The first step to proper pruning is determining the type of tree to be pruned. This is important because knowing the species of tree you are pruning will dictate when the best time to prune the tree will be. Read my previous post for more information on when to prune. Next, determine your reason or desired outcome for pruning the tree. Are you just removing dead branches, trying to reduce the size of the crown, trying to let more light through a tree or get a better view? One of the biggest reasons for pruning is to correct the growth form of the tree or shrub. It is also important to keep in mind that you do not want to remove more than 25% of the live canopy of a mature tree. Removing too much of the tree’s leaves will reduce its photosynthetic capacity and therefore hinder the tree’s ability to make food for itself. Dead limbs can be removed all at once and at any time without compromising the tree.
After determining the desired outcome, you’ll want to make a plan as to which limbs to remove. I like to start with removing any dead limbs. Often with the conifers in the Tahoe area, just removing the dead and broken limbs is enough to dramatically impove the aesthetics of a tree. Do this on all of the trees on your property and it will look like a park. Next, I look for limbs with poor growth form or structure. Poor growth structure can be codominant leaders, especially if the union or crotch of the limbs forms a “V” instead of a “U” shape. “V” shaped unions often break as a result of included bark.
Read more about codominant leaders and included bark here: http://www.treedictionary.com/DICT2003/tree_pruning/codom_leaders/index.html
Another form of poor growth structure are limbs that originate from a limb on the outside of a tree, but grow towards the middle or trunk of the tree. These limbs often get tangled together with other limbs or rub against each other. Removing limbs that rub against each other is important, whether the limbs originate from the outside or inside of the tree. When limbs rub together, the bark usually falls off and leaves the wood open to decay or invasion from parasites.
After you have made a plan, it’s time to start cutting. Knowing how to make proper pruning cuts is essential to the health of your tree. When pruning a limb, you will always want to make you cut just outside of the branch collar. Cutting into the branch collar itself will inhibit the tree’s ability to compartmentalize or heal the pruning cut. Cutting too far outside the branch collar will leave ugly stubs on your tree. You always want to make sure your cuts are clean, so make sure your handsaw or chainsaw is sharp before you start cutting. On large or heavy limbs, you will need to make 3 cuts to remove the branch. The first one should be about 6” from the branch collar and on the bottom of the limb. Make your cut only about 1/4 to 1/3 of the way into the limb or your saw will get pinched in the kerf or cut. This will keep the bark from tearing when you make your next cut directly above it. Now you will be left with a stub which you can cut flush to the branch collar.
When removing the leader of a branch or the main leader of a tree, you will not have a branch collar to cut flush against. In this case, you will want to look for the branch bark ridge. This is where the bark is pushed into a ridge where the union of the 2 limbs comes together. Now imagine that you have a line perpendicular to the leader that you are removing that touches the branch bark ridge on one side. For your final cut, you will want to bisect the angle between the imaginary line and the branch bark ridge.
It is never recommended to remove the leader of a conifer. This is called topping and essentially leaves a conifer with poor growth form. You can read more about topping here. http://www.treesaregood.com/treecare/topping.aspx
With proper cuts, most deciduous trees can have their crown height reduced. You always want to make sure you cut back to a lateral branch when doing this. The following urls have some great information on how to prune trees.
Feel free to call Alpen Tree Experts with any pruning questions or if you would like an estimate for pruning the trees on your property.