The pruning elevating and dead wooding of trees, are three of the most common arboricultural practices, and ideally should begin while the tree is young. This is when many of the problems associated with healthy structural development should be addressed; before they get out of hand.
(this tree has an ideal structure with a strong central leader and well spaced scaffold limbs. By maintaining a good structure, many future problems can be avoided.)
(this tree has a poor structure with multiple competeing leaders and an over abundance of crowding scaffold limbs unless corrective pruning is done this tree will likely experience future problems.)
It is important to remember that there is a difference between pruning and trimming. Pruning is training method used to encourage trees to grow in a desired direction or shape, or to encourage the growth of a particular structure. Pruning is directed purposeful cutting toward a predetermined end. The goal in the Pruning and thinning of young trees, is to establish a single strong trunk with sturdy well spaced scaffold limbs. A general rule of thumb for the vertical spacing of permanent limbs, is to maintain a distance equal to approximately 3% of the tree’s eventual height at full maturity.
Pruning at this early developmental stage in a trees life is to eliminate such problems as co-dominant stems and narrow weak V-shaped branch unions with bark inclusion, which can be prone to splitting if allowed to develop. Typically stronger branch unions are more open and somewhat U-shaped.
Provided it is correctly done, pruning also promotes strong new growth and helps to produce a well shaped healthy crown. It also serves to maintain ventilation which reduces potential fungal problems and allows light into the canopy. When pruning, thinning and shaping it is essential to have a good understanding of how trees develop. Severe over pruning and thinning should be avoided as these practices produce misshapen trees and promote the growth of tip heavy limbs that are prone to failure. This practice of over pruning and over thinning is known as lion tailing.
(This pruning style is known as lion tailing and is very bad for trees, because it severely reduces the trees ability to manufacture food from sunlight. Also a tree pruned this way is more likely to suffer damage from storms. Repeated defoliation of this kind can predispose a tree to stress and eventually decline. We strongly advise against it.)
Regular repeated butchering can lessen a trees photosynthetic ability by reducing its capacity to manufacture the sugar needed for energy to sustain healthy growth and development. Once valuable stored energy reserves are depleted the tree becomes stressed and is inevitably weakened and begins to decline. Topping also known as decapitation or dehorning, is another barbarous practice that is very destructive to larger shade trees (hardwoods in particular). Unlike normal branch growth that develops in a socket of overlapping wood fiber or tissue, the radical new growth that is forced about by topping is poorly anchored usually only in the outer most layers of wood fiber growing from the parent trunk or limb. Crown rot is another problem frequently associated with topping which proliferates weak branch or crotch unions and opens the crown to fungal infections and disease pathogens.
(Hurricane Tree Specialists does not engage in the practice of topping trees and we advise anyone considering it to think twice. Contrary to popular opinion, topping dose not make a tree safer and infact will most definately make it more likely to fail in the future.)
Contrary to popular belief, topping does not make a tree safer and unless restoration attempts are successful the probability of structural failure is compounded exponentially over time.
(The new growth that has sprouted from this topping cut is approximately 4 years old you can plainly see that it is attached only to the outer sapwood that formed after the cut was made, as the center of the old branch is completely rotted It will likely fail in the future.)
(This tree was topped approximately 15 years ago it subsequently failed in a wind storm because of rot in the crown. The carport was damaged and had to be reconstructed.)
Hurricane Tree Specialists does not engage in the practice of topping trees and we advise anyone considering it of the damaging effects of this destructive practice. It is a good idea to steer clear of individuals or companies that advertise topping as a provided service, as this is one of the hallmark characteristics of an amateur who is unfamiliar with correct pruning methods, or is otherwise unconcerned with the damaging effects of this counter productive method. Finally trees should be an asset that enhances the value of a property and not a potentially hazardous liability.
Careful pruning and thinning can strengthen a tree by removing weak or diseased limbs and enabling it to channel it’s energies into stronger growth. Trimming on the other hand, is simply removing the excess growth and reshaping and already existing structure. Once the permanent limb structure of a tree has been established all subsequent cutting is basically to maintain that structure by trimming away any limb work that has become over grown or out of balance, and by removing any epicormic growth (suckers).
The amount of growth removed during pruning operations, depends largely on the trees needs. Generally speaking younger trees tolerate heavier pruning better than older mature trees. A good rule of thumb is no more than 15% to 20% or one fifth should be removed, anymore than this constitutes over pruning which as discussed earlier can damage the tree and lead to problems. Some trees never recover from repeated over pruning and cutting.
( This old oak tree was repeatedly topped and over-pruned over a period of years and finally died. )
When to prune, is another common question that sometimes leads to confusion. The cutting away of deadwood or diseased limb work can generally be done at any time during the year. Some good rules to remember, are cuts made just before spring heal the fastest, while cuts made in late summer usually do not begin to heal until the following spring, and so growth is maximized and wound closure is fastest if pruning takes place in late winter before the spring growth flush.
( Examples of different pruning wounds in various stages of closure )
Heavy pruning just after the spring growth flush should be avoided, as trees have expended a great deal of stored energy to produce foliage. Too much foliage loss at this critical time can severely stress a tree. Some tree diseases such as oak wilt (Ceratocystis fagacearum), which is systemic in its function can be spread when pruning wounds allow fungal spores access into the tree. Susceptible trees should not be pruned during active transmission periods, which for this disease is generally from April to June.
( spore filled fungal mats of oak wilt disease (Ceratocystis fagacearum) growing under bark )
Trees such as the three examples below, birches (betula), walnut (juglans) and maples (acer) should be pruned while in full leaf to avoid the excessive bleeding that can take place in early spring when the sap flow is high.
Winter temperatures in northern climates can also put certain constraints on when to prune. Here in Florida however this is less of a concern. The proper course of action to be taken when setting out to prune should be firmly established before any work begins. For instance is pruning needed to improve vigor or aesthetics? Perhaps it is to elevate low hanging limbs that are interfering with housetops, sheds, satellite dishes and the like. It could be that more air movement and light is desired in which case some thinning may be in order.
Another factor, could be pruning to provide open passage for electrical transmission lines. If this is the case it is advisable to hire a reputable private company instead of waiting for the power company to send someone. Often times these people needlessly butcher trees by using methods such as drop crotching, which is the pruning back of large central limbs to outward pointing laterals. While this method is effective it often times leaves the tree horribly disfigured.
Anyone who has driven on today’s streets and avenues has undoubtedly seen the damaging effects of this destructive method (trees with the entire central portions removed). Directional pruning is the preferable way of accomplishing the task of accommodating power lines. This method opens only enough space for safe wire passage, while preserving as much as possible symmetry and balance (aesthetics). Drop crotching should only be done as a last resort.
(This tree growing near power lines has been pruned using the directional method, ultimately its form will not be as disfigured as the trees pictured above. Obviously large growing trees like this one should never be planted under power lines. Most problematic trees in the urban environment are that way because the planting site is not suitable for their ultimate size at maturity. Indeed better comunication between city planners, landscape designers and arborists is needed.)
(Anatomy of a branch image courtesy of Shigo and Trees Associates)
No discussion on tree pruning would be complete without covering proper pruning techniques. While there are many different pruning methods, the correct procedure for removing a limb is basically the same for any tree. First an undercut should be made approximately 18 to 24 inches (45.72 to 60.96 cm) from the branch collar. Think of this as an intermediate area between the branch and the parent trunk or limb. This is usually identified by a raised sometimes rougher and slightly darker ridgeline of bark. The branch collars on some trees will be more pronounced than on others, depending on species.
Next make topcut just beyond the first cut.
First make an undercut out beyond branch collar.
The final cut should be made just outside of the branch collar care should be taken to prevent the bark from tearing.
( Properly pruned and elevated trees no butchery )
Next a top cut should be made approximately one ¼ inch (.635cm ) out beyond the undercut (this is about the thickness of a chainsaw bar). Once the limb falls away the remaining stub can be removed. Care should be taken here to avoid cutting into the branch collar, as this can create wounds in the parent trunk or limb, which can give disease pathogens unobstructed acsess into the tree. This 3 step procedure for limb removal is the best way to prevent tearing of the bark and peeling that would otherwise occur. Sometimes more than 3 cuts are necessary to meet this standard, depending on the weight and size of the limb being removed not to mention any obstacles that may be in the way.
How often to prune, is another common question. The average pruning cycle for most shade trees is approximately once every 3 years. With a little knowledge and understanding it is well within the capability of most able bodied home owners and do it yourselfers to prune their smaller trees and shrubs, the pruning and elevating of larger trees however should be left to professionals. This work is often times dangerous and can pose substantial hazards to personnel and surrounding property.
If you have trees and are interested in having some pruning done, give us a call we can advise you on which pruning methods would be most beneficial for your specific application. We can also help to organize a schedule for follow up inspection and maintenance. Whether it’s the removal of a couple of limbs, or a large scale pruning operation on multiple trees, my team and I have the proper equipment and training to ensure a safe quality job every time.
(poorly structured branch union (co-dominant trunks) with definite bark inclusion)
(good strong branch union no bark inclusion)
We give a personalized, hands on quote of your Pruning needs!
Steven Braden, Certified Arborist