If you have large-growing trees in your yard, you might find yourself having to deal with surface roots. Surface roots are problematic because they make lawn maintenance challenging underneath shade trees. Additionally, large tree roots become a trip hazard. They can also disrupt sidewalks, causing them to crack. Finally, they’re just unsightly! So, how do you deal with surface roots without jeopardizing the health of your tree? What actually causes them? We’ll answer these questions and more!
What Causes Surface Rooting?
Some trees are simply predisposed to having shallow roots. This includes Norway Maples, Red Maples, Silver Maples, Willows, aspens, Pin Oaks, and Beeches. And any large tree can develop surface roots after a certain age. It’s just how they grow. Still, other factors play a part.
Poor soil quality
For the most part, the majority of trees’ roots are found within the top 12 inches of soil. Contrary to popular belief, tree roots usually do not grow very deep unless they are in loose and sandy soil. Surface rooting is most common in compacted or clay-based soil often found in urban areas. When the roots within the first few inches of soil get large enough, they break through the surface. Gradually, rain and wind erode the soil around them, further exposing them.
Lack of oxygen
Roots need oxygen. In compacted soil, they must grow up to the surface in order to get enough oxygen to keep the tree alive. In many cases, trees with surface roots are struggling to breathe and are doing their best to adapt to an environment that is less than ideal.
So, What can i do to deal with surface roots?
If you have a tree or trees with surface roots, there are a couple of things you can do.
Don’t cut roots!
Don’t cut the offending roots, no matter how tempting it is. Cutting them can provide an easy entry point for diseases and harmful insects. It can also negatively impact a tree’s stability, making it more likely to fall over in a bad storm. Finally, cutting roots can kill thousands of tiny “feeder roots” that allow the tree to absorb water and nutrients. This can lead to dieback in the canopy or complete death of the tree.
Topdress around the base of the tree
To help deal with surface roots, mix equal parts topsoil and compost. Then, apply two inches of the mixture around the base of the tree. Sow the area in late summer with shade-tolerant grass seed, keeping it well-watered. If the roots are still prominent within a year, you can add another two inches of the mixture and reseed. Never add more than four inches of soil to the area beneath an existing tree! Otherwise, you risk suffocating it.
Instead of grass, you could plant drought-tolerant groundcover under the tree. This would save you the trouble of having to mow in that area—or, you could mimic nature and consider using moss as groundcover!
Your best bet is to put down four inches of mulch—preferably wood chips—underneath the tree. This will help level out the area while keeping roots cool and moist and allowing them to breathe. Don’t put down more than four inches, though, and don’t pile mulch against the trunk.
Avoid trees with shallow root systems
If you have compact or clay soil, your tree will inevitably have some surface roots. Still, some trees are way more likely to develop them than others. Steer clear of notorious surface rooters like aspens, beeches, river birches, certain maples (red, silver, sugar, Freeman, and Norway), pin oaks, spruces, sweetgums, tulip poplars, and willows. These trees have inherently more shallow roots and are more likely to pose a problem in your landscape.
Choose trees with deeper root systems
Some trees have deeper root systems. These trees will make much better options in your landscape and are way less likely to develop surface roots. Black gum, blue atlas cedar, ginkgo, golden rain tree, horse chestnut, certain oak varieties (red, Regal Prince®, swamp white, white, and willow), planetree, yellowwood, and zelkova are some of the best options.
Consider a smaller tree
Trees that mature at under 30 feet tall will usually not have roots large enough to cause major problems. If size is not as important to you, consider varieties like cherry trees, dogwoods, magnolias, mimosas, Japanese maples, paperbark maples, redbuds, and lilac trees, just to name a few.
Don’t plant your tree too deep
Planting your tree deep within the soil won’t actually prevent surface roots. On the contrary—we actually recommend planting trees two inches above grade (but make sure the rootball isn’t exposed, or it could dry out and be more vulnerable to winter damage).
Give trees room to grow
Give your tree space if there is pavement nearby. Large-growing tree should be planted at least six feet away from paved surfaces. If you want to plant your tree between a sidewalk and a street, make sure the planting spot is at least eight feet wide with no utility lines overhead. Otherwise, choose a smaller variety. Keep in mind: some cities have restrictions and specific guidelines on planting, so you’ll want to check with your local forestry department before planting.