Tree topping

Tree topping is the practice of removing whole tops of trees or large branches and/or trunks from the tops of trees, leaving stubs or lateral branches that are too small to assume the role of a terminal leader. Other common names for the practice include hat-racking, heading, rounding over, and tipping. Some species of trees are more likely to recover from the effects of topping than are others. There are alternatives to topping that can help to achieve the same goals without damaging trees.

Hundreds of large trees are topped each year, which causes significant stress and future safety issues. It has been shown through survey that the average person's knowledge on tree care is limited.

Another popular misconception is that a topped tree will benefit from increased light penetration. The removal of a large portion of a trees canopy can have detrimental effects. When a tree is topped, newly formed bark may be susceptible to sun scald. Prolonged exposure can severely damage the bark, thus creating an attractive home for decay causing organisms. Evidence of decay may be the presence of conks (fungal fruiting structures) on the outer tree bark. The loss of leaves reduces a tree's ability to photosynthesize and produce food. If a large tree is unable to produce enough sugars to feed the roots, it will slowly die from starvation.

Some people have been known to top trees in order to stimulate new growth. When a tree is topped, many adventitious shoots, known as suckers begin to grow from the wound. This is the tree's response to the sudden loss of leaves. Although the tree is able to produce an abundance of suckers, they are susceptible to numerous problems. Firstly, this adventitious growth is succulent and susceptible to attacks by insects such as aphids and caterpillars, and pathogens like fire blight (Rosaceae). Secondly, the branch-stubs that the suckers emerge from are rarely able to form a complete callus. This means that any pathogen that attacks a sucker may enter the tree directly though the open wound. If wood begins to rot it could create a weak branch connection between the developing suckers and the main tree leading to a possible branch failure. If a tree is unable to compartmentalize the fungi, it may reach the trunk and ultimately kill the tree.

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