You’re mowing the backyard and — thunk — the mower blade catches a root. Again. Those thick, snaking roots have been creeping across your lawn for years now, and they’re only getting worse. They trip the kids. They’ve cracked the edge of the patio. And every time you try to push the mower over them, you wince.
So you’re wondering: tree roots above ground, what to do?
You’re not alone. Across Boise, from the North End to Southeast Boise to the older neighborhoods around the Depot Bench, we see this problem constantly. Mature silver maples, cottonwoods, and elms are everywhere in the Treasure Valley, and they’re some of the worst offenders when it comes to surface roots.
Here’s the good news: you don’t have to choose between a beautiful yard and keeping your tree. There are safe, practical solutions that protect the tree’s health while solving the tripping hazard. But there’s one approach that’s surprisingly common, and it can kill your tree outright.
We’ve spent 15+ years helping Boise homeowners figure out the right fix. Let’s walk through your options, starting with the mistake you absolutely want to avoid.
Why Tree Roots Come to the Surface in the First Place
Before you fix the problem, it helps to understand why it’s happening. Tree roots don’t surface just to annoy you. They’re responding to conditions in your soil.
Shallow watering is the number one cause in Boise. Our irrigation culture (running sprinklers for 15 minutes every day) trains roots to stay near the surface where the moisture is. Roots grow where the water is. If the top two inches of soil are always damp and the deeper soil stays dry, roots have no reason to grow down.
Compacted clay soil is another big factor. Much of the Treasure Valley sits on heavy clay. When soil is compacted from foot traffic, construction, or just years of settling, roots can’t penetrate downward. They take the path of least resistance, which is sideways and up.
Erosion plays a role too. Wind, rain, and irrigation runoff gradually wash away topsoil, exposing roots that were once covered. This is especially common on sloped yards and near downspouts.
And then there’s just natural growth. Some species are genetically prone to surface rooting. Silver maples, cottonwoods, willows, Norway maples, and American elms, all common in Boise, are notorious for it. As these trees mature, their roots naturally thicken and push above grade. A root that was buried three inches deep 10 years ago can easily be sitting on top of the soil today.
If your tree roots are sticking up and you want to understand the full picture of what’s happening underground, a tree health assessment is a smart starting point.
The #1 Mistake: Burying Roots Under a Thick Layer of Soil
This is the fix that seems logical but can be deadly for your tree.
We get calls about this more than you’d think. A homeowner gets frustrated with exposed tree roots, rents a trailer, hauls in a load of topsoil, and buries everything under six to eight inches of dirt. Problem solved, right?
Wrong. That thick layer of soil suffocates the tree’s root system.
Tree roots need oxygen. The fine feeder roots, the ones that actually absorb water and nutrients, are concentrated in the top 12 to 18 inches of soil. When you dump heavy soil on top of them, you cut off their air supply. The effect isn’t immediate, which is what makes this mistake so sneaky. The tree looks fine for a season, maybe two. Then the decline starts: thinning canopy, yellowing leaves, dead branches, and eventually the whole tree goes.
We saw this play out in a Southeast Boise neighborhood a few years back. A homeowner (let’s call him Dave) had a 40-year-old silver maple with roots running across half his backyard. He piled about eight inches of fill dirt over the entire root zone. The tree leafed out fine that spring. By the following summer, the canopy was noticeably thinner. By year three, we were called out to assess it. The tree was in irreversible decline. Dave ended up paying for a full tree removal. That tree had been perfectly healthy before the soil was added.
The rule of thumb from the International Society of Arboriculture (ISA): never add more than two inches of soil over a tree’s root zone at one time, and even then, use a light, well-draining mix. Not heavy clay or fill dirt.
Tree Roots Above Ground: What to Do (Safe Solutions That Actually Work)
Now for the good stuff. Here are the approaches that solve the problem without harming your tree.
Mulch the Area (Best Option for Most Yards)
This is the single most effective and tree-friendly solution for surface tree roots.
Spread two to three inches of organic mulch (wood chips, shredded bark, or arborist chips) over the exposed roots. Keep the mulch a few inches away from the trunk itself (no volcano mulching). Extend it out to the drip line if possible.
What this does:
- Covers the roots so they’re no longer a tripping hazard
- Retains moisture in the soil, which actually helps the tree
- Protects roots from mower damage, so no more scalping
- Looks clean and intentional rather than like a problem you’re ignoring
- Breaks down over time, adding organic matter to Boise’s clay soil
A mulch ring is how most professional arborists handle surface roots. It’s simple, inexpensive, and actually good for the tree’s health. You’ll need to top it off every year or two as it decomposes.
A client in the North End, Karen, had a big old elm with roots covering about 200 square feet of her front yard. She’d been fighting them for years, trying to keep grass alive over the roots and losing. We helped her convert the area to a mulch bed, added a clean edge border, and the difference was night and day. No more mowing battles. No more bare patches. The tree actually looked better with the mulch bed framing it.
Convert to a Shade Garden
If mulch alone feels too plain, take it a step further. Create a shade garden bed under the tree using plants that thrive in dry shade, which is basically what you’ve got under most mature trees in Boise.
Good options for Treasure Valley shade gardens include:
- Hostas (with supplemental water)
- Sweet woodruff
- Coral bells (Heuchera)
- Epimedium
- Native Idaho fescue as a ground cover alternative to lawn grass
Plant between the roots. Don’t dig into or cut them. Use a hand trowel and work carefully. Add two inches of compost-amended topsoil in the planting pockets, not over the entire root zone.
This approach works especially well for how to cover tree roots in yard situations where the root area is large and visible from the street.
Add a Thin Layer of Topsoil (Carefully)
If you want grass to grow over the roots, you can add soil, but you have to do it right.
The key limitations:
- No more than two inches of topsoil at one time
- Use a light, loamy mix, never heavy clay or fill dirt
- Blend it gradually: work the soil into the existing grade rather than dumping it on top
- Wait at least a full growing season before adding another thin layer
- This works best for minor root exposure, roots that are just barely above grade
This method won’t work for large, heavily exposed roots. If the roots are sitting three or four inches above the surrounding soil, two inches of topsoil isn’t going to cut it. For those situations, mulch or garden conversion is the better call.
Raise Your Mower Height
Sometimes the simplest fix is the best one. Set your mower deck to its highest setting, usually three to four inches. This won’t eliminate the tripping hazard, but it stops the mower from scalping roots and damaging both the roots and your blade.
This pairs well with the mulch approach. Mulch the worst areas, raise the mower for the rest. Practical and low-cost.
When Root Pruning Is (and Isn’t) an Option
You might be wondering: can you just cut the offending roots?
Sometimes, yes. But it’s risky, and here’s why.
Cutting a tree root is essentially amputating part of the tree’s support and nutrient system. According to ISA best management practices, root pruning should only be considered when:
- The roots are small (under two inches in diameter)
- They’re located well outside the drip line, far from the trunk
- They’re not structural roots that anchor the tree
- The tree is otherwise healthy and well-established
Root pruning is dangerous when:
- The roots are large structural roots (over three to four inches in diameter)
- They’re within the critical root zone, generally the area inside the drip line
- The tree is already stressed, leaning, or in decline
- Multiple roots on the same side would need to be cut (this destabilizes the tree)
A good rule: if you’re not sure whether a root is safe to cut, don’t cut it. A certified arborist can evaluate which roots are structural and which can be safely pruned without compromising the tree’s stability or health.
We had a situation in the Bench area where a homeowner, Tom, cut three large roots on the south side of a cottonwood because they were lifting his fence. The tree survived, but it developed a noticeable lean toward the south within two years. We ended up recommending removal because the tree had become a safety risk over his neighbor’s property.
If you’re dealing with surface tree roots near structures, give us a call before you grab the chainsaw. A quick assessment can save you from a much bigger problem down the road.
When Exposed Roots Signal a Bigger Problem
Most of the time, surface roots are just an aesthetic and practical nuisance. But occasionally, they’re telling you something important about the tree’s health or stability.
Watch for these warning signs:
- Roots lifting on one side only. If roots are heaving upward on one side of the tree while the opposite side shows soil separation or cracking, the tree may be destabilizing. This is especially concerning after heavy wind events or during our spring freeze-thaw cycles in Boise.
- Roots that are decayed or crumbly. Healthy roots are firm. If the exposed roots are mushy, dark, or breaking apart, the tree may have root rot, often caused by overwatering or poor drainage.
- Circling or girdling roots. Roots that wrap around the base of the trunk can strangle the tree over time. This is common in trees that were planted too deep or left too long in nursery containers.
- Sudden root exposure after a storm. If roots that were previously underground are suddenly visible after wind or heavy rain, the tree’s root plate may have shifted. This is a structural emergency.
If you notice any of these signs, don’t wait. A tree with compromised roots can fail without warning. Contact us for a root and stability assessment, especially if the tree is near your home, driveway, or a neighbor’s property.
The Deep Watering Connection: How Boise’s Irrigation Habits Make Roots Worse
Here’s something most Boise homeowners don’t realize: your sprinkler schedule might be the reason your roots surfaced in the first place.
The Treasure Valley has a strong irrigation culture. Many homeowners run sprinklers daily, or even twice a day during July and August. Short, frequent watering keeps the top few inches of soil moist while the deeper soil stays bone-dry.
Roots follow moisture. When water is always at the surface, roots have no incentive to grow down. They spread laterally through that top layer of moist soil, and eventually they outgrow it and break through.
The fix: deep, infrequent watering.
- Water your lawn and trees two to three times per week instead of daily
- Run each zone longer, long enough for water to penetrate eight to 12 inches deep
- Water early in the morning to reduce evaporation (Boise’s dry summer air can evaporate surface moisture fast)
- For established trees, consider using a soaker hose or deep-root watering probe a few times per month during peak summer
This won’t reverse roots that have already surfaced; once they’re up, they’re up. But it can slow the progression and encourage new root growth at deeper levels. It’s also just better for your tree’s overall health, especially during Boise’s hot, dry summers when temperatures regularly push past 100 degrees.
The University of Idaho Extension has excellent resources on proper watering for Treasure Valley landscapes if you want to learn more.
A Practical Decision Framework for Tree Roots Above Ground: What to Do Based on Your Situation
Every yard is different. Here’s a quick guide to match the right solution to your specific situation:
Roots are barely visible, just catching the mower: Raise your mower height. Add one to two inches of topsoil. Monitor annually.
Roots cover a moderate area, causing tripping hazards: Apply two to three inches of mulch. Create a defined mulch ring or bed. This solves 80% of cases.
Roots cover a large area, grass won’t grow: Convert to a mulch bed or shade garden. Stop fighting a battle you can’t win. This usually looks better than patchy grass anyway.
Roots are lifting hardscape (sidewalks, patios, fences): Call a certified arborist. Selective root pruning may be possible, but it needs professional evaluation. Sometimes strategic trimming to reduce canopy weight can help slow root expansion.
Roots are heaving on one side, tree is leaning: This is a potential safety issue. Get a professional assessment immediately.
Conclusion
Exposed tree roots are one of those problems that look simple on the surface, but the wrong fix can cost you a mature, valuable tree. We’ve seen it happen too many times in Boise neighborhoods.
The good news? The right solution is usually the easiest one. A few inches of mulch, a well-planned garden bed, or a change in your watering habits can solve the problem without risking your tree’s health.
The most important thing to remember: don’t bury those roots under a mountain of soil. It’s the most common mistake we see, and it’s the most damaging.
If you’re unsure about the best approach for your specific tree, or if those exposed roots are making you nervous about stability, we’re happy to take a look. A quick on-site assessment gives you a clear plan and peace of mind. Reach out to Boise Tree Pros and we’ll help you figure out the right move.
Your tree has probably been in your yard longer than you have. It’s worth protecting.
Frequently Asked Questions
Is It OK to Cover Exposed Tree Roots With Dirt?
You can add a thin layer, no more than two inches, of light, well-draining topsoil. But never pile on heavy soil or fill dirt in thick layers. Anything over two to three inches can suffocate the feeder roots and slowly kill the tree. For most situations, mulch is a safer and more effective option than soil.
Will Cutting Exposed Tree Roots Kill the Tree?
It depends on the size and location of the roots. Cutting small roots (under two inches in diameter) far from the trunk is generally low-risk. Cutting large structural roots, especially within the drip line, can destabilize the tree or cause decline. Always consult a certified arborist before cutting any root larger than your thumb.
Why Are My Tree’s Roots Growing Above Ground?
The most common causes are shallow watering habits, compacted clay soil (very common in the Boise area), natural erosion, and species genetics. Silver maples, cottonwoods, willows, and elms are especially prone to surface rooting. Switching to deep, infrequent watering can help slow future root surfacing.
Can Surface Roots Damage My Home’s Foundation?
Tree roots rarely crack or break foundations directly. They’re not strong enough to push through intact concrete. But roots can exploit existing cracks, grow into gaps, and contribute to soil moisture changes that cause shifting. If you have large roots growing toward your foundation, a professional assessment can determine the actual risk level. Learn more in our guide on tree roots and foundation concerns.