Tuesday, March 24, 2009

Tree Management Part I - Pruning

The calendar shows that its spring, but we still have a little winter work to complete, namely winter tree pruning. Actually, we’re very near completion of this annual work and we thought it would be an appropriate time to pass along some information about this very important activity. The majority of the actual pruning work is done by a professional arborist service (Nels Johnson Tree Care) who’s well qualified and experienced climbers have been pruning our trees at Skokie for a very long time. The Grounds Staff effort with this activity involves gathering the dropped branches and then loading and hauling to an area where we then assist with chipping.

Below: Nels Johnson climbers pruning a silver maple behind #3 green.

Above: Pruning limbs and debris clean up between #14 and #17.

Before we get into the benefits of pruning, we would like to discuss some background and dendrology.

We do most of our primary pruning activities in the dormant season for a these key reasons:
  • Viewing and evaluation of structural condition and signs of damage or disease, to determine pruning needs, are much easier when trees are leafless.
  • Climbing and actual pruning process is much easier and safer when trees are leafless.
  • Vascular fluid is inactive or motionless in dormant trees so the unsightly and insect and disease attracting “sap bleeding” is eliminated.
  • Volume of chipped branches is less and quality (for re-use potential) is best without leaves.
If you have ever seen arborists or climbers in trees with ropes and chainsaws, you may not have realized that there is a real "science" to their work. Just like most of the other procedures and practices that we carry out day to day, our tree management and winter pruning procedures, are based on the most current research.

Trees are active living organisms. Every living branch of a tree serves a purpose in maintaining the overall health of the tree. Branches serve a vital role by extending foliage out to the edge of the canopy where the leaves can photosynthesize. Energy that is captured by
the leaves, and converted into food sources, is then transported through the branch to other parts of the tree. When a live limb is removed a source of energy and food production is also lost. In turn, when a branch no longer provides energy in excess of its needs, the tree will isolate the branch and allocate its energy stores to other areas of the tree. This is why internal branches decline once they become shaded. A tree only survives by increasing or maintaining a positive energy production. Removing declining or dead limbs, does very little to disrupt the overall health of a tree, but can help a tree respond and recover better.

When a limb dies or starts to decline, a tree will attempt to create a blockade zone to prevent any infection from gaining entry to living tissue. This process is termed "compartmentalization". If an infection gets through this prevention zone the tree will be susceptible to decay organisms and potentially life threatening insects and diseases.

While the impact of decay may be minimal with a tree in the middle of the forest, it can create a hazardous situation when the tree is near valuable structures, or where people (golfers) are present. The potential for decay from a wound or pruning cut is significantly higher in fast growing trees like cottonwoods, willows, boxelders and silver maples. With these trees it is imperative that a pruning cut be made "correctly" to protect the zone of compartmentalization. Otherwise, the decline of the structural integrity of the tree will be rapid. While slower growing trees like oaks and hickory are more resistant to decay, correct pruning cuts can delay and even prevent the initiation and spread of infecting fungi.

Unlike a cut or wound on the human body, trees cannot create scabs over pruning cuts or
natural wounds. New tissue will eventually be created from where the live tissue remains, and in time this new tissue will “heal” the wound. But, unlike a scab, it will not heal the damage or infection. It will just grow over the damaged tissue, creating a weak point within the tree structure. The key to successful branch removal is to know where the zone of protection occurs and to keep it intact. This zone is termed the branch collar and contains active cells that will quickly grow over pruning cuts.

Years ago it was thought essential to apply pruning paint on, pruning cuts to deter insect and fungal activity, but research has shown little if any value in this regard. It can be useful if large branches need to be removed to improve visual appearance.

All of these concerns are taken into consideration by our pruning service. They are well trained, continue to obtain the latest in arboriculture research and they are like skilled surgeons, knowing how and where to amputate limbs with the least impact on the health of the tree and its integrity.

The benefits of our annual pruning program are considerable:
  • Removes potentially hazardous dead, damaged, diseased, or split branches. *We do leave a few dead branches as well as a few dead trees (in out of play areas), for bird nesting and other wildlife. (Another blog topic in itself coming soon– The Life of a Dead Tree!)
  • Corrects structural defects such as crossed or rubbing branches, and weak, tight-angled crotches.
  • Improves health and vigor by promoting new more disease and insect resistant growth.
  • Selective thinning opens center of trees to improve air circulation and light penetration for not only the tree but for the turf areas below. Improves aesthetic quality of tree.
  • Lower growing limbs are pruned to prevent damage to mowing equipment, improve turf quality, open vistas, and allow for reasonable shot making.
  • General shaping improves aesthetics and contains growth where necessary to prevent shot blocking issues.
A properly pruned tree - American Elm #5

Nearly all trees benefit from light pruning and with our frequent windy storms it becomes necessary for us to get around the entire course regularly. It is expensive however and so we have the course divided into sections. It is about a 7-8 year process to complete the whole course at which time we start again.

1 comment:

  1. Shaping and pruning your tree is all part of being a good care taker for it, to make sure its reserved speech for society reaches the light of day, that its existence is known as all things right.

    Ahem. Getting back to the tree. If you leave your tree unpruned, then you are going to soon find some of its branches willow away very gradually.

    -Samudaworth Tree Service


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