Pruning can be preformed any time of the year, but that being said spring & early summer is best due to trees ability to heal wounds. Removal of dead, dying, diseased, or broken branches can done any time with little negative effect.
Spike or tree gaffs should never be used to climb a living tree that is being pruned. Spikes go on the climber's leg and foot and have a metal spike that is used to stab the tree to climb up. This practice harms the tree by introducing holes through the protective bark or the tree into the live wood. Each hole allows for decay fungus, insects and disease to enter the live wood of the tree without having to bark barrier to help protect it. Using gaff's or tree spikes is a bad practice.
A proper pruning cut is important to allow the tree to properly heal the wound created by cutting the branches. The cut must be made in front of the branch collar, not flush to the trunk. This is important being the branch collar contain the tree wound closure mechanism allows the tree to compartmentalize to create a protection zone to stop or slow the rate of decay. If the tree can't create this protection zone then each spot where a branch was removed will rot beyond the wood of the branch and into the trunk of the tree.
Pruning can provide many benefits to a tree by improving health overall by removing deadwood, poor branch connections; that reduces the risk of whole tree, branch or stem failure. Pruning can also hurt a tree if done improperly by untrained workers can harm or even kill the tree. There is still one common practice being used even with 25 years of literature and seminars; "topping" is still occurring that kills trees. Also not pruning a tree can harmfully for the health of the tree.
Then looking at a tree to be pruned there should be a clear pruning objective determined by two factors; first-factor is what the client wants to achieve by pruning and second-factor is can the first-factor be achieved without harming the health of the tree, besides the pruning of a tree is for the benefits that it provides a tree!
Now many factors to determine if what the client wants to achieve is right for that tree. The pruning objectives need to take into consideration: the size of the tree, location, growth rates, structure, species, overall health, client expectations, site usage, and pruning cycle.
Improper or bad pruning can kill trees!
There is still one common practice still being used even with 25 years of literature and seminars; "topping" is still occurring that kills trees.
The best examples of trees with great structure are in the forest where trees grow with high competition for survival. These trees grow tall fast to reach the sunlight that they need to make food. So, in the forest that is established the trees have a proper trunk diameter(dia) to branch dia ratio; simply meaning that the branches are not equal to or larger than the trunk of the tree and the tree has one central leader. This ratio is important for a tree so the branches don't try to become a dominant leader that is formed with a weak branch union/connection. This type of pruning system is called "natural" and it should be started as soon as, after planting a new tree.
The most common pruning objective performed by Treeman Tom LLC. Reason is a simple one, clients want to reduce the risk of trees damaging property or persons.
Clearing an obstacle like a building, playground, shed, utility service, line-of-sight, traffic, the health of other plants, or pool. An example of this type of pruning is when clearing branches above a roof by 12 feet in order to clear the house and create more air movement and sunlight to dry the roof to stop moss from growing.
Pruning to maintain tree health normally includes the removal of infested, infected, damaged, dead, broken, or rudding branches.