The crown of a tree is the uppermost part, which, if left unkempt, will have several negative effects on the tree. In this article, I’ll be discussing crown pruning, lifting, reduction, and thinning.
What is Crown Thinning?
This is a type of pruning method mainly practiced on hardwood trees. It is the pruning of selected stems and branches to create pathways for sunlight and air to reach all parts of the tree’s crown.
Why Crown Thin A Tree?
As I just mentioned, crown thinning is meant to create a passage for sunlight and air so all parts of the tree’s crown can access them.
When a crown is thinned, the overall shape of the tree is not altered.
Any branches that rub against each other or are crossed are removed during crown thinning. After which, the tree is pruned, so the crown density will be reduced.
Remember, the tree’s natural shape will be retained.
What parts do I thin first?
Look for items that are narrow and V-shaped and should go first. This is because they form an included bark.
An included bark will form a wedge when two stems grow at sharp angles. These wedges hinder strong attachments of stems and would lead to cracks in the area below where the branches meet.
Cutting off one (or more) of such problematic stems will allow the others to be free.
How do I avoid unnecessary stress on my tree?
If you want to spare your tree the stress of facing an excessive production of epicormic sprouts, don’t remove more than one-quarter of the living crown at a time.
If removing more is unavoidable, then be sure to do it over the coming years, and not immediately.
What Is Crown Reduction?
Crown reduction is a lot more extensive than crown thinning.
It is used to achieve the following:
- Reduce the weight of dangerous branches
- Restore the balance of a tree after it takes some damage (maybe from a storm)
- Prevent the tree from obstructing a pathway or building
- Prevent trees from tangling in-between power lines or telephone lines
What tree work is recommended to reduce the chances of storm damage?
Crown reduction is not meant to reduce the chances of a tree tilting over from a storm. However, it’s the recommended method for minimizing storm damage to a structurally sound tree.
You can choose crown reduction as an option when you find the root of a maturing tree to be decayed (or is decaying), and it poses a threat to the people and property around its immediate surroundings.
How is crown reduction achieved?
The aim here is to cut so that the foliage on the outer edge of the new canopy is not tampered with.
This means that after the prune, the cuts wouldn’t be obvious to an onlooker.
A list of techniques that are not suitable for tree size reduction include:
- Rounding over
This is because they alter the tree’s natural structure and they can expose the tree to decay.
I want a smaller tree; how much foliage can be removed?
If you plan to remove up to 30% of your tree’s foliage, then it is recommended that you split the job into two phases. I advise each pruning phase is done 12 months apart.
If it is dome this way, your tree will not experience unwanted sprouting. Also, there will be minimized starch removal from the tree.
If you want to reduce with drop-crotch cuts, then you can trim the branches that are extended beyond the other surrounding branches.
By doing this, the tree will reduce in size, but the original shape will be maintained.
The longest parts of the main branch will be trimmed down to the size of a smaller lateral branch. This smaller branch should be large enough to take up the role of the branch that was cut.
If you cut back a branch that is too small, your tree may experience excessive sprouting and decay.
A reduction of about 15% to 20% is ideal. Anything more than that is dangerous for the tree.
Crown reduction is a technique that takes up time. Many arborists consider it an art, as opposed to being tree science. A lot of skill is required to carry out a proper crown reduction, so calling a professional to get it done is your best bet.
What Is Crown Lifting
Crown lifting is the removal of the lower branches of a tree, which is done to increase the space between the ground level and the other branches.
This can be done for many reasons, including clearing sightlines, allowing for a better view, clearing a walkway, or allowing light to reach the ground.
When you lift the crown of a tree, you can achieve the following –
- Create space around the ground of a tree
- Create better visibility for signs
- Allow more light penetration
- Free the lower trunk of branches
As for damage, this type of pruning does very little to the tree compared to reducing the size of the canopy. Achieving this over a few years is my recommendation.
What is the Potential Damage of Crown Lifting?
If there are too many lower trunk branches cut off at the same time, then the trunk itself may become seriously injured.
Below are a few complications that could arise from cutting many low branches at once –
- Discolored wood
- Decay and rot within the trunk
- Sunburn in the lower trunk
- This can lead to epicormic growth (forcing the tree to grow taller)
What is the Ideal Solution for Crown Lifting?
As a rule of thumb, about half of the foliage should come from branches located at the lower two-thirds of the tree.
Some of the major branches at the lower half of the trunk must be left untouched.
It is recommended that you leave smaller branches at the lower trunk untouched for one year (maybe more), after cutting the large branches. This is because they help reduce injuries caused by sudden exposure to sunlight.
They act as shades, which helps the pruning wounds seal faster.
Thin or drop-crotch cut the biggest branches found at the lower end of the tree trunk. Leave the smaller ones untouched.
By doing this, you will be providing enough clearance for about 12 months since the branches will usually spring upwards of branches from the tips that have been removed.
If required, you can cut all the branches back to the trunk later on, maybe one or two years after.
What if the lower branches are large in Diameter?
Cutting lower branches that are wide in diameter might promote trunk decay. The best bet here is thinning them by reducing their lengths with drop crotch cuts, as opposed to cutting them off completely.
Doing this will ensure their growth is slowed, and the trunk will eventually grow larger than the thinned large-diameter branch.
During this period, the tree will form a branch defense zone, so the risk of trunk decay will be reduced if the branch is cut.
When lifting the canopy, it is important to carry out any other form of necessary structural pruning to normalize any defects. It would be wrong to cut off low branches without attending to the tree’s structural problems.
What You Will Need To Prune Your Tree
Crown pruning is a job that requires some skill, patience, and experience. Without these three, you can never get the job done right.
But wait, there’s one more factor you need to consider before you embark on any pruning, and that’s the tools you will need.
These are listed below.
Pruning saw: This saw is meant to cut the intended branches. They are very sharp and lighter in weight than the regular chainsaw.
Pole saw: This will come in handy when you want to cut branches high up the tree’s canopy. It is meant for areas in the tree your arms can’t reach.
Pruning shears: This will be used to trim up foliage on the branches of the lower canopy. They are meant for cutting smaller branches.
Other Items You Will Need For Crown Pruning
Besides the cutting tools, there are other items you will need.
They are listed below.
Ladder: To reach high branches.
Safety helmet: To protect your head from falling branches.
Work boots: To protect your feet from broken pieces of a tree branch, which can pierce a person’s feet.
Before you attempt to prune the crown of your tree, be sure the situation is safe.
If the branches are caught up in-between power lines, then DO NOT attempt it. Call the relevant authorities and personnel to handle such a situation.
I trust this article on crown pruning, reduction, thinning, and lifting has been of great help.
Take care & stay safe!