of the limbs should be removed when pruning for growth. Look for branches that rub against each other or those growing at a v-shaped angle when selecting branches to cut. Branches grown at u-shaped angles are much stronger than those at a v-shaped angle.
Pruning to Reduce the Size of a Tree
It is important before planting a tree to ensure that it is located in a space where it has room to grow, but a tree which has grown to interfere with a home or utility wires does need to be pruned back. Again, cutting more than 25% of its branches at once is not recommended. Reducing the size of a tree can be cutting away branches from the top to not interfere with wires or sight lines, and tools such as a rope saw or a pole pruner and looper on an extension pole help reach higher branches safely. Other times you may wish to raise the crown height, meaning that bottom branches are removed so that people or cars can pass easily beneath the limbs. Remember that the height of the living branches should be about 2/3 of the total tree height.
Pruning Damaged Trees
Tree damage can be caused by storms, insects, or the tree itself. Rubbing branches or v-shaped angles where branches meet can lead to damage. Other items to look for and remove are water sprouts and co-dominant branches. Co-dominant branches are found at the top of the tree when 2 branches are growing equal in size. It is important to remove one so that the other can be healthier. After storms it is important to always check trees for damage and remove limbs before they fall or break. Although you still want to limit how many branches are removed at once, damaged branches should always be removed immediately to prevent further damage to the tree.
Properly pruning trees allows trees to grow strong and healthy, while adding to beauty of your home and garden. Those who live in areas with codes dictating tree or crown height should pay careful attention to those limits so that extensive pruning of more than 25% of the branches is never needed at once.