Structural pruning is a must if you want your young shade trees to grow to be balanced with a healthy framework of main branches. This type of pruning is generally reserved for deciduous trees and it is best done when the trees are young, usually beginning in the year of or the year following planting. Plan to complete structural pruning in late winter, when the trees are still dormant. The only exception is those that are high sap producers in spring, like birch and maples. These are usually structurally pruned in summer. The following tips can help you complete this task successfully.
Tip #1: Size Matters
Structural pruning, also called training, is reserved for young trees. This means all branches that are pruned are relatively narrow in width. Use your fingers as a guide. If the branches you are pruning are no wider than the width of two of your fingers, then the tree is still in the structural pruning stage. If the branches are wider, then you are pruning a more mature tree and the chances of causing injury or leaving the tree open for decay increases with the removal of each of these larger branches.
Tip #2: Determine a Branching Style
Before making the first cut, you need to decide what you want the mature tree to look like. If you prefer narrower trees, you will want one main trunk going to the top of the tree, with all lateral branches coming off this trunk. This means trimming off all but one of the vertical upright branches, and choosing the vertical branch most in-line with the trunk below the lowest scaffold of lateral branches.
For a wider tree, three "trunks" are preferred, with each supporting their own framework of lateral branches. Opt for one central trunk and two vertical uprights. The first vertical you choose should emerge slightly lower than the lowest tier of lateral branches. The second upright will be on the opposite side of the first but offset so it emerges from the trunk slightly higher. Trim off all additional vertical branches.
Tip #3: Maintain the Trunk
There will be branches that try to grow in below the main scaffold of canopy branches. This not only creates a twiggy growth on the trunk, it can also weaken the tree if these branches are allowed to reach maturity. Trim these off with bypass pruning shears, cutting them off flush to the trunk. By doing this annually, the branches will be small enough to remove without difficulty. Also, inspect the base of the tree and cut off any twiggy growth trying to come up from the roots.
Tip #4: Create a Perfect Canopy
Finally, keep your canopy branches maintained. Start by removing any dead or damaged branches back to the healthy wood. Next, examine the main lateral branches as they come off the trunk or vertical leaders. Each main branch should emerge at a slight angle. You don't want to keep branches that are perfectly horizontal or those that angle upward sharply. Next, remove any small branches growing off the laterals if they are crossing and rubbing on another branch, of if they are growing perfectly vertical.
Pruning done in the formative years will minimize the need for extensive pruning once the tree is mature. Contact a local tree trimming service if you need more help with maintaining your young shade trees.