Details about Pruning
ree pruning, tree cutting, tree surgery, tree trimming –whatever terminology is used, it all involves removing branches from the crown of a tree. Tree pruning is a necessary part of tree maintenance, however live branches should not be removed carelessly.
Tree branches perform several important functions for the tree. Chief among these is the production of energy through the leaves on a branch. Since photosynthesis produces the carbohydrates and sugars that ‘feed’ the tree, removing live branches (leaves) without good cause may adversely affect the health of the tree.
Many people don’t think about pruning trees until they pose some sort of a problem such as encroaching on the house or hanging low over the street. Developmental pruning of young trees is the most cost effective measure you can do for your trees. Many tree problems and hazards can be corrected or avoided with early and proper pruning.
Tree branches perform several important functions for the tree. Chief among these is the production of energy through the leaves on a branch. Since photosynthesis produces the carbohydrates and sugars that ‘feed’ the tree, removing live branches (leaves) without good cause may adversely affect the health of the tree.
Many people don’t think about pruning trees until they pose some sort of a problem such as encroaching on the house or hanging low over the street. Developmental pruning of young trees is the most cost effective measure you can do for your trees. Many tree problems and hazards can be corrected or avoided with early and proper pruning.
There are reasonable objectives that an arborist has in mind when pruning trees that may include the following:
When pruning for future development you want to ensure there is a single dominate leader, proper branch structure and spacing. Look for future conflicts as the tree matures. You should continue pruning young trees as they grow to ensure a sturdy branch structure. The idea is to develop the weight distribution evenly over the center of the main trunk.
- Removing deadwood; removing crossing, rubbing, broken, diseased or dying branches
- Cutting branches back from buildings, sidewalks, roads and other impediments
- Opening up vistas; and elevating or removing lower branches to allow room for walking under the tree
When pruning for future development you want to ensure there is a single dominate leader, proper branch structure and spacing. Look for future conflicts as the tree matures. You should continue pruning young trees as they grow to ensure a sturdy branch structure. The idea is to develop the weight distribution evenly over the center of the main trunk.
You want to avoid large, heavy, horizontal branches, with unsound crotches, especially those with a "V" shape, as these often split. The tree in the picture at left split under the weight of a heavy snow. The appearance and health of the tree are severely damaged with a split like this. The wound opens the tree to infection which will ultimately kill the tree. Proper pruning can prevent this type of damage. Trees with strong, "U" shaped unions, like the tree on the right, are much stronger. Read this article for more details about crotch strength and branch unions. The tree on the left would have survived this snowstorm had the branch been pruned at an early age. Young vigorous trees can tolerate pruning much better than older mature trees, and therefor proper pruning is critical for sustained tree health and beauty.
Most trees have not been properly pruned throughout their lives. There are many examples of mature trees with severe defects which could have been corrected early on in the trees life. When issues have gone unchecked, large trees may require proper pruning as well. As with mature trees, weak and crossing branches should be cut off. Sizable, thick canopies might need to be thinned. Some trees may require their weak branches to be cabled to enhance their structure and safety. If you have a mature tree with structural defects the only option may be the cabling and bracing or removal of the tree.
The quality of the pruning cuts is imperative for the health of the tree. Once the decision has been made to remove a branch, the technique used by the arborist will be determined by factors that may include size, location in relation to its proximity to targets, and other considerations. All cuts should be just past the branch bark ridge and done in a manner so there are no rips or tears in the bark. The final result must leave the cambium layer intact so the wound can close over, as the cambium layer is critical in tree healing.
Once the decision has been made to remove a branch, the technique used by the arborist will be determined by factors that may include size, location in relation to its proximity to targets, and other considerations. Whatever the technique, the final result must leave the cambium layer intact so the wound can close over.
The quality of the pruning cuts is imperative for the health of the tree. Once the decision has been made to remove a branch, the technique used by the arborist will be determined by factors that may include size, location in relation to its proximity to targets, and other considerations. All cuts should be just past the branch bark ridge and done in a manner so there are no rips or tears in the bark. The final result must leave the cambium layer intact so the wound can close over, as the cambium layer is critical in tree healing.
Once the decision has been made to remove a branch, the technique used by the arborist will be determined by factors that may include size, location in relation to its proximity to targets, and other considerations. Whatever the technique, the final result must leave the cambium layer intact so the wound can close over.
Tree wounds do not ‘heal’ the way humans do. The affected tissue is chemically isolated from the rest of the tree and the cambium layer grows on the outside to close it over. You’ve probably noticed doughnut shaped rings slowly growing over open pruning wounds.
To make sure the cambium layer can grow over the pruning wound, the pruning cuts must be made carefully to avoid either cutting off the cambium layer with a flush cut, or conversely, leaving too much wood. |
Either case can cause decay to enter through the wound into the interior of the tree. Larger branches often involve several cuts to avoid the weight of the branch from ‘ripping’ down the trunk, leaving an ugly open wound or tear in the bark that may not close over. The resulting damage is very similar to the damage seen when a tree splits along a "V". Proper tree pruning technique is vital for the overall health and structure of the tree. Improper tree pruning can result in tree wounds that may permanently disfigure and structurally harm the tree, as well as give an opening for decay, disease and pest problems
The foliage must also be considered. Never remove more than 25% of the trees foliage during any growth season. In mature trees 25% can be too much. At least one half of the foliage should be on the branches arising from the lower two-thirds of the tree. Branches along the trunk help increase taper (girth of the main stem). If there are branches that should be removed but the result would be too much foliage loss, developmental pruning can be a 2-3 stage process depending on the species and location of the tree. You can leave temporary branches for several years and remove them as necessary for elevation or clearance.
The foliage must also be considered. Never remove more than 25% of the trees foliage during any growth season. In mature trees 25% can be too much. At least one half of the foliage should be on the branches arising from the lower two-thirds of the tree. Branches along the trunk help increase taper (girth of the main stem). If there are branches that should be removed but the result would be too much foliage loss, developmental pruning can be a 2-3 stage process depending on the species and location of the tree. You can leave temporary branches for several years and remove them as necessary for elevation or clearance.
"Topping" a tree, or removing the entire top of a tree, should only be done as an absolute last resort,. This method is not recommended by the ISA of the Tree Care Industry Association.
Topping often removes 50 to 100 percent of the leaf-bearing crown of a tree. Because leaves are the food factories of a tree, removing them can temporarily starve a tree. The severity of the pruning triggers a sort of survival mechanism. The tree activates latent buds, forcing the rapid growth of multiple shoots below each cut. The survival mechanism that causes a tree to produce multiple shoots below each topping cut comes at great expense to the tree. These shoots develop from buds near the surface of the old branches. Unlike normal branches that develop in a socket of overlapping wood tissues, these new shoots are anchored only in the outermost layers of the parent branches. |
The new shoots grow quickly, as much as 20 feet in one year, in some species. Unfortunately, the shoots are prone to breaking, especially during windy conditions. The irony is that while the goal was to reduce the tree’s height to make it safer, it has been made more hazardous than before.