The Box Elder tree, Acer negundo, is a common North American maple species known for its rapid growth and adaptability to various soil conditions. Despite its hardiness, it is often viewed as an undesirable landscape tree due to its soft, brittle wood, which is highly prone to storm damage and breakage. Furthermore, the tree aggressively self-seeds, and female trees attract Box Elder bugs. Because of its tendency to quickly colonize cultivated areas, permanent removal is often necessary, requiring specific techniques to eliminate the robust root system.
Preparing for Removal and Timing
The timing of any removal strategy significantly affects its success, particularly when using systemic herbicides. The tree is most susceptible to chemical treatment during the late summer or early fall, which corresponds to the period of nutrient storage. During this time, the tree is actively transporting carbohydrates downward to the roots for storage over the winter. Applying a systemic herbicide during this downward flow maximizes the amount of chemical delivered to the entire root system, ensuring complete elimination and preventing aggressive re-sprouting.
Before beginning, always secure personal protective equipment (PPE), such as gloves, eye protection, and long sleeves, and read the herbicide product label for application instructions. Systemic herbicides are non-selective. To protect surrounding vegetation, avoid spraying on windy days and consider using a physical barrier, like a piece of cardboard or plastic, to shield nearby plants from accidental contact.
Systemic Chemical Elimination Techniques
Systemic chemical methods target and kill the living root system, which is the source of vigorous re-sprouting. The most common and effective systemic herbicides for woody plants like Box Elder contain active ingredients such as glyphosate, triclopyr, or imazapyr. The chemical must be applied directly to the growth-producing cambium layer.
The Cut-Stump Treatment is applied immediately after felling the tree. The herbicide must be painted or sprayed onto the freshly cut surface, specifically targeting the narrow, outer ring of living tissue within minutes of the cut. This immediate application is necessary because the tree quickly begins to seal the wound, which inhibits chemical absorption.
An alternative method is the Hack-and-Squirt or Frill Cut technique. This involves using an axe or hatchet to make a series of downward-sloping cuts completely through the bark and cambium layer. These cuts create small pockets into which the concentrated herbicide is immediately squirted or poured. The chemical is then absorbed directly into the vascular system, translocating to the roots.
Girdling and Mechanical Removal Alternatives
Girdling is a slow but effective method for killing a Box Elder tree in place. Girdling involves removing a complete band of bark and the underlying cambium layer. The removal of this layer interrupts the flow of photosynthesized sugars from the leaves down to the roots, effectively starving the entire root system.
The removed strip must be wide enough, typically 6 to 8 inches, to prevent the tree from healing over the wound. This method can take a year or more for the tree to fully die, allowing it to decay slowly. Mechanical Removal—cutting the tree down—is the fastest method, but it presents a challenge because Box Elder roots are highly prone to aggressive re-sprouting.
To prevent this vigorous regrowth from a remaining stump, the stump can be completely excavated or ground down several inches below the soil line. If grinding is not an option, the stump can be covered with a thick piece of black plastic or a heavy layer of mulch, which blocks sunlight and depletes the roots’ stored energy over time. Any new suckers that emerge from the roots must be promptly cut or mowed down to persistently exhaust the energy reserves in the stump.