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Tree roots are easy to ignore because most of the root system is hidden underground. But when roots begin popping up in the lawn, interfering with landscaping, lifting pavement, or growing into a damaged sewer line, they can quickly become a bigger problem.
Contrary to a common misconception, most tree roots don’t extend dozens of feet straight down. The majority grow relatively close to the soil surface and spread out beyond the tree’s canopy. And after a tree is cut down, its roots generally die and decompose eventually, although some species can continue producing sprouts from the stump or roots for quite a while.
If the tree has already been removed, physically removing the stump and problem roots is usually the fastest and most reliable solution. Smaller roots can often be handled by hand, while extensive root systems may need professional stump and root removal. If you’re looking for a slower DIY option, Epsom salt is also commonly used to dry out a stump, though there’s not a ton of real evidence for its effectiveness at killing an entire root system.
If you’re wondering how to destroy tree roots without using harsh herbicides, the best approach depends on whether the tree is still standing, the size of the roots, and where they’re growing.
Why You Might Need to Kill Tree Roots
You shouldn’t need to remove every visible tree root. In fact, cutting major roots from a healthy, standing tree can weaken or destabilize the tree. Choosing the best trees for your backyard based on the available space, mature size, and proximity to hardscaping can help prevent root problems in the first place. But when an existing tree is growing in a location that doesn’t give its root system enough room, getting rid of tree roots that interfere with landscaping, pavement, or underground utilities may become the best way to go
Problem tree roots can:
- Interfere with landscaping. Large surface roots make mowing difficult and can prevent grass and other plants from growing evenly.
- Create trip hazards. Raised roots can become hazards in lawns, paths, and other frequently used areas.
- Lift sidewalks, patios, and driveways. As roots get thicker, they can contribute to displacement and uneven hardscaping.
- Enter sewer lines. Roots can grow through cracks, loose joints, and other defects in sewer pipes, eventually contributing to serious clogs.
- Interfere with structures. Large roots growing near shallow foundations, retaining walls, and other structures can make existing soil or structural problems even worse.
Roots found inside a sewer line are particularly important to address. However, roots generally enter pipes through an existing crack, failed joint, or other opening. Killing the nearby tree or roots alone will not repair the damaged pipe.
3 Ways to Kill Tree Roots in the Ground
Before removing roots: If your goal is to kill a tree from the roots while the tree is still standing, talk to an arborist first. Cutting or damaging structural roots can make a tree unstable before it dies, creating a serious falling hazard. Also call 811 before substantial digging to have underground utilities marked.
1. Cut and remove smaller roots.
If the tree or stump has already been removed and only a few troublesome roots remain near the surface, cutting them out manually may be the simplest solution. This approach requires some digging and physical effort, but it removes the main problem immediately without having to put salt or herbicides into the soil.
For a standing tree, limit DIY work to small roots well away from the trunk. Roots several inches thick or roots close to the tree’s base should be evaluated by an arborist before cutting.
To remove a small tree root:
- Dig around the root with a shovel until you expose enough of it to work comfortably.
- Clear soil from both sides so you can see where you will make your cuts.
- Use sharp loppers for small roots or a pruning saw or reciprocating saw for larger ones.
- Make clean cuts rather than ripping or tearing the root.
- Remove the severed section from the soil.
- Backfill the hole with soil and repair the surrounding lawn or landscaping.
If the root belongs to a tree that has already been removed, the portions left in the ground will eventually decay.
Tried-and-True Advice
“When we bought our house the front yard had one beautiful tree and one stump. After removing the stump there were still quite a few roots, so we took an unconventional approach: We built up a fire pit [over the roots], and for two years we had bonfires there. After two years, between the fire and the natural decomposition process, it was easy to just lift out the remaining dead roots and repair the lawn. I live in Minnesota where bonfires are permitted on the front lawn so it wasn’t an issue.”
—Amber Guetebier, Contributing Writer
2. Dig out the larger roots and root ball.
When a stump has already been removed but large roots are preventing you from landscaping, building, or leveling the area, digging them out provides a more complete solution.
Start by excavating around the largest visible roots with a shovel or mattock. Cut manageable sections with a pruning saw or reciprocating saw as you expose them, then pull those sections from the ground. Continue working toward the remaining root crown until enough material has been removed for the intended use of the area.
Removing an entire root system by hand becomes difficult quickly, particularly with large, mature trees. A tree service can excavate the stump and main root ball with specialized equipment. Stump grinding is another option, but keep in mind that a grinder usually removes the stump and some wood below grade rather than pulling out the entire root system.
If your goal is to build a patio, foundation, driveway, or another permanent structure where the tree once stood, complete stump and root removal may make more sense than waiting for the roots to decay.
3. Use epsom salt on the stump.
Epsom salt, or magnesium sulfate, is commonly recommended as a DIY method for drying out a tree stump and its remaining roots. Concentrated salts can interfere with a plant’s ability to take up water, but research specifically demonstrating that Epsom salt reliably kills an entire tree root system is limited. For that reason, consider this a slow DIY method rather than a guaranteed substitute for physical removal.
To try this method:
- Use a drill fitted with a large bit, around 1 inch in diameter, to make several holes in the top of the stump. Drill the holes several inches deep and space them a few inches apart.
- Fill the holes with Epsom salt.
- Add just enough water to moisten the salt without flushing it from the holes.
- Cover the stump with a tarp to keep rain from washing away the salt and to block sunlight from any new growth.
- Check the stump periodically and refill the holes if necessary.
- Remove any suckers or shoots that appear. Preventing new foliage from developing keeps the remaining roots from replenishing their stored energy.
This is not a quick process. Depending on the species and size of the stump, drying and decomposition can take months or longer.
What about rock salt?
Rock salt, which is mainly sodium chloride, can also damage and kill plant tissue. But it’s much harder on the surrounding soil and can injure nearby grass, trees, and landscaping. Excess sodium can remain in the soil and make it difficult for plants to grow afterward.
For that reason, we don’t recommend spreading rock salt around tree roots or saturating the surrounding soil with it. If you use any type of salt treatment, keep the material contained within holes drilled into the stump and away from children, pets, nearby plants, and waterways.
How to Remove Tree Roots in a Sewer Line
Tree roots in a sewer line should be treated differently from roots growing through the lawn. Roots generally enter a sewer pipe because the pipe already has a crack, loose joint, or other defect that gives the roots access to moisture and nutrients. Removing the roots clears the immediate obstruction, but repairing the pipe is what prevents the problem from returning.
1. Have the sewer line inspected.
Recurring slow drains, gurgling fixtures, or sewage backups can indicate a blockage, but they don’t prove that roots are responsible.
A plumber can feed a sewer camera through the line to identify the obstruction and locate damaged sections of pipe. This is particularly worthwhile before attempting repeated drain cleaning on an older sewer line.
2. Clear the roots.
Plumbers commonly use a powered sewer auger fitted with a cutting head to cut through roots inside the pipe. Depending on the pipe material, condition, and severity of the blockage, hydro jetting with high-pressure water may also be used to remove roots and accumulated debris.
Avoid trying to solve a serious root intrusion by pouring rock salt, Epsom salt, vinegar, or other DIY mixtures down the drain. Even if the treatment damages some roots, it does nothing to repair the opening that allowed them into the pipe.
3. Inspect the pipe again.
Once the blockage is removed, a second camera inspection can reveal cracks, displaced joints, collapsed sections, or other damage that was previously hidden by the roots.
4. Repair the damaged sewer line.
The permanent fix may be a localized pipe repair, trenchless pipe lining, pipe bursting, or replacement of part of the sewer line, depending on its condition.
Simply removing or killing the tree is rarely the complete solution. If the damaged pipe continues leaking moisture into the surrounding soil, roots from other nearby trees and shrubs may eventually find the same opening.
How much does it cost to remove tree roots?
The cost to remove tree roots depends largely on the size of the stump and root system and how difficult the area is to access. Removing a single tree stump typically costs about $100 to $150, while additional stumps may cost around $50 each.
If you also want the stump ground down and the remaining roots killed, expect to pay an additional $100 to $400 on average. The final price depends on factors like the age and size of the stump, the extent of the root system, and the condition of the surrounding ground.
Roots that have grown into a sewer line are a different issue and may need a plumber or sewer specialist to clear the blockage and inspect the pipe for damage.
FAQ
Q. Will salt kill tree roots?
Yes, but watch out. High concentrations of salt can injure or kill plant roots by interfering with their ability to absorb water. Rock salt is particularly damaging because the sodium can also degrade soil conditions and harm surrounding plants.
Epsom salt is commonly recommended as a less damaging way to dry a stump, but there is limited research to show that it reliably kills an entire root system. Physical removal is still the most dependable option when you need to get rid of roots.
Q. Does boiling water kill tree roots?
Not really. Boiling water can kill tender plant tissue that it directly contacts, but it is not an effective way to kill an established tree root system. Large roots underground are insulated by the surrounding soil and can resprout even if smaller exposed portions are damaged by hot water.
There is also a significant burn risk involved in carrying and pouring large quantities of boiling water outdoors.
Q. Does vinegar kill tree roots?
No, household vinegar is unlikely to kill an established tree or its root system. The acetic acid in vinegar works primarily as a contact herbicide, damaging plant tissue it touches rather than traveling through the plant to kill distant roots.
Stronger horticultural vinegar can cause much more severe plant damage, but it is also corrosive and can injure skin and eyes. For established tree roots, cutting, excavation, or professional removal is a more reliable approach.
Q. What kills tree roots?
Cutting off a root system’s access to energy will eventually cause the roots to die, which is why removing a tree and preventing stump sprouts is usually the most reliable approach. Concentrated salt can also damage roots by interfering with water uptake, but it can harm surrounding soil and plants as well. For roots that need to be removed immediately, cutting or excavation is generally more dependable than trying to kill them in place.
