Two primary factors are considered whenever an arborist assesses trees. One factor is the overall vigor of a tree and the second factor is the tree’s structural integrity. This is why the foundation of urban tree care consists of routine pruning, since it will directly impact these two factors. Pruning is the best way to prevent, correct, treat, and get rid of structural defects. Our arborists at Five Star Tree Services want to go over common defects seen in trees, how they happen, and why pruning can help manage it.
The Structure of Trees
Any people don’t understand why pruning is necessary when it doesn’t happen in a forest. The biggest difference is how trees develop different structures in a forest compared to in an urban environment.
Forest Trees
Trees have had millions of years to master growing in dense forests, where they use phototropism. This is a fancy word for how they respond to growth from sunlight. If you visit a forest, you might notice how the trees have a tall and slender structure. They form like this due to having neighbouring trees so close together, where sunlight can only get down to them from above. This limited and directional light makes it so that there are less opportunities for any structural defects to develop.
Landscape Trees
Now, when looking at trees found in landscapes and urban locations, they typically have few to no trees beside them. This allows sunlight to get to them from all sides, which stimulates growth everywhere. However, although this might seem like a great thing, it is this factor that creates structural defects that can only be remedied with pruning.
Tree Growth Habits
Excurrent
These are the trees that naturally have a uniform, strong, single stem. This can include trees such as pine, aspen, and linden.
Decurrent
These are the trees that have a broad, multi-stemmed canopy. It is these trees which are more prone to structural defects. These trees include Maple, Burch, Ash, Elm, and more. This is why pruning is more necessary for these kinds of trees. However, both kinds of trees can benefit from structural pruning.
Tree Issues
Codominant Stems
This is where there is more than one stem originating from the same spot growing together and are competing to become a primary stem. Inevitably, even if both stems seem equal in structure, there is always a stronger and weaker branch. A codominant stem is especially susceptible to failing. This is caused by rubbing and bark inclusions. An easy solution is to prune the weaker branch away.
There are certain species of trees that are known to grow codominant stems. Sometimes pruning is not able to entirely eliminate all the instances. In this case, the ultimate goal of pruning to treat these trees is to ensure codominance does not affect and from on primary leaders. This means that these codominant stems are not supporting large amounts of the tree’s mass. If you have a mature tree that has codominant stems, you need to make sure it doesn’t grow too big, otherwise it will be too heavy, creating a safety issue with a high chance of failure. It will need reduction pruning to mitigate the risks.
*Side Note: mature trees don’t handle stem removal well. But if you catch codominant stems early on, a stem can easily be removed and the tree will be able to tolerate it.
Dead Branches
It’s completely normal for trees to grow and shed dead branches. Gravity is the main cause for dead branches to fall off a tree. With the unpredictability of this, you will want to have all dead branches pruned before they fall. This is going to avoid injury if a branch were to fall on someone, and also property damage, depending on how large the dead branch is. Pruning dead branches also helps speed up the healing process of the tree. This helps avoid chance for disease, infection, and infestation. You can easily pinpoint dead branches during the spring and summer months, since they won’t have any leaves on them.
Cracked or Broken Limbs
Wind and gravity are the main forces that cause tree branches to fail. Cracks can form and cause breaks. If you notice a branch has a crack, you should remove it immediately. Otherwise, there is a danger of it falling randomly, which can hurt someone or cause property damage. No matter the age of your tree, these branches need to be removed. If there is a wound created that has a large diameter, you will need to keep an eye on it to make sure it doesn’t start to decay.
Rubbing Branches
If there are branches constantly and continuously rubbing together, over time, this is going to form a weak point, leaving it susceptible to failure. This makes it necessary to remove one of the branches before anything bad happens. Select the weaker and less dominant branch to remove.
*Side note: there might be an instance where branch removal is not possible, as the tree won’t be able to tolerate it. In this case, reduction pruning will be needed instead, to lighten the weight of the branches, thus reducing the likelihood of the branches failing.
Branch Stubs
This is what is left behind when a tree branch breaks off. Leaving these can open your tree up to be more susceptible to disease, as it lengthens the healing process. These stubs are removed, no matter the age of a tree. But if significant healing has already taken place, it might be better to leave it than remove it. Since reopening a wound and cutting through new layers of growth can actually impair the healing process.
Branches with Dense Ends & Lions-tailed Trees
Lions-tailed trees can happen both naturally through phototropism and also from bad pruning. Sometimes, aggressive growing branches end up developing elongated branches with most of the leaf growth at the ends. Due to poor pruning, dense branch ends can be formed. The reason it’s called lion’s-tail is from the resemblance of a lion’s tail, where all the secondary and scaffold branches are gone, leaving only the foliage at the ends. Not only does this not look aesthetically appealing, it leaves it more prone to breakage since all the weight is at the ends of the branches and not being distributed evenly.
*Side note: you can correct this with proper and strategic pruning. Arborists can train and restore a tree to have a more uniform growth pattern. This can take years to fix properly. If found in mature trees, this can mean they are past the point of being able to be corrected. In this case, frequent pruning is required or it might need to be removed altogether.
How Five Star Tree Services Can Help
The best time to address any tree defects is when it is young. Having a proper pruning plan is the best way to avoid all defects and allow your tree to be healthy and thrive. Our arborists here at Five Star Tree Services are here to help you with our tree pruning services in Toronto! Give us a call at (416) 990-3355 if you are interested in our services.
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