Pruning is the most common tree maintenance practice. In urban landscapes, tree pruning is needed to improve overall structure, to enhance vitality, and to maintain safety and aesthetics. To optimize health and structure through pruning, there must be an understanding of tree biology. Pruning cuts must be made with an understanding of how the tree will respond. Improper pruning is harmful and can cause damage that will remain with a tree for the remainder of its life.
Reasons for Tree Pruning
- To improve the overall structure
- To increase safety by removing hazardous limbs
- To provide clearance from buildings, wires or other structures
- To remove lower limbs (crown raising)
- To remove dead or dying limbs
- To remove diseased limbs
- To improve a view (vista pruning)
- To increase flowering / fruiting
Tree Pruning Considerations
There must be considerations made before pruning any tree. The type of pruning done to young, developing trees is much different as compared to older, mature trees. Here are a few considerations:
- Tree species
- Age of tree
- Health of tree
- Structure of tree
- Safety concerns / hazardous conditions
- Tree location / site conditions
- Purpose of pruning
Pruning in the Dormant Season
To best time to prune a tree will vary based upon tree species and pruning objectives. As a general rule, the dormant season is the best time of the year for most tree pruning. Here are some reasons why:
- Minimizes the risk of insect pest issues
- Minimized threat of spreading diseases such as oak wilt or fireblight
- Results in the least impact on the tree health because stored energy is at its highest point
- Easier to visually inspect the entire crown of the tree for structural concerns or problems with no leaves in the way
- Less impact on surrounding plants and landscape
Pruning Mature Trees
When pruning mature trees, priority must be given to make sure trees are safe and hazard-free since larger trees have a higher chance of causing damage. For larger trees, tree pruning should be kept to maintaining the existing structure. The removal of live branches on larger, mature trees should be kept to a minimum. Removing a large portion of live branches can have a negative impact to both tree health and structure. Pruning objectives for older trees should be:
- Reduce the risk of failure
- Promote human safety
- Allow for clearance and passage
- Maintain structure and health
The pruning of young developing trees is important to help develop proper structure and branching patterns. Young trees that have been pruned have a lower potential for failure and will require less maintenance in future years. A larger percentage of live limbs can be pruned on younger to compared to older trees (up to 25-30% at one pruning visit)
- Training will develop trees that are structurally sound while minimizing the negative effects of co-dominant leaders, weakly attached limbs, and redundant limbs.
- Trees having fewer failures, potential hazards, and defects will make for a structurally sound future urban forest.
- Well-spaced limbs will equate to fewer limbs to be pruned in the future.
- Well-developed tree crowns will result in trees that are more aesthetically pleasing.
Never “Top” Trees
“Topping” a tree is one of the worst things that can be done to a tree. It is not an acceptable type of pruning and should not be a part of any reputable tree care company’s maintenance services.
Here is why trees should never be topped:
- May kill the tree
- Creates tremendous stress on tree health because so much live tissue is removed
- Creates decay and weakly attached branches at the point of the topping cuts
- Creates a liability by creating a hazardous tree with a weakened crown
- Topped trees can have negative value and can be considered a future expensive
Proper Pruning Cuts
Pruning cuts must be made so the tree has the best opportunity to seal off and compartmentalize the wound. Trees DO NOT heal, they only compartmentalized. No pruning cut is better than a bad cut.