Is Your Tree Pruning Causing Crown Twist?
When people think about how strong wind affects trees, they often think of the way that wind causes a tree to bend. This is because bending is the most obvious wind effect seen by the eye. But another effect of wind on a tree is twist.
The foliage and branches growing up and out from the trunk of a tree is called its crown. In the presence of wind the tree crown acts like a sail. When the crown is uneven, then the side of the tree with the most crown sees more wind force than the side with the least crown. This uneven force torques the tree and causes it to twist, hence the term crown twist.
Trees can have uneven crowns for a variety of reasons. They tend to grow more branches and foliage towards the sunlight. So in the northern hemisphere, trees often have more foliage on their south facing sides. If two trees have closely grown side by side, then each tree will have less foliage in the direction of the other tree. If one tree falls down, then the other faces the full brunt of the wind with an uneven crown. Uneven crowns can also be caused by disease.
Improper tree pruning
Yet another way for an uneven crown to occur. In addition, sometimes pruning may cause the weight of a tree to be poorly distributed which can make it more susceptible to wind damage.
Trees with uneven crowns will adjust to the twisting effect of wind. This is done when the growth cells grow in a slanted direction. Over time, this slanted growth direction causes a twist in the trunk of the tree.
The problem with crown twist is that any weaknesses that exist within the tree also get torqued. This torque stress will cause small weaknesses such as a small crack to get larger. Cracks can also develop in other weak sections and imperfections. In short, weaknesses get magnified when a tree has crown twist. This can progress to the point where the tree may fail catastrophically during a strong wind storm.
If your tree has an uneven crown, examine it closely for weaknesses such as splits or cracks. If you\’re concerned about crown twist damage or would like professional tree pruning, you can follow along on Facebook and Instagram, or you can contact us here if you have any questions.
