Winter Pruning

Trees need good structure. Good structure will neutralize the harmful effects posed by wind, rain and gravity. And the basis for good structure in trees is to prevent structural defects from cropping up on the trunk and lateral branches. The worst of these are co-dominate stems, over-sized branches and cluster branches.

They are commonly found associated with young, fast-growing saplings. The goal is to nip them in the bud before they get bigger and more costly to eliminate later. Structural pruning should start the year following plant installation and be repeated every 4 years over the next 25 years. Use the following illustrations and definitions to help locate and manage by pruning any major structural defects on your young trees.

• 1 Co-dominant stems: Two or more equal-sized stems competing for the leadership role at the top of the tree is a no-no. Like an orchestra guided by a sole conductor, only one stem is needed. Maintain a single central stem/leader by lopping off the weaker of the two. Maybe, if necessary, even remove one or two shoots located directly below the new leader to more strongly assert the latter’s dominance at the top of the tree.
• 2 Over-sized branches: Stems fitting this description are easy to find. They are much larger in diameter than their brethren. Here’s a rule of thumb to help you to identify them. For sound structure, no stem should be larger than 50% of the diameter of the stem at the point of attachment. For example, if a 2 diameter-inch stem is connected to a 6 diameter inch- trunk, all is well. However, if a 4 diameter-inch stem is connected to the same 6 diameter- inch trunk, that’s a no-no. It’s growing too fast at the expense of the rest of the branches. You have two choices for correcting this problem. The first is to remove the obese branch entirely. The second option is to remove a portion of the offending limb, usually about a third of it. This will slow its growth by denying it the extra carbohydrate (energy source) found in the lopped off portion of the branch. Eventually the shortened branch will come into compliance with the stem diameter ratio mentioned earlier. TIP: The second option is usually selected when total stem removal will leave a huge gap along the trunk of the tree.
• 3 Cluster branching: Two objects cannot occupy the same space at the same time. This law of physics also applies to trees. Unfortunately, this condition is a common problem on young trees, especially those with opposite branching patterns (maple, dogwood, catalpa, etc.,). Here’s a tip leading toward a solution. Alternate branching is far superior structurally to opposite branching. Strive to get young trees into this zig-zag branching arrangement through the routine removal of offending branches. Remember, as they increase in diameter, branches located opposite each other will eventually place a lot of stress at that point along the trunk. The stress can often lead to breaks. This is a big problem with the Callery Pear (Pyrus calleryana). It inherently produces this type of structural defect and shouldn’t be planted without a future commitment to training.