BLOG: Why Trees Blow Over in a Storm!

The south metro was hit hard recently with a storm that knocked over many trees. So what causes one tree to blow over while other ones near it are OK? And, are there things you can do to reduce the chances of losing big, beautiful, mature trees?

I was thinking that since we got so much rain in the last storm, that a big factor in trees blowing over was ground saturation—that a tree would just be uprooted since the soil was so wet and loose. But still, why is it that a whole group of trees in the same area would not be blown down?

I know a master arborist, Mark, so I called him to make sense of it all. What he told me was kind of surprising.

Turns out some trees are more susceptible to being blown over when the soil is saturated, but most are not. The big factor is the integrity of the root system.

Trees such as tall, lean evergreens like spruces and fir are more likely to get blown over when the ground is real wet, even if their root systems are good – they’re just not able to withstand a strong, sustained wind.

But most trees blow over because their root systems are compromised, said Mark. They’re simply not properly attached to the ground. This is usually the case when the roots are diseased, or if the tree was planted in an area with poor drainage, poor quality soil, poor soil volume, or compacted soil.

How can you tell if the roots of a tree are diseased? If the canopy of the tree is not as dense as it should be or the color and size of its leaves are not normal, this could mean that the roots could be diseased. In many cases it’s possible to treat a diseased tree.

We have a very mature ash tree in our front yard. I know that our soil is clay not far beneath the surface. When Mark mentioned drainage and soil quality, I thought our clay could be a potential problem. But he said that clay can be fine for a tree, as long as it also has a good soil mixture and good soil volume with lots of organic matter, and good drainage.

However, clay can be a bad soil for certain species of trees. Wow, tree stuff can get complicated! The best way to determine if a root system is healthy is to have a licensed arborist inspect the trees on your property. We’ve had tree trimming work at our house done by S&S Tree, which is how I met Mark, but I never knew how valuable an arborist can be.

Another factor, of course, is safety. An uprooted tree is a worst case scenario, but next to that is a big limb or big branches crashing down – they’re a lot heavier than you think. The best way to make mature trees safer is to have them professionally trimmed every two or three years. We made the mistake of having some “door knocking” freelance guys do this one year … not pretty, and that’s why we called in an actual pro company the next year.

It’s sad to lose a big, beautiful tree. Even sadder if someone gets hurt. Sometimes a storm will blow down even the healthiest of trees, but at least there’s something you can do to minimize the chances that you’ll lose a tree in the next summer storm.