A Definitive Guide to Pruning

 
Deciduous trees are those that lose their leaves in a dormant period, they can be fast or slow growing. There are many reasons for pruning a deciduous tree, pruning in general will make them safer, increase vigor and health, and will make the tree more beautiful. The value added benefits include stimulating fruit production and increased value of timber.
 
Understandably, we're hesitant to start lopping pieces off our trees; this guide has been produced to give you a helping hand on what to do and how to do it.
 
It's important to note that pruning is an ongoing process. For example, just one heavy prune will not yield a great production of fruit; it can be done if nurtured over time with proper care and attention. We often get asked to "sort out my tree". Unfortunately it doesn't work this way and a long term approach is best adopted.
 

Tools for Pruning

Pruning Shears

Most gardeners will have a set of these close to hand when they head for the garden (sometimes called clippers). There are two types of pruning shears, bypass and anvil. Bypass shears work like scissors, a convex blade is sharp and does the cutting whilst the concave side is blunt to support the stem. Anvil shears are a single usually straight blade that cuts against the center of a soft metal surface. Bypass shears make a cleaner cut whilst anvil shears can handle thicker material.
 

Loppers

These heavy duty pruners are essentially enlarged bypass or anvil shears with longer handles for greater leverage. Alongside this, they are handy for gaining access to spots that would otherwise scrape your arms or hands. Some loppers have a ratchet mechanism which increases leverage further. If you're not a strong armed type of person, these are often the better choice.
 

Pruning Saw

These are usually folding but the more modern ones can have a fixed blade. All our tree surgeons carry one of these when climbing trees because of their versatility and extremely sharp teeth. Pruning saws usually cut on the pulling stroke to make it easier for the user.
 

When to Prune

For the majority of deciduous trees, a general rule of thumb is to prune in late winter. Fruit trees are a little different, fruit trees that flower before the  first of July are best pruned in the summer when the bloom has gone. This includes species such as ornamental cherry and plum trees. Fruit trees flowering after the first of July are generally best pruned when dormant in the winter.
 
Benefits of pruning in winter are that deciduous trees will not have leaves, this allows you to see branching patterns and make the best type of cuts. During dormant periods, trees have a long time to recover and pruning wounds have time to close and repair before regrowth in the spring.
 
Some trees such as Maples or Birches will �bleed� if pruned when sap is rising; this can increase the chances of infection slightly but is not normally a problem. Other species are more susceptible to disease when pruned at certain times of the year; it often pays to consult an expert before doing any major pruning work.
 

Pruning Method #1 - Crown Thinning

Firstly, it�s worth noting that the crown is the major bulk of the tree, the part at the top, above the trunk.
 
Crown thinning is a technique primarily used on hardwood trees, it involves the selective removal of stems and branches to increase light potential and air movement throughout the crown of a tree. The intent is to improve the structure and form whilst making it difficult for pests to establish.
 
V-shaped unions are when two branches will grow from one, thus creating a 'V' shape. These are often weak and prone to snapping off in storms or bad weather. U-shaped unions on the other hand are much stronger and can be left in situ.
 
Branches growing off stems should be no more than one half to three quarters of the diameter of the stem they are attached to.
 
No more than 30% of the crown should be removed during crown thinning. If need be, more can be taken off over successive years. Crown thinning will not dramatically reduce the size of the crown.
 

Pruning Method #2 - Crown Raising

Crown raise is the most straightforward pruning method. It simply means removing the branches from the bottom of the crown to provide clearance for pedestrians, vehicals, buildings or for line of sight.
 
When crown raising, the existing living crown should retain two thirds of the total height of the tree. For example: A 30 foot tree should have living branches on at least the upper 20 foot.
 
On younger trees, branches can be retained along the stem to encourage trunk taper and to protect the tree from vandalism and sun scald. Less aggressive leaders should be selected as temporary branches and should be approx 4-6 inches along the stem.
 

Pruning Method #3 - Crown Reduction

The most common method of pruning is a crown reduction. Unfortunately, this is also the easiest method to get wrong. This method is often adopted when a tree has become too big for its surroundings. The wrong term to describe a crown reduction is 'topping'. Topping is a harmful practice and should be avoided. You can read my article on why topping hurts a tree by clicking here.
 
Crown reduction should be used as a last resort; this is because the pruning technique often results in large pruning wounds to stems, which may result in decay. Often a better long term solution is to remove the tree completely and replace it with a species that will not grow beyond the available space.
 

Wound Dressing

Research indicates that wound dressing, in particular, tar or paint, do not prevent decay and may even interfere with wound closure.
 
Wound dressing can have the following effects:
  • Prevent drying out and encourage fungal growth

  • Interfere with formation of wound wood

  • Inhibit compartmentalisation

  • Possibly serve as a food source for pathogens

For these reasons it's best to leave a pruning wound to heal naturally and let the tree deal with it in a way that�s suitable.

 

Summary

Pruning is a vital ongoing process of a trees lifespan. Every year trees fall over or become out of control when it is often preventable by applying proper pruning techniques.
 
Take a look at the crown lifting, thinning & reducing page for a little more information on these techniques/ methods.
 
If any advice is needed on pruning, don't hesitate to get in touch. If you will be conducting the prune yourself, it may help to read my article on pruning cuts to help you determine exactly how to cut the tree.
 
Thanks for reading.
 
Sam Clark
Tree Surgeon
SPC Tree Services
 

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