As professionals in the tree and arboricultural industry, we are often called upon to provide guidance on whether a tree is ready for pruning or not. We consider it a privilege to be entrusted with helping make this decision and always do our best to do it with integrity and honesty. Oftentimes we will go out to look at a tree that the client is concerned about and find that it can actually go several years before being pruned and no urgency is needed. Using our knowledge of how trees grow and our experience with pruning them over the years we look for some indicators to determine when it’s time for pruning.
9 Signs That Aid Us, Arborists, in Determining If a Tree Is Ready for Trimming:
1. Broken Branches
If your tree exhibits broken branches in the upper canopy or if any branch, regardless of size, has fallen since its last pruning, it is likely in need of pruning. When a branch breaks it can indicate one of the following: Structural issues could be present that need correcting. There are branches throughout the canopy that have more weight than they can support and are beginning to fail.
2. Large Dead Branches
If your tree has dead branches that, if they were to fall, pose a risk of causing harm to a person, then it is time to prune it. Smaller dead branches can develop normally when there is insufficient light in the canopy and these are usually harmless. The larger branches are usually a health issue and should be pruned out to prevent a risk to people underneath. Its health should also be assessed, because large dead branches are usually an indicator that the tree is undergoing environmental stress and if changes are not made it could eventually die.
3. Drooping Branches
Tree branches naturally grow upwards or at least have a slight upward growth pattern. Some trees naturally have a drooping or weeping growth pattern, so those are the exception to this rule. When they start to grow downwards or begin to develop a sharp angle towards the ground then the branches are too heavy. When they are heavy and at this stage, the pruning needed is focused on reducing weight and encouraging the branch to grow upwards again. Often this is something that can be noticed before a large limb breaks. These trees are usually the first to break branches in a large wind storm.
4. Dense Canopy
When a canopy is dense that is a good indicator for health. Lots of leaves are good and will help supply the tree with food and nutrients. It can however pose a structural issue to some trees.
A dense canopy can catch the wind instead of allowing it to flow through the canopy. When it is very windy this can cause a lot of stress on the roots and branches and contribute to failure. This is mostly the case for evergreens in the winter time. Caution must be taken not to over prune because this can cause the problem to get worse. The branches also protect each other from the wind and elements and you do not want to leave them too exposed. Filtered light coming through the canopy is the goal.
A dense canopy can harbor insects. Insects prefer shade and dark environments. Allowing filtered sunlight through the canopy will naturally detour insects from harboring in the canopy. Some common insects that like this environment are: aphids, scales, mites, and white flies.
A dense canopy can cause branches to die back. Branches in the canopy need light and when the inner branches and foliage do not receive light as the tree grows they usually will die back. This is not a health issue but it can be a problem when the lower branches provide privacy and improve the aesthetics. Pruning to allow filtered light will ensure the inner and lower limbs receive adequate light.
When a tree grows heavily to one side it can cause the risk of large branches to fail due to the excessive weight. Limbs that extend beyond the rest of the canopy are exposed to the elements and are more vulnerable to weather and wind impacts.
When an imbalance is developing, the overall aesthetic can be affected and the natural rounded and balanced shape will be lost. This might require heavy and excessive pruning to correct if too much time lapses between pruning cycles.
An imbalanced canopy can also put excess strain on the roots. If a tree grows heavily to one side, the added weight increases the likelihood of failure in that direction, especially if the roots are compromised.
5. Imbalanced Canopy
If you notice that the canopy of your tree is growing heavily to one side, then it is ready for a prune.
6. Trees Under Power Lines
Often trees under power lines are pruned by PG&E Contractors. Usually only the parts within 10 feet of the high voltage lines are pruned and the other parts are neglected. This pruning approach may result in unattended limbs for many years until a failure eventually occurs.
The type of pruning often performed to clear power lines is V pruning. This clears the center and leaves the outer limbs to grow untouched. These other limbs are more prone to failure due to the type of structure being developed.
It is the responsibility of the homeowner to perform the needed pruning to reduce weight and encourage structural integrity because the utility companies are only focused on the areas near the wires.
If this type of pruning was performed on your tree and you have not pruned it within the last 5-7 years then it is most likely ready for a prune.
7. Over 7 Years Since Last Prune
If your tree is in close proximity to people or structures and the aim is to optimize structural integrity and minimize risk, then it’s advisable to prune the tree approximately every seven years.
In our experience, when trees are left to grow on their own for 7 years or more, they are more likely to be at risk of failures.
Risk tolerance is a factor when considering the frequency of a prune. If a tree is growing over a home, in an area where people often gather, or a focal point of the yard, then pruning should be performed more often to ensure its safety. If the tree is in an open field where human traffic is rare, you may be able to postpone pruning for up to ten years, although there’s an acknowledgment that a branch failure could occur unpredictably. However, in such a setting, the likelihood of the falling branches posing a risk or causing harm is minimal.
8. High Risk Trees
In Northern California, certain tree species are identified as high-risk, based on our extensive tree management experience. These species are particularly prone to failure. If you have one of these trees, we advise pruning at the following intervals:
Every 3-5 years: Fruitless pear, Chinese elm, Palms, Chinese pistachio, Hackberry, Ash, Liquid amber, Eucalyptus, and several others.
9. Improperly Pruned
If your tree was pruned improperly, the tree may be at more risk and may require immediate attention to correct.
Lion tailing: If your tree was heavily thinned and the foliage was left only on the outer limbs, then the branches are at risk of breaking. This pruning forces the growth towards the end and prevents the branch from developing thickness to support the weight. Pruning may be needed to reduce weight and canopy in size.
Topping: If the tree was topped in the past and it has not been pruned in many years, then it may also be at risk of failing. When the growth returns, it is weakly attached and is more prone to failing. Especially when the new limbs are developing length and weight.