Homeowners often consider tree topping—the indiscriminate removal of a tree’s upper canopy—to control the size of a rapidly growing tree or address clearance issues. However, professional arborists universally discourage this technique because it causes severe, long-term damage to the tree’s health and structure. Understanding why this method is detrimental is the first step toward adopting responsible tree care practices that work with a tree’s natural growth.
Defining Tree Topping and Its Appearance
Tree topping is the practice of cutting main vertical stems, or leaders, and large branches back to stubs. The cuts are made without regard for the location of lateral buds or the health of the remaining branch structure. It is also commonly referred to as “hat-racking” or “rounding over” due to the disfigured appearance it creates.
The immediate result is a tree with a flat, unnatural crown and large, blunt wounds. Unlike the precise, targeted cuts of proper arboriculture, topping leaves behind stubby branches that the tree cannot effectively seal off. This removes a significant portion of the tree’s crown, stripping it of its natural shape.
Biological and Structural Damage Caused by Topping
The severe nature of topping immediately puts the tree into a state of shock and stress. This practice removes between 50% to 100% of the tree’s leaf-bearing crown in a single session. Since leaves are the site of photosynthesis—the process by which a tree creates energy—topping effectively starves the tree.
To combat this sudden energy deficit, the tree activates dormant buds below the cuts. This produces a rapid flush of numerous, vertical, fast-growing shoots known as water sprouts or epicormic growth. While these sprouts quickly restore foliage for photosynthesis, they are structurally unsound because they lack the strong, overlapping wood tissues that form a proper branch collar. As they grow, they create a dense, bushy crown prone to breaking off in high winds or under snow load, making the topped tree more hazardous than before.
The large, indiscriminate cuts made during topping also expose the tree to decay organisms, insects, and disease. Trees manage injury through a process called Compartmentalization of Decay in Trees (CODIT), forming chemical and physical barriers to wall off the damaged area. However, the size of topping wounds often exceeds the tree’s capacity to compartmentalize effectively. Decay can then move freely into the main trunk, compromising the tree’s structural integrity and potentially leading to premature death.
Proven Alternatives for Reducing Tree Height
Arboriculturally sound methods exist to reduce a tree’s size and manage its structure while maintaining its health and natural form. The best approach is to avoid the need for drastic measures by selecting the right tree for the space at the time of planting. If a tree has grown too large for its location, a certified arborist can assess the situation.
Reduction Cuts
The preferred technique for managing height is a reduction cut, which is a precise pruning method. This involves cutting a dominant leader or branch back to a healthy lateral branch that is large enough to assume the terminal role. For a proper reduction cut, the remaining lateral branch should be at least one-third, and preferably one-half, the diameter of the limb being removed. This size ratio ensures the lateral branch is capable of sustaining the flow of nutrients and maintaining growth dominance. The cut redirects growth to a lower, smaller branch, effectively reducing the tree’s height while preserving its natural crown shape.
Crown Thinning
Another technique is crown thinning, which involves the selective removal of small, interior branches throughout the canopy. This method reduces the overall density of the crown, which improves air circulation and light penetration without significantly altering the tree’s height or shape. Thinned canopies also offer less resistance to wind, which helps prevent storm damage.
Structural Pruning and Removal
If a tree has grown too large for its location, a certified arborist can assess whether a gradual series of reduction cuts is feasible or if structural pruning can improve its architecture. If the tree is simply too large for the site, removal and replacement with a more appropriately sized species is often the safest long-term solution.