when to hire a professional tree surgeon 

Pruning large trees is a safety issue beyond the training and experience of home gardeners. Hiring a professional tree surgeon is the best approach for most tree pruning jobs like tree trimming or tree removal. Look for arborists with certification like Bennett’s tree care check there certs if they can’t provide them then why there is no excuses you don’t just loose them it its years to get qualified and cost a lot of money to do so losing a certificates is careless would not happen.

Pruning objectives for mature trees

As trees mature, pruning should be based on pruning purposes. Do not just indiscriminately remove branches. The pruning purpose determines how to prune, which in turn determines the type of pruning cuts used.  lists common purposes, how and types of pruning cut.

Prune Mature Trees with a Purpose

purposes

  • Reduce risk of failure 

  •  Wind loading 

  • Structural pruning

  • Maintain health 

  • Develop root structure

  • Improve view Reduce shade Influence flowering and fruiting

how

  • structural

  • cleaning

  • crown lifting

  • crown cleaning

  • crown reduction 

  • crown cleaning 

pruning suited for purpose  

  • thinning  or reducing limbs in size  

  • reduction in height 

  • removing lower limbs 

  • thinning, deadwooding, remove crossing limbs

  • tip reducing

how much can be removed

Do not indiscriminately remove branches with live foliage as this can add stress to the tree. The amount of live wood and foliage that can be removed per season depends on the growth rate of the tree. As a rule-of-thumb for healthy trees, 10-15% of the live foliage may be removed per season. For actively growing medium age trees (mature phase of life cycle), without growth limitation factors (such as a dry site or restricted rooting spread), up to 20% of the foliage may be removed per season. For young actively growing trees (growth phase of life cycle) without growth limiting factors up to 25% of foliage may be removed per season. More severe pruning slows root growth by shifting the root to shoot growth ratio. This adds significant stress to the tree. Heavy pruning also reduces carbohydrate reserves, making the tree less tolerant of insects, diseases, and drought stress. Do not remove live wood and foliage from trees showing stress.

General pruning guidelines
  1. To minimize the potential for decay, make thinning cuts on branches with a branch collar when ever possible.

  2. Ideally, pruning cuts are made on branches two inches and less in diameter. These small wounds minimize the potential for internal decay. Unless there is a strong justification (taking into account the potential for a decay column) avoid removing branches larger than four inch diameter. Large wounds predispose some trees to internal decay.

  3. To maintain overall tree vigor, at least one-half of the foliage should be in the lower two-thirds of the tree. The lowest limb should be in the bottom 40% of the tree’s height.

  4. Pruning should maintain the tree’s natural shape.

  5. Avoid topping a tree. Topping opens the tree to internal decay. Regrowth of water sprouts (adventitious shoots) is structurally unsound.

Dealing with structural defects

Most storm damage is Structural problems of this should have been corrected while the tree was in the early growth stage. Little can be done to correct structural defects on mature trees without predisposing the tree to internal decay and creating an unsightly shaped tree

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crown cleaning

Cleaning is the removal of dead, diseases, detached and broken branches. Most pruning of mature trees falls into this category. Trees under stress or declining trees may need cleaning every few months to years. All dead wood may be removed at one time. In cleaning, do not remove healthy branches and live foliage. Do not clean out healthy growth in the tree’s interior.

Removing dead branches – To minimize risk if the branch were to fail, it is advisable to remove any dead branch larger than two-inch diameter and higher than 30 feet. Dead branches may also become a source of insect and disease pressure in the tree.

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crown thinning

Thinning is the selective removal of smaller branches (two inch diameter and smaller) in the leafy upper/outer canopy. Thinning cuts are primarily used. Since thinning is in the upper/outer canopy, it requires a trained arborist with a high level of skill. Thinning sometimes can be expensive but a big purpose in tree maintenance.

Benefits of thinning

• Thinning is the best way to minimize potential damage caused by snow loading, the primary factor leading to tree failures in Colorado. Thinning can reduce limb weight in order to compensate for structural defects.

 

• Thinning increases light penetration into the tree interior. This can invigorate the tree and help retain the tree’s natural shape. Thinning may reduce shade to under story plants below the tree. Shading by maturing trees often limits the vigor of lawn and flowers under the tree. However, increased light penetration into a lawn may invigorate the lawn adding stress to an old or declining tree due to root competition for water and nutrients.

• Thinning is a technique to partially open a view without removing or structurally impacting a tree.

crown lifting 

Raising is the removal of lower branches to provide clearance for people, traffic, buildings, or a view. When removing lower branches, maintain at least one-half of the foliage in the lower two-thirds of the tree. The lowest branch should be in the bottom 40% of the tree’s height Raising should be part of the tree’s structural training while young. Ideally raising would be done before branches to be removed exceed a two-inch diameter. The potential for decay is high when the branch removed is larger than four inches or when a two inch and larger branch is greater than half the diameter of the adjacent trunk (no branch collar to suppress decay). On many trees, lower branches make-up a significant portion of the tree’s entire canopy and cannot be removed without significantly impacting tree health and appearance. When the branch to be removed is larger than two inches, consider other alternatives. Can the clearance required be achieved with thinning and reduction cuts out along the branch rather than removing 

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the entire branch? Leaving some small diameter branches on the lower trunk for a year helps close pruning wounds and lessens the potential for trunk cracking. Excessive removal of lower branches increases the potential for tree failure by decreasing trunk taper, causing trunk cracks and decay and transferring weight to the top.

tree reducing  / height reduction 

Reducing is selective removal of branches to decrease the height and/or spread of a tree. It requires the use of reduction cuts to remove larger branches back to smaller branches.

Reducing is the most effective method to reduce potential wind damage on large trees with structural problems. Reducing and thinning both decrease potential failure from snow loading; however the thinning may better address issues without predisposing the tree to internal decay. Not all trees can be reduced without predisposing the tree to decline and death. Crown reducing requires the extensive use of reduction cuts which can predispose the branch/trunk to internal decay. On older trees showing stress or decline, reduction cuts can accelerate decline and death

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I’m concerned about my tree in winds, but I really don’t want to lose the shade. Do I really need to have the tree pruned or removed?

This is a two-part question.

  • First, does the tree show signs of being highly susceptible to storm damage, i.e., previous storm damage, dieback or dead branches, structural problems such as co-dominant trunks, weak branch unions or internal decay

  • Second, if yes, what would the tree or branch hit should it fail? If it would cause significant property damage or threaten life, the tree should be pruned or removed as a preventive measure.

  • Cleaning and thinning may reduce the potential storm hazards without compromising the shade. In some situations the risk of failure can not be reduced without removal. Remember that healthy structurally sound trees are generally windfast even when mature. Storm damage is usually, but not always, related to structural problems that could have been corrected with proper structural training when the tree was young

How should declining trees be pruned?

Focus on cleaning. Avoid removing live wood and foliage as this could speed the decline. Removing live wood lowers the auxin content which is the hormone that promotes root growth. Removing foliage reduces photosynthesis and levels of stored carbohydrates that the tree is living on