Every year we get a few calls about tree roots in people’s lawns. They cause problems for mowers, they’re trip hazards for kids, and they’re just kind of ugly. The question is, what, if anything, can you do about them?
The first thing to understand is what causes the exposed roots. It’s not that the tree root is bursting out of the ground like some kind of tentacle. Tree roots are not motile. Some trees, like maple, have extremely shallow roots.
If a tree root is exposed to the air, it’s generally because the soil left. And why did the soil erode from around the tree root? Well, typically, it’s because there was nothing holding it there.
We’re all familiar with the problem of grass dying under trees. Not only do they not get enough sunlight, they’re also competing with the tree roots for water. On a hot summer day, a mature oak will absorb up to 100 gallons of water. That’s a powerful thirst.
What Not To Do
When you realize that the exposed roots are caused by erosion, your first instinct will probably be to add topsoil and cover them back up. But not so fast — unless you can get the grass to grow back nice and thick, in a couple of years you’ll be right back where you started, swearing every time you whack the mower blade on them.
Some people will go a step further and create a big bed around the trunk of a tree, maybe plant it full of shade-loving hostas and add a garden bench. But the problem with that is that you’re depriving your tree of water. A good percentage of the rain that falls on trees gets channeled down the trunk. The rest falls on the drip line (part of the reason why tree roots extend as far as they do.) If you plant a perennial bed under your tree, you may have just halved the amount of water it receives. Will it be able to survive on that? Who knows? Do you really want to find out?
What To Do Instead
You’re going to love how simple this solution is. It’s the least work of anything mentioned so far.
Mow down whatever grass is growing under the tree. Raze it to the ground with a weed-whipper. You want bare dirt.
Then, add 1-3 inches of bark mulch. You can use the double-shredded kind if you want, just remember it absorbs more water. Bark mulch will let it all flow through to the roots.
How big a circle of mulch do you want under your tree? Anywhere from half to two-thirds of the total area of the drip-line. Get too close to the edge where it gets more sun and you’ll get a lot more weeds in your mulch.
What’s not to love about this solution to exposed tree roots? It’s less mowing for you, and your yard looks even more put-together and professional.