6 Ways to Chemically Kill a Tree

Homeowners usually welcome trees on their property. But some trees are invasive species that, over time, can take over a garden. Other trees may overwhelm your home, digging roots into the foundation or limiting access to light.

Whatever the reason, if you're ready to kill a tree, you'll need to review your options and make an informed choice about the best method for your situation. If you're concerned about chemicals or are removing a tree in an area where you grow fruits or vegetables, you might choose to physically remove the tree. If you're comfortable using chemical herbicide, however, a number of options are available.

Chemical herbicides are effective and relatively low cost. On the other hand, they involve using potentially harmful substances in your own backyard. There are ways to mitigate the risk, but you might prefer to avoid chemicals altogether. In that case, you have two options for tree removal: cutting down or starving the tree.

Cutting Down a Tree

If you're removing a very large tree or are uncomfortable using a chainsaw, you can hire someone to take down your tree. Many people, however, simply cut down their own trees. Once the tree has been cut to a stump, you'll need to grind the stump to the ground.

Read More

5 Ways to Apply Tree Herbicide

By Steve Nix

Unfortunately, cutting and grinding might not be enough to kill your tree. In some cases, trees will continue to sprout from the stump. If this happens, you'll need to systematically look for new sprouts and cut them down whenever they appear. By cutting the sprouts, you deny the roots the energy they need to continue to grow.

If neither grinding the stump nor cutting sprouts is enough to kill your tree, you'll have to dig down and painstakingly remove the roots from the soil. The notorious buckthorn bush/tree is an example of a species that can be killed only by completely removing the roots.

Starving a Tree

The bark of a tree is a system for transporting soil nutrients and moisture to the branches and leaves. With some trees, fully removing the bark around the circumference of the tree's trunk will effectively starve it to death. This technique, called "girdling," often is effective, but it isn't foolproof. In some cases, trees can bypass or "jump" the girdle.

To get the best results, remove all layers of bark in a circle around the tree, cutting about 1.5 inches deep with a hatchet or ax. The girdle will need to be about 2 inches wide to kill a small tree and up to 8 inches wide for a large tree. 

Chemically Killing a Tree

Herbicides can kill trees and, properly applied, be safe for the environment. The most environmentally friendly options involve applying herbicide to a specific area of the tree. In some cases, however, the only viable option is to use herbicidal spray. There are five major types of herbicides, only some of which are rated for home or crop use. Triclopyr amine and triclopyr ester are growth regulator-type herbicides, while glyphosate and imazapyr kill plants by interfering with the synthesis of plant proteins. Aminopyralid is primarily effective on legumes such as kudzu and may not be appropriate for your needs. Here are six ways to chemically kill a tree:

• Cut Surface Treatments: This technique involves creating a pathway through the bark so that herbicide can be introduced into the plant's vascular tissue. Start by making a series of downward cuts around the circumference of the tree with an ax or hatchet, leaving the frill (cut section of bark) connected to the tree. Immediately apply the selected herbicide into the cuts. Avoid spring applications when sap flowing from the wound will prevent good absorption.
• Injection Treatments: Use specialized tree injection equipment to administer a specific amount of herbicide into the tree when the cut is made. Treatments are effective when injections are made every 2 to 6 inches around the tree. For best results, treat trees 1.5 inches or more in diameter at chest height. Injection is often handled by a tree removal company because it requires an investment in equipment.
• Stump Treatments: After cutting a tree down, you can minimize the possibility of regrowth by immediately treating the freshly cut surface with herbicide to prevent sprouting. On larger trees, treat only the outer 2 to 3 inches, including the cambium layer, of the stump (the internal heartwood of the tree is already dead). For trees 3 inches or less in diameter, treat the entire cut surface.
• Basal Bark Treatments: Apply herbicide to the lower 12 to 18 inches of the tree trunk (on the bark) from early spring to mid-fall. Some species can be treated during winter. Use herbicide spray mixed with oil until the bark is saturated. The low-volatile ester formulations are the only oil-soluble products registered for this use. This method is effective on trees of all sizes.
• Foliage Treatments: Foliar spraying is a common method of applying herbicides to brush up to 15 feet tall. Make applications from early summer to late September, depending on the choice of herbicide. Treatments are least effective during very hot weather and when trees are under severe water stress.
• Soil Treatments: Certain soil treatments applied evenly to the soil surface can move into the root zone of targeted plants after ample rainfall or overhead moisture. Banding (also called lacing or streaking) applies concentrated solution to the soil in a line or band spaced every 2 to 4 feet. You can use this type of application to kill large numbers of trees.

Important Tips

Before starting a tree removal project, learn how to use herbicides safely and legally. Herbicide treatments of roots or soil (or sprayed herbicides) can kill vegetation unintentionally.

• Call your local Cooperative Extension Service for detailed chemical information pertaining to chemical treatments. You're responsible for the chemicals you use and their ultimate effects.
• When using frilling or cut stump methods of treatment, apply the herbicide immediately so that your tree doesn't have a chance to start healing itself and you can achieve maximum absorption.
• Plant roots can share vascular tissue through root grafting, which occurs primarily within the same species but can occur between plants within the same genus. Your herbicide can move from a treated tree to an untreated tree, killing or injuring it.
• Once the herbicide is released from a tree, it can be available for uptake by another. The serious consequence is that a treated tree may release herbicide back into the environment, injuring nearby trees and vegetation.
• Adding stains or dyes to the herbicide solution substantially increases applicator accuracy. Applicators use the dyes to monitor treated trees, so they are less likely to miss or respray targeted trees. Use of stains can also indicate personal exposure.
• Avoid applying herbicide in areas where it can injure other plants. Assume that tree roots extend a distance equal to the height of a tree in dry climates and equal to half the tree height in wetter environments.