In some cases, a tree can regrow cut roots, and repair damage. However, the roots are the lifeline of a tree. If you cut them, you can damage, weaken, and possibly even kill your tree. If you cut essential support roots, the tree may even fall, where it can incur major property damage.
In order to keep your home and your tree safe, avoid cutting roots whenever possible. If necessary for excavation projects or installing irrigation systems, it’s okay to cut small roots. If large support roots are wreaking havoc on your driveway or foundation, it is often much safer to remove the tree, rather than attempt to cut invasive tree roots.
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Will Cutting Roots Hurt Your Tree?
Cutting any tree root does damage to the tree. Root structures perform two main functions for your tree. First, the roots serve as support that holds the tree upright. Second, the roots gather water and nutrients from the soil that keep the tree alive and growing. Root pruning risks compromising both these functions.
- Any damage to tree roots can harm your tree.
- Roots are responsible for holding the tree upright.
- Your tree absorbs water and nutrients from the soil through the roots.
Any root damage to a tree is potentially harmful, and cutting tree roots can have several negative effects.
What are the Dangers of Cutting Tree Roots?
If you cut one or more roots, you may cause the tree to weaken over time, become more susceptible to disease, or remove the support that keeps it upright. Cutting a tree’s roots can kill it, make it sick, or even cause it to fall.
- Diseased or sickly trees.
- Tree death (this may occur quickly or could take 2–3 years).
- Increased chance the tree will fall over.
If you cut off the oak roots that are currently growing under your driveway, you could create more problems than you solve. After all, the root is still under the driveway, making tree root removal impossible without tearing up concrete. In addition, you could kill that oak, leaving you with a dead tree in your yard. Even worse, without that supportive root, the oak could fall over in a windstorm and damage your house.
How to Safely Cut Tree Roots
If you must cut tree roots, there are ways to do so to mitigate tree damage and help ensure your tree bounces back. The things to keep in mind are:
- Avoid cutting roots close to the trunk. The further from the trunk you cut the root, the easier it is for the tree to recover.
- For trees over 15 feet (4.5 meters) tall, do not cut roots within 5 feet (1.5 meters) of the trunk.
- For trees under 15 feet tall, do not cut roots within 2 feet (60 cm) of the trunk
- With trees over 15 feet, never cut roots larger than 2 inches (5 cm) in diameter.
- With trees under 15 feet, never cut roots larger than a pencil’s thickness.
These rules will help protect your trees from unintended harm. However, backyard excavation projects may require you to dig irrigation lines that sever tree roots. As long as you follow the rules above and plan accordingly, you can complete your projects without harming your trees.
How to Repair Cut Tree Roots
If your tree’s roots have been damaged during construction, excavation, or a lawn care project such as rototilling soil, there are a few things you can do to encourage your tree to recover. These include:
- Provide plenty of water: Include your tree’s root zone in your lawn watering plan and keep the soil moist. A tree with root damage has a reduced ability to gather water from the soil, so it may need additional help.
- Spread mulch around the base of the tree: This will help maintain soil moisture, further helping the root systems pull in water and begin to repair the damage.
- Support the tree: If the tree is under 15 feet (4.5 meters) tall, use stakes and cables to support it if it has suffered root damage. This can help keep a damaged tree upright as it tries to repair its support roots.
Large trees are too massive to be easily supported with cables. If a large tree near your home has suffered damage to major roots, contact an arborist to assess whether the tree is in danger of falling and requires removal. If this is the case, you can then plan to remove the roots after the tree is gone.
Alternatives to Cutting Tree Roots
If you are considering cutting the roots of a tree but doing so would put the tree in danger of sickness, death, or falling, consider these options instead:
- Tree removal: If an excavation or building project (such as pool installation) would require cutting large tree roots, it may be better to remove the tree. This will prevent dangerous tree falls or tree disease and death.
- Transplant: If the tree is relatively small and the main root ball can be excavated, consider transplanting the tree to a safe location where its roots won’t interfere with structures.
- Acceptance: If a tree root is buckling a concrete sidewalk or driveway but isn’t damaging the structural foundations of your home, it’s best to leave the root alone. Similarly, exposed tree roots should not be cut for cosmetic purposes. If you don’t like the look of above-ground roots, consider spreading mulch beneath the tree.
Most cases of root infiltration fall into two categories: harmful and not harmful. If the root is damaging a foundation or sewer system, then it is harmful. The best course of action, in this case, is to remove the whole tree or attempt to kill it without cutting it down. If the tree is buckling a concrete walkway, then it isn’t harmful and is best left alone.
Can Tree Roots Grow Back After They are Cut?
In some cases, tree roots will grow back after they are cut. However, this is most likely in the case of small roots that are cut during the course of minimal excavation several feet from the tree trunk. Large tree roots cut close to the trunk can seriously weaken or kill the tree, and may cause it to fall. If your project demands you cut a supporting tree root, it’s usually best to consider removing or transplanting the entire tree.
If you damage tree roots during a lawn excavation or earth tilling project, provide the tree with plenty of water and mulch the soil near the tree, to help it retain moisture. This will aid the healing process. If the damaged tree is under 15 feet (4.5 meters) tall, support it with stakes and cables as it attempts to recover.