Unwanted woody vegetation, commonly referred to as brush, presents a significant challenge because its robust root system allows it to persistently regrow after being cut down. Mechanical removal alone provides only a temporary solution, as the viable root crown and lateral roots remain intact, ready to send up new shoots (resprouting). Achieving a permanent kill requires a systemic strategy. This involves introducing a chemical agent directly into the plant’s vascular system, ensuring the agent is translocated throughout the phloem and into the root system, ultimately killing the entire organism.
Preparing Woody Plants for Permanent Kill
The first step in effective brush control involves physically preparing the plant to accept the chemical treatment deeply and efficiently. Spraying the leaves of mature woody brush is often ineffective because the waxy cuticle on older foliage limits absorption. Instead, a targeted mechanical reduction is necessary to create a fresh, accessible wound that bypasses this protective barrier. This preparation involves cutting the brush close to the ground, creating a stump that acts as a direct port into the plant’s internal transport system.
For larger trees that are too difficult to cut down, a process called girdling or “hack-and-squirt” can be used to expose the inner wood and cambium layer. Timing the treatment is important to maximize the chemical’s movement to the roots. The most opportune time is typically late summer or fall when the plant is naturally moving sugars and starches downward into the roots for winter storage. This natural translocation process effectively pulls the applied systemic herbicide along the phloem pathway, ensuring it reaches the root crown for a complete kill.
Systemic Herbicides and Their Action
Permanent eradication relies exclusively on systemic herbicides, which are designed to move throughout the entire plant, unlike contact herbicides that only damage the tissue they touch. The two most effective active ingredients for woody brush control are concentrated glyphosate and triclopyr. These chemicals target specific biological processes within the plant, leading to a complete shutdown.
Glyphosate is a non-selective inhibitor that disrupts the shikimate pathway. Once absorbed, it is transported via the phloem to all metabolic sinks, including the root tips and meristems, effectively starving the plant of the proteins it needs to survive. Triclopyr is a selective, auxin-mimicking herbicide that targets broadleaf and woody species while sparing grasses. It acts like an overdose of natural plant growth hormones, causing uncontrolled, abnormal growth, which rapidly plugs the plant’s vascular tissues.
Triclopyr is available in two main formulations: an amine salt (water-soluble, used for foliar sprays) and an ester formulation (oil-soluble). The oil-soluble ester is significantly more effective for penetrating the thick, waxy bark of woody plants. For basal bark treatments, the ester formulation is mixed with a specialized basal oil carrier to enhance absorption directly through the bark. Both active ingredients require careful handling, as concentrated glyphosate is non-selective, and triclopyr can volatilize and drift, posing a risk to desirable broadleaf plants nearby.
Precision Application Methods
The success of a systemic herbicide depends entirely on precision application, ensuring the chemical enters the living tissues of the plant. The Cut Stump Method is highly effective and involves applying the chemical to the fresh, open wound of a recently severed stem. After cutting the brush horizontally near the soil line, the herbicide must be applied immediately to the stump’s cambium layer, the thin, light-colored ring just beneath the bark.
Immediate application is necessary because woody plants rapidly form a protective callus over the cut surface, often within minutes. For stumps larger than three inches in diameter, only the outer ring of living tissue needs to be treated, as the center heartwood is dead and cannot transport the herbicide. The appropriate systemic concentrate (often a 50% solution of concentrated glyphosate or high-concentration triclopyr) can be applied using a paintbrush, squirt bottle, or low-volume sprayer to saturate the cambium layer without excessive runoff.
An alternative technique, the Basal Bark Method, is ideal for smaller brush and saplings with smooth bark, typically those under six inches in diameter. This method involves applying the oil-soluble ester formulation of triclopyr mixed with a basal oil carrier directly to the bark of the standing plant. The mixture must thoroughly wet the entire circumference of the lower 12 to 18 inches of the trunk, soaking the bark down to the root collar at the soil line. The oil carrier allows the herbicide to penetrate the intact bark and move into the phloem, resulting in a complete kill without the need for cutting first.
Ensuring Long-Term Eradication
Achieving a permanent solution requires diligent follow-up and management of the treated area after the initial application. Even with successful treatment, the root system may produce new shoots, or suckers, from missed root fragments or the root collar. Monitoring the site for several months and spot-treating any new growth is necessary to fully exhaust the remaining energy reserves in the root system.
Emerging suckers or sprouts can be treated with a foliar application of a systemic herbicide or by applying the cut-stump method to the small new stems. When applying herbicide, avoid overspray or runoff to protect surrounding desirable vegetation, as root systems can sometimes graft together. Once the brush is eliminated, revegetating the cleared area with desirable groundcover, such as native grasses or shrubs, is beneficial. This step helps stabilize the soil and prevents the newly open ground from being rapidly colonized by opportunistic or invasive species.