How to Deal With Exposed Tree Roots in Established Yards
The Old House Web
To understand what to do about exposed tree roots in your yard, you first need to properly understand why it's happening. The problem isn't that the roots are emerging from the ground below. In fact, large tree roots, like large trees, are not particularly mobile. What's actually happening is that, over time, the soil that covers the roots gets washed or blown away. While this might seem like a subtle distinction, being aware of what has led to the problem, and why, is important as you craft a solution.
What NOT To Do
There are a couple of things you want to avoid when covering exposed tree roots. One is to dump in a bunch of topsoil and plant flowers or other types of plants around the base of the tree. Yes, it looks pretty--for a while. But you may find it far less appealing a few years down the road, when the tree starts to die. Most of a tree's root network is actually just below ground level, and burying those roots under several inches of soil prevents the tree from getting the water it needs. You also don't want to try and re-seed the area after covering the roots with topsoil, because the same conditions that caused the soil to erode in the first place make it likely that the seed and new soil will likewise wash away before getting established.
A Better Option: Mulch
Arguably the best thing to do is to establish circular mulch beds around the base of your large trees. The reason the grass died in the first place is because as the tree got bigger, the grass underneath it got less light and less water because the grass' root network was competing with the tree's. The resulting sparse growth of the grass made it easier for soil erosion to occur, leading to the exposed roots. Replacing the grass with mulch means you don't have to watch this cycle repeat itself. Also, reducing the size of your lawn saves water.
Depending on the size of the tree, you want the mulch bed to be half to two-thirds the width of the tree's canopy. Some mulch options are:
- Pine straw. This is an ideal mulch because it allows moisture in, and slows down evaporation but doesn't actually absorb any moisture.
- Shredded wood mulch. If you choose this option, you only want to lay it down an inch or so deep because wood mulch absorbs moisture. If you lay it too deep, too much moisture can settle toward the bottom against the tree roots, which can lead to root rot.
- Pine bark nuggets. With this option, you can lay it a bit deeper--say two to three inches--but make sure you remove the old nuggets before replenishing the mulch. Otherwise, the compost that accumulates underneath eventually poses the same risk to the roots as overly deep shredded wood mulch.
If You're Committed to Grass...
You may yet be able to get grass to grow under your tree, but be aware it takes some effort and investment. Begin by cutting the existing grass down to ground level (a string trimmer works best). If the soil is particularly hard, you need to aerate. Add topsoil as you do, and more afterwards, until the exposed roots are covered with about a half-inch of soil. Finally, lay down sod, and water the heck out of it for a couple of weeks until it gets established. And if you haven't already done so, prune the lower branches of the tree(s) so that the new grass gets as much sunlight as possible.