Tree Lopping: What is it and what can be done instead?

“Do you lop trees?”
It all depends on your definition of ‘tree lopping’.

Lopping is a very general term used for a multitude of aboricultural activities.

  • Do you prune trees?
  • Do you cut branches?
  • Do you make trees smaller?
  • Do you remove trees?

These are all queries inferred by the question “Do you lop trees?”

 

What is Lopping?

To a trained arborist, the term ‘lopping’ has a specific, more technical meaning.

It stands for a practice that professional arborists are taught not to do.

It is a practice that is detrimental to trees.

So when asked ‘Do you lop trees?’, professional arborists have to decide in what way the word ‘lopping’ is being used before they answer.

The ACT Tree Protection Act 2005 specifically prohibits lopping and lists it as a tree damaging activity.
The Act defines ‘Lopping’ as the cutting of branches or stems of a tree between the branch unions.
By comparison correct pruning normally involves the cutting of branches back to a fork or branch union.

In Principles of Tree Hazard Assessment and Management’[i], Dr David Lonsdale states:

‘Topping (usually referred to as ‘Lopping’ in Australia) is highly disfiguring for most kinds of trees…
Topping is likely to cause severe xylem dysfunction and decay in major structural parts of the wood… Topping is usually a drastic treatment as far as xylem dysfunction, carbohydrate depletion and loss of dormant buds are concerned…
If a mature tree survives topping, it will form an outer shell of new wood around a dysfunctional core and will therefore require careful management as the new branches increase in girth and weight.’

Many lopped trees become unsafe because the new branches that grow from epicormic buds to replace those lost by the lopping have weak attachment.
There is no mechanism in tree growth that will attach these shoots to the older pre-existing wood.
Failure may also occur as the result of decay expanding into the wood from the lopping wounds.

Dr Lonsdale continues…
‘Topping is rarely an acceptable treatment for trees that are to be retained in the long term and could be regarded as vandalism if done without specific reason…
If a tree of exceptional value could not otherwise be retained in reasonable safety, topping might be acceptable as an alternative to felling.’

Professor Dr Claus Mattheck, the major author of The body language of trees, a handbook for failure analysis[ii], in his ‘Body Language of Trees’ workshops has also recommended topping as a method of managing the decline of veteran trees…
…when other methods do not provide adequate safety.

 

Why should you avoid lopping your trees?

Lopping/topping a tree is arguably the most unethical and detrimental thing you can do to a tree.

When a tree is lopped, most or all of the leaves are removed.
The trees’ food source is removed.
Leaves create and store starches and carbohydrates which the tree consumes and converts into energy.
By removing the leaves, you are removing the main food stores and forcing the tree to rely on reserve stores further down the tree.
These stores are finite and will become depleted if drawn upon too often.

You may wonder how this is different from a deciduous tree losing its leaves in winter.
Deciduous trees draw back all nutrients out of the leaves and stores them behind dormant buds in preparation for the coming spring when the process starts again.

At times, trees do not recover from lopping: they decline or die.
This is particularly true of trees that have been under stress at the time of lopping.

A problem that often occurs with trees that are lopped as a means of management is that the canopy can regrow, look attractive, and not give any indications of the weaknesses within.
It is then difficult to convince interested parties of the weaknesses and the need for further pruning…
…until a failure occurs.

When a tree does actually survive a lopping ‘attack’, the new growth appears in the form of epicormic shoots which are very weakly attached.
The attachment point is only on the surface of the branch. Instead of originating from deep within the branch as with naturally occurring, healthy shoots.

These new, weakly attached shoots grow very quickly and often become heavily laden with foliage.
This, in turn, can lead to branch failure that could have been avoided if correct pruning methods were adhered to in the first instance.

 

Are there acceptable forms of lopping?

There are 2 very specialized forms of lopping that are accepted in the arboricultural community.

These are:
1. Pollarding
2. Hedging

Pollarding

Pollarding is a special form of pruning which involves pruning off regrowth at regular intervals.
This pruning occurs commonly at intervals of 1-2 years.
Extending the pruning interval any longer increases the risk of branch failure.

It is very important to understand that pollarding is only acceptable if a young tree has been specially selected to receive this treatment.

Pollarding can be used to manage the risk associated with a large tree that has been previously lopped.
Although this is commonplace, the ACT Tree Protection Act 2005 prohibits pollarding, which it defines as; the removal of branches of the tree to a previously pruned or lopped point.

It is interesting to note…
Manuka Shops here in Canberra plays host to some rather well known London Plane Trees that have been pollarded successfully for many years.
These are Regulated Trees on public land that have been continually pruned by the ACT Government in direct disregard for the ACT Tree Protection Act 2005.

Trees that are commonly used for pollarding are ornamental species such as:

  • Manchurian Pear
  • Rubinia Mop Top
  • Crepe Myrtle

 

Hedging

It does not occur to most people that hedge trimming is in fact, a form of lopping.

When trimming a hedge you are indiscriminately cutting stems in between branch unions – the very definition of lopping.

All previously mentioned results of lopping occur after trimming a hedge:

  • Vigorous regrowth.
  • Poorly attached unions.

But is considered an acceptable practice because of the way hedges are generally kept.

Hedges are generally pruned/trimmed every 1-2 years, sometimes every 6 months.
It is this frequent trimming that prevents the new shoots from growing out of control and failing under their own weight.

 

What Can Be Done Instead of Lopping?

Trees are genetically programmed to grow to a certain size.
No amount of pruning can change this fact.

You do have options though…

If the tree in question is under regulated size, it is sometimes possible for a regular pruning and maintenance program to be established.
This option allows you to keep a tree that is already established in the area.
But, will require continual attention, most likely on an annual basis.
There will however, be ongoing costs of maintaining the tree at a size suitable for the area.

The other option is a much more permanent alternative.

If the tree is too big for the area in which it is located, or, you are not prepared to commit to the ongoing maintenance of controlling the growth of the tree.
You may want to consider removing the tree completely and starting again.
With a species more suitable to the size limitations you may have.

These limitations apply to the amount of space you have both above and below ground (the right tree, in the right place).

It may be a costly operation, but it will be a one off cost instead of a potentially smaller sum every year or two.

An appropriately qualified arborist can assist you in choosing and sourcing a species of tree that is suitable for the area, the climate, and what benefits you would like to enjoy.

 

If you would like to learn more or feel that you require advice regarding your trees.
Please contact us via email or phone (02) 6161 1800.

 

[i] Lonsdale D 1999 Principles of Tree Hazard Assessment and Management The Stationery Office, Norwich, UK

[ii] Mattheck C, Breloer H, 1994 The body language of trees, a handbook for failure analysis The Stationery Office, Norwich, UK