It’s essential to kill tree roots after you cut down a tree. If you don’t ensure the roots are dead, they can continue to grow. This can cause the tree to regrow from the stump, and invasive roots can continue to destroy your foundation or septic system. The best ways to kill tree roots permanently are:
- Use a stump killer after felling a tree.
- Inject the roots or stump with concentrated Roundup.
- Flush copper sulfate, Dichlobenil, or salt solutions to kill roots in pipes and septic systems.
- Safely burn the stump to kill roots.
- Pull out the stump and roots.
Each of these methods is proven to work and will get the results you need. Tree stumps and roots will be dealt with quickly and easily.
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7 Ways to Kill Tree Roots After Cutting Down a Tree
When killing tree roots of a felled tree, it’s important to choose the right method for the situation. If you’re not concerned with removing the stump immediately, stump killer herbicides are the easiest way to kill trees to the root. If the tree you’ve cut down has sent invasive roots through the soil and into septic systems or sewer lines, you’ll need to take measures to kill them and start the decomposition process.
Use Stump Killer
The fastest and easiest way to kill trees down to the root is by using this stump killer. One application of a strong stump killer is usually all you need. Here’s how to use it:
- Apply stump killer to a fresh-cut tree. If it has been longer than 15 minutes since the tree was cut down, cut away the top inch of the stump to reveal fresh wood.
- Paint stump killer in 1-inch (2.5 cm) wide wing around the edge of the exposed wood.
- Allow 7–14 days for results.
- If the tree sends up new shoots following the application, repeat the previous steps for a second application.
A strong stump killer is a low-hassle way to kill tree roots quickly. To save yourself work re-cutting a stump, apply stump killer herbicides as soon as you fell the tree.
Inject Roots with Glyphosate
A concentrated weed killer with at least 50% Glyphosate, such as this product, can be used as an effective stump and root killer. This saves you the trouble of buying any specialized products. To use Roundup concentrate to kill trees:
- Use a drill and 1/2 inch (12 mm) bit to drill holes in the stump or tree roots.
- The holes should be 1–2 inches deep (2.5–5 cm).
- Space the holes in a ring around the top of a freshly cut stump, every 2 inches (5cm). Or drill them along exposed tree roots, every 2 inches.
- Use a spray applicator or squeeze bottle to fill the holes with concentrated Glyphosate weed killer at full strength.
- Allow 7–14 days for tree roots to die.
The Glyphosate in Roundup will penetrate root systems and kill the tree entirely. Although you may think of Roundup as a weed and grass killer, an undiluted concentrate with at least 50% Glyphosate has the capability to kill unwanted tree roots.
Flush Copper Sulfate
Invasive tree roots in sewer lines and septic systems are a problem that should be dealt with immediately to save yourself from a huge plumbing bill. Copper sulfate products are a great way to kill tree roots that have invaded your water lines. Here’s how to use it:
- Pour the recommended amount of this copper sulfate root killer into a ground-floor toilet.
- Flush to bring the copper sulfate into the pipes.
- Do not flush again for 8–12 hours, if possible. This gives the copper sulfate time to work through the pipes and attack invasive roots.
This solution is simple and will wipe out roots that clog and destroy pipes. However, it’s not the only option for killing invasive underground roots.
Use Dichlobenil Root Killer
This foaming root killer contains Dichlobenil, a herbicide that attacks tree roots. It can be applied in the same manner as copper sulfate products, but should be done so with care. Dichlobenil products foam on contact with water, so be prepared to flush quickly to prevent overflowing your toilet with foam.
- Can be used in the same manner as copper sulfate.
- Because of its foaming action is well suited for application in cleanout pipes.
If your septic system has a cleanout pipe (usually an outdoor pipe between the septic tank and your house) then pouring a Dichlobenil solution directly into the cleanout pipe is the best way to attack invasive roots in your septic tank.
Natural Root Killer with Salt
If you want to avoid chemicals when attacking the roots that have invaded your plumbing and sewer lines, you can mix a flushable root killer by following these steps:
- Mix 1 cup each of the following ingredients: salt, baking soda, and boiling water.
- Pour this mixture immediately into a ground-floor toilet and flush.
- Do not flush for 8–12 hours.
- Repeat this application once per week for 4–6 weeks.
This course of action is not as powerful as chemical root killers, so it may take several applications to kill roots and begin the natural decomposition process that will unclog your pipes.
Burn the Stump
You can get rid of a stump and kill the roots at the same time by burning the stump in place. This destroys the stump and pulls nutrients out of the roots as it burns, killing the roots still in the soil. Here’s how to safely burn a stump:
- Clear the area of flammable debris.
- For safety, use a hose to soak grass, plants, and soil in a 30-foot circle around the stump.
- Light the stump carefully, using firewood piled against the stump rather than relying on fuel or accelerants.
- Keep a fire extinguisher on hand.
- Do not leave the stump unattended while it burns—turn the event into a bonfire.
Keep in mind, fire is hazardous and this method shouldn’t be used if the stump is within 10 feet of your home, trees, and other structures. Also, if conditions are dry, there has been a recent drought, or winds are high, do not attempt to burn the stump. Check with your local municipality regarding the legality of outdoor fires before burning.
Pull Out the Stump
The simplest way to kill roots is to just pull them out of the ground. If the main stump structure and support roots have been removed, the remaining thin roots have an extremely low survival rate. Although this can be difficult with large trees, it’s often the best way to kill tree roots and remove an unsightly stump from your yard.
- Dig around the base of the stump. Cut exposed roots with a root saw or loppers.
- Once you have removed dirt down to a depth of 18–24 inches (45–60 cm), attach a winch or strap to the stump.
- Attach the other end of the winch/strap to a suitable truck, tractor, or other vehicle.
- Pull the stump out of the ground carefully.
- If desired, paint cut root ends with stump killer to ensure they die.
The best method for tree stump removal using a vehicle is by going in forward and reverse in short stretches. Do not simply go forward and increase the strain on the stump. This can result in stumps tearing loose violently, which can be dangerous for the vehicle and operator.
How Do You Kill Tree Roots After the Tree is Cut Down?
Once you’ve cut down a tree, you can kill the roots by applying a stump killer, or by using a concentrated Glyphosate-based weed killer as a tree-killer injection. To kill roots that have grown into underground sewer lines, flush the system with copper sulfate, Dichlobenil, or a salt/baking soda/water mixture. Finally, to remove the stump and kill the roots, either burn the stump or tear out the stump and roots together.
