Spring has sprung. The best time for pruning is early spring- late February and early March. If you are going to prune this spring do it quickly before the trees and shrubs leave dormancy behind and begin active growth. This is the time when wounds heal more readily and flower buds can be easily seen.
Proper pruning can maintain plant health. The following are good reasons to prune trees and shrubs:
- To eliminate branches that cross- tree limbs will grow into one another. Therefore, we should remove unwanted branches that are on course to cross one other or are already crossing.
- To eliminate dead or diseased branches.
- To control and shape growth.
This white mulberry is an example of what happens when crossing branches are not removed. The narrow crotch makes it difficult to prune with three cut method.
You should never remove more than 20% off a healthy middle aged tree- much less for young trees. Young trees should be pruned sparingly and only with the intention of training. A single leader should be determined early to avoid too much thick growth on top which can lead to breakage in storms and heavy winds.
Proper cuts:
Pruning causes a tree wound. Therefore make the cleanest, smallest possible cut. Use a three cut method to avoid further injury to plant tissue. First, a cut is made under the branch only half way through several inches out from the collar. The second cut is made just outside of that in the opposite direction. This removes the weight so that you can make a clean cut at the branch collar for the third cut.
The wound doesn’t actually heal, rather it is callused. This is also called the woundwood. This tissue forms a donut when made properly. When not made properly it is uneven due to being cut too closely to the trunk.
Wound dressings were once applied regularly but no real evidence suggests it is necessary.
Exceptions to early spring pruning.
For spring flowering shrubs, spring pruning will remove flowers so the option is sacrifice, or preferably shape immediately after bloom. For example, trim your lilacs after they finish blooming.
Only prune Oaks late fall or winter: Many trees are fine to trim any time of the year. But oaks are an exception. Never prune oaks in the spring, summer, or early fall as this makes them prone to Oak Wilt. Oak wilt is caused by the fungus Bretziella fagacearum (previously Ceratocystis fagacearum). The wounds also make them vulnerable to pests. Therefore, only prune oak trees when they are dormant.
SAFETY NOTE: Be safe, never prune a branch greater than 2 inches in diameter. Call a professional arborist for larger tree limb removal.
If you are looking for specific guides, Iowa State extension has a wide range of free PDF’s on pruning that can be found below: