Tree girdling involves the deliberate removal of a complete ring of bark and the underlying cambium layer from a tree’s trunk. This technique is employed to kill or severely weaken a tree without the immediate labor and disruption of felling it. Girdling is a management tool used in forestry to thin stands, create wildlife snags, or eliminate invasive species. The process initiates a slow, physiological death that can take months or even years to fully complete by interrupting the tree’s internal transport system.
The Biological Reason Girdling Kills a Tree
The effectiveness of girdling is rooted in the specific structure of a tree’s vascular system. Trees utilize two separate tissues for transport: the xylem and the phloem. The xylem, which makes up the main wood of the trunk, moves water and dissolved minerals upward from the roots to the leaves. The phloem tissue, located just beneath the outer bark, transports sugars and carbohydrates created during photosynthesis down to the root system.
Girdling works by completely severing this phloem layer around the entire trunk. This interruption starves the roots of the energy they need to survive, as the sugars cannot travel past the cut. Since the inner xylem tissue is often left intact, the tree can continue to draw water and minerals upward. This temporary, one-way flow allows the upper canopy to remain green and appear healthy for an extended period until the stored carbohydrate reserves in the roots are completely depleted.
Essential Tools and Safety Preparation
Gathering the correct equipment and prioritizing safety is necessary before beginning the process. A hatchet or a specialized draw knife is typically needed for smaller trees, while a chainsaw is the most efficient option for larger trunks. A sharp chisel or a similar prying tool will also be necessary to remove the loosened bark and cambium.
Personal protective equipment is required, particularly if using a chainsaw. This gear includes:
- A hard hat
- Protective eyewear
- Sturdy gloves
- Steel-toed boots
Before starting any cuts, clear the area surrounding the tree of tripping hazards to ensure a safe working environment.
Detailed Steps for Girdling
The physical process of girdling begins with marking the desired area on the trunk, typically at a comfortable working height. The most common technique involves making two parallel, horizontal cuts, known as kerfs, completely encircling the tree. These cuts must be separated by a predetermined distance to create a wide enough gap for successful girdling.
Using a chainsaw or hatchet, the first cut is made completely through the outer bark and phloem layer, penetrating slightly into the xylem wood. Ensure the cut is continuous around the entire circumference, which can be challenging on trees with deeply furrowed bark. The second parallel cut is then made 4 to 8 inches above the first, also penetrating to the xylem.
Once the two horizontal cuts are finished, the bark and cambium layer between them must be completely removed. Use a chisel or specialized tool to pry and scrape away the entire ring of tissue, exposing the underlying bare wood of the xylem. No slivers of the inner, living cambium layer should remain, as this tissue is responsible for healing and could form a “bridge” across the gap, preventing the tree’s death.
Maximizing Effectiveness Based on Tree Species and Season
Girdling is most effective when performed in the late spring or early summer, just after the leaves have fully expanded. During this period, the tree has utilized a large portion of its stored root carbohydrates for new growth, making it physiologically vulnerable to the interruption of the phloem flow. This timing also correlates with the period when the cambium layer is actively growing and moist, often called “bark slipping,” which makes the removal of the bark strip significantly easier.
Attempting to girdle a tree in the late fall or winter is more challenging because the bark is tighter, and the root system has likely replenished its carbohydrate reserves for dormancy. Species-specific resistance is also a major factor, as certain hardwoods possess a strong ability to sprout from the roots or below the girdle.
Trees like maples, oaks, and the invasive tree-of-heaven are known for this vigorous re-sprouting ability, which can negate the girdling effect. For these difficult species, the addition of a potent herbicide applied directly to the exposed xylem surface immediately after girdling is often necessary to ensure root death.
The width of the removed ring also influences effectiveness by preventing the tree from healing itself. A gap of at least 4 to 6 inches is recommended to prevent the tree from forming callus tissue that could bridge the wound. A narrow gap risks allowing living tissue to grow across the exposed wood, reconnecting the phloem and allowing the downward flow of nutrients to resume.