Elm trees are notorious for their aggressive and prolific root systems, often extending far beyond the canopy in search of moisture and nutrients. This extensive network can become problematic for homeowners, as the roots infiltrate small cracks in foundations, lift sidewalks and driveways, and seek out water sources in drain pipes and sewer lines. Eliminating the entire root system after the tree is felled is often the only way to prevent future structural damage and the persistent problem of root suckers. Methods range from mechanical removal to the strategic use of targeted chemical agents.
Killing Roots Through Physical Removal
Physical removal relies on mechanical force to eliminate the stump and a portion of the root mass, often preferred when chemical use is a concern. The most common technique for large stumps is professional stump grinding, where a machine reduces the stump into wood chips several inches below ground level, typically 6 to 8 inches. This process addresses the visible portion of the tree, allowing for immediate aesthetic improvement and preparing the area for new planting.
For smaller stumps or in areas where heavy machinery cannot access, complete excavation or hand-digging can be employed. Excavation involves digging out the entire stump and its largest roots, ensuring complete removal of the root crown. While highly effective, this process is significantly more labor-intensive and creates a large, disruptive hole requiring extensive backfilling and site restoration. The limitation of both grinding and excavation is that they often leave deep, lateral roots intact, which can still produce new shoots, known as suckers.
Using Targeted Chemical Agents for Root Elimination
Chemical treatment is a highly effective way to kill the entire root system using systemic herbicides that travel through the tree’s vascular system to the root tips. This approach is particularly effective at eliminating the extensive underground network that mechanical methods often miss. The most effective systemic agents are concentrated formulations of glyphosate or triclopyr, designed specifically for stump and cut-surface treatments. These chemicals must be applied to the freshly cut stump, ideally within five to fifteen minutes of felling, to ensure maximum absorption before the wound surface begins to dry and seal.
The proper application technique involves exposing the cambium layer, the ring of living tissue just beneath the bark, where the chemical is absorbed and transported. For a large stump, this is accomplished by drilling a series of downward-angled holes around the circumference or by making frill cuts—slightly overlapping downward slashes with a hatchet—into the cambium. The concentrated herbicide is then painted or squirted directly into these holes or cuts, thoroughly wetting the cambium layer without causing runoff. Applying the chemical to the outer two inches of the cut surface, which contains the cambium, is far more important than saturating the non-living heartwood at the center.
Safety is a serious consideration when using concentrated herbicides, requiring the use of personal protective equipment (PPE) such as gloves and eye protection. Care must be taken to prevent the chemical from contacting desirable surrounding plants, as systemic herbicides can be absorbed by the roots of nearby vegetation. The concentration of the herbicide is also important; while product labels may suggest high concentrations, a 20% glyphosate solution has been shown to be effective in preventing resprouts.
Long-Term Management and Preventing Suckers
Even after a successful chemical application to the main stump, elm trees possess a strong ability to regenerate from latent root buds, resulting in the appearance of suckers. These sprouts are a clear indication that the root system still holds energy and requires ongoing attention. Long-term management begins by monitoring the surrounding area for new shoots, as they can emerge from the lateral roots a considerable distance away from the original trunk.
Immediate removal of suckers is necessary, but simply mowing or cutting them often stimulates the root system to produce even more sprouts in response to the stress. For small, soft shoots, physically tearing or ripping them away from the root is a more effective technique than cutting, as this action can discourage re-sprouting. If the suckers are larger or persistent, a targeted spot treatment can be used by applying a low-concentration systemic herbicide directly to the cut surface of the new shoot.
Another preventative measure is to starve the remaining root fragments of light and energy through solarization or smothering. Covering the area with a thick layer of mulch or an opaque plastic sheet blocks sunlight and prevents any new sprouts from photosynthesizing. This practice, combined with vigilant monitoring and prompt, targeted removal of new growth, ensures the remaining root system is depleted of its stored reserves over time.