Removing a mature walnut tree is a significant undertaking, often prompted by its immense size, aggressive root system, or the presence of juglone. Black walnut trees produce this allelopathic chemical, which acts as a natural herbicide released primarily from the roots, hulls, and leaves. This substance can suppress or kill many surrounding plants, making removal necessary for homeowners wishing to cultivate a diverse garden space. The process requires careful planning and a targeted approach to ensure the entire root system is neutralized and regrowth is prevented.
Necessary Preparations Before Tree Removal
Before any physical action begins, administrative and safety measures must be addressed to protect property and comply with local regulations. Homeowners must contact the national 811 “Call Before You Dig” service at least a few business days prior to any planned excavation. Utility lines, including gas, electric, and communication cables, are often buried just below the surface, and damaging them can result in serious injury or costly repairs.
Consult local municipal codes or Homeowners Association (HOA) rules, as many jurisdictions require a permit for removing large-diameter trees. Failing to obtain authorization can result in significant fines, especially if the tree is deemed a protected species. Proper safety gear, including hard hats, safety glasses, and sturdy work gloves, should be prepared to mitigate the risks associated with handling large wood and specialized cutting tools.
Mechanical Methods for Eradication
Mechanical removal involves physically cutting the tree down, but girdling can be used as an alternative method to kill the tree while it is still standing. Girdling interrupts the flow of carbohydrates from the canopy to the root system by removing a complete ring of the vascular cambium and phloem layer. This layer, located just beneath the bark, is responsible for transporting sugars, effectively starving the roots over time.
To perform a proper girdle, a sharp tool, such as a hatchet or chainsaw, is used to make a continuous cut all the way around the trunk, penetrating through the bark, cambium, and slightly into the sapwood. The cut band should be several inches wide to prevent the tree from bridging the wound with new growth. While girdling alone will eventually lead to death, it can take months or years and often encourages prolific sprouting from the base, necessitating chemical treatment.
Felling a large walnut tree, which is often dense and heavy, requires extreme caution and a clear understanding of directional cutting. The high risk of property damage or injury makes professional arborist services advisable for large trees. If the tree is felled, the remaining stump must be immediately treated with herbicide to prevent the vigorous regrowth, or suckering, common with walnuts. For trees that are too large or hazardous to fell, combining girdling with a targeted herbicide application is the most practical solution.
Targeted Herbicide Application Methods
For effective eradication, systemic herbicides must be applied directly to the living tissue of the standing tree so the chemical can be translocated down to the roots. The “hack and squirt” method involves making downward-angled cuts (or frills) around the trunk circumference with a hatchet or axe. Herbicide is then immediately squirted into each fresh cut, ensuring contact with the cambium layer.
A standard guideline is to make one cut for every one to three inches of trunk diameter at chest height, spacing the cuts evenly around the tree. Herbicides containing triclopyr ester, such as Garlon or Crossbow, are preferred because they are highly effective on woody species like walnut. They also carry a lower risk of “flashback” to desirable, root-grafted neighboring trees compared to glyphosate. The most effective time for this application is in late summer or early fall when the tree is actively moving nutrients downward to the roots for winter storage.
For smaller walnut saplings, especially those less than six inches in diameter, a basal bark application can be used instead of cutting. This involves spraying a solution of triclopyr ester, typically mixed at a 20 to 30 percent concentration in an oil-based carrier, onto the lower 12 to 15 inches of the trunk. The oil carrier helps the herbicide penetrate the bark and move into the cambium, and it is crucial to thoroughly wet the entire circumference of the base.
Preventing Regrowth and Eliminating the Stump
The remaining stump and root system pose the greatest threat of regrowth and continued juglone contamination, requiring immediate action. Once the tree is cut down, a concentrated herbicide must be applied to the fresh-cut surface within minutes to ensure absorption before the wood dries and seals. The chemical should be painted or sprayed directly onto the cambium layer, which appears as a light-colored ring just inside the bark, as this is the only living tissue that will transport the herbicide to the roots.
Failure to treat the fresh stump will result in multiple vigorous sprouts, known as suckers, emerging from the root collar and surrounding roots. Using a product with triclopyr or a high-concentration glyphosate is effective for this cut-stump treatment. Even with chemical treatment, the large stump may be mechanically removed through stump grinding, which pulverizes the wood and root crown several inches below the soil surface.
The allelopathic compound juglone will eventually dissipate once the root system is dead and begins to decay. While juglone is concentrated in the roots, the toxic effect in the soil typically degrades within a few months to six months after the tree’s complete removal. Tilling the area is not necessary and may even be counterproductive, as the soil can naturally cleanse itself as the dead root material breaks down.