As an ISA board certified Master arborist, I often get asked about the best way to prune trees. Pruning is an essential part of tree care, as it can improve the health, appearance, and safety of your trees. However, pruning can also cause damage and stress to your trees if done incorrectly or excessively. In this blog, I will explain what structural pruning is, why it is important, and how to do it properly. I will also warn you about a harmful, yet REALLY COMMON practice called lion’s tailing, which you should avoid at all costs.
What is Structural Pruning?
Structural pruning is a pruning technique that aims to develop and maintain a strong and stable tree structure. It involves selectively favoring a single, dominant leader (the main trunk) by suppressing or removing competing leaders or branches that are too large, too long, or poorly attached. Structural pruning also involves thinning out dense clumps of branches and removing dead, diseased, or damaged branches, although these pruning efforts are made toward the end of the canopy on isolated branches, and should not be over-done.
Structural pruning is especially important for young and medium-aged trees, as it can help them grow with a good form and prevent future problems. A well-structured tree has a single trunk with small, well-spaced branches that support the crown. A well-structured tree is FAR more resistant to failure, provides betters clearance, and quite frankly … looks more aesthetically pleasing!
Why is Structural Pruning Important?
Structural pruning has many benefits for your trees, such as:
– Reducing the risk of branch failure and breakage, especially during strong winds, heavy snow, or ice events.
– Preventing the formation of weak or included bark, which can create cracks and cavities in the trunk or branch unions.
– Improving the air circulation and light penetration within the crown, which can enhance the tree’s health and vigor.
– Reducing the need for future pruning or removal of large branches, which can be costly and stressful for the tree.
– Increasing the longevity and value of your trees, as well as the benefits they provide to the environment and the community.
How to Do Structural Pruning Properly?
Structural pruning should be done regularly and gradually, starting from when the tree is young and continuing until it reaches maturity. The frequency and intensity of structural pruning depend on the tree’s species, size, age, condition, and location. Generally, structural pruning should be done every 2 to 5 years, and no more than 25% of the tree’s foliage should ever be removed at one time.
To do structural pruning properly, you should follow these protocals:
1. Identify the dominant leader and the scaffold branches. The dominant leader is the main trunk that extends from the base to the top of the tree. The scaffold branches are the main branches that grow from the leader (off of the trunk) and form the framework of the crown. If there were such a thing as a perfect tree, the leader should be straight and vertical, and the scaffold branches should be smaller than half the diameter of the leader, evenly spaced, and angled at 45 to 60 degrees from the leader.
2. Suppress or remove any competing leaders or codominant stems. These are branches that are similar in size or larger than the leader, and grow parallel or opposite to it. These branches can create weak or included bark, and split the tree in half. To suppress a competing leader, you can reduce its length by cutting it back to a lateral branch that is at least one-third the diameter of the cut branch. To remove a competing leader, you can cut it off at its base or at the branch collar (the swollen area where the branch joins the trunk).
3. Reduce or remove any branches that are too large, too long, or poorly attached. These branches can create excessive weight or leverage on the leader or the scaffold branches, and cause them to break or bend. To reduce a branch, you can use the same technique as suppressing a competing leader. To remove a branch, you can use the same technique as removing a competing leader, or use the three-cut method to avoid tearing the bark. The three-cut method involves making an undercut about a foot away from the branch collar, then making a top cut slightly farther away from the undercut, and finally making a final cut at the branch collar.
4. Thin out any dense clumps of branches or foliage. These can reduce the air circulation and light penetration within the crown, and create a favorable environment for pests and diseases. To thin out a clump, you can remove some of the branches that are crossing, rubbing, or growing inward. You can also remove some of the branches that are growing from the same point on the leader or the scaffold branches, leaving only one or two branches per node.
5. Remove any dead, diseased, or damaged branches. These can pose a hazard to people and property, and spread infection or decay to the rest of the tree. To remove these branches, you can use the same technique as removing a branch, or cut them back to healthy wood.
What is Lion’s Tailing and Why Should You Avoid It?
Lion’s tailing is a harmful practice that involves removing all or most of the interior branches and foliage of the tree, leaving only a tuft of leaves and small branches at the end of the large limbs. This practice gives the tree a lion’s tail appearance, hence the name.
Lion’s tailing is often done by unqualified or inexperienced tree workers, who think that it will make the tree look more attractive, or allow more light and air to reach the ground. However, lion’s tailing can have several negative effects on the tree, such as:
– Creating end-heavy branches, which can lead to instability, bowing, or breakage.
– Exposing the previously shaded branches to direct sunlight, which can cause sun scalding or bark damage.
– Reducing the tree’s ability to produce food and store energy, which can weaken the tree’s health and vigor.
– Stimulating the growth of water sprouts or suckers, which are weak and fast-growing shoots that emerge from the cut branches or the trunk.
– Increasing the tree’s water loss and transpiration, which can make the tree more susceptible to drought stress.
– Reducing the tree’s aesthetic value and natural form, which can lower the tree’s value and benefits.
Lion’s tailing is not a proper or acceptable pruning technique, and it violates the ANSI A300 pruning standards and the ISA best management practices. If you see someone lion’s tailing a tree, you should report them to the local authorities or the ISA. You should also avoid hiring anyone who offers to lion’s tail your trees, as they are likely not qualified or certified to prune trees.
Conclusion
Structural pruning is a vital part of tree care, as it can help your trees grow with a strong and stable structure, and prevent future problems. Structural pruning should be done regularly and properly, preferably in winter, following the ANSI A300 pruning standards and the ISA best management practices. You should also avoid lion’s tailing and companies that perform this toxic pruning style, which is harmful and can damage your trees and reduce their value and benefits. If you need help with structural pruning or any other tree service, with a company which has the knowledge, skills, and equipment to prune your trees safely and effectively, we’d love to help! Just reach out to us here on the website or at the contact info down below!
My Best,
Matt Latham – 409.995.7940
ISA Board Certified Master Arborist #TX-3737B
Member – American Society of Consulting Arborists
Mattlathambcma@gmail.com
www.arboristondemand.org
Sources:
(1) Board Certified Master Arborist Study Materials. https://www.isa-arbor.com/Credentials/Types-of-Credentials/ISA-Board-Certified-Master-Arborist.
(2) Structural Pruning: Part 1 – International Society of Arboriculture. https://wwv.isa-arbor.com/events/conference/proceedings/2013/GILMAN_Structural%20Pruning.pdf.
(3) Structural – Pruning – Landscape plants – Edward F. Gilman – UF/IFAS. https://hort.ifas.ufl.edu/woody/structural-pruning-flash.shtml.
(4) Structural pruning shade trees – Seattle.gov. https://www.seattle.gov/Documents/Departments/Trees/PlantingAndCare/Pruning/GILMAN_Structural_pruning_ISA_symposium.pdf.
(5) Lions Tail Pruning | ISA Texas Chapter. https://isatexas.com/lions-tail-pruning/.
