Regional Gardening Reports :: National Gardening Association

In the Garden:
Southwestern Deserts
May, 2010
Regional Report

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After topping trees resprout with numerous weak shoots, creating a top-heavy tree prone to tip during strong winds.

Why Tree Topping Doesn't Work

Tree topping- indiscriminately cutting back a tree's crown, leaving behind ugly stubs- has been discredited by researchers and arborists for years. Unfortunately, some trees still suffer from this misguided practice because owners or landscapers think it is the only way to reduce a tree's size. In reality, topping is a temporary action that creates its own set of problems.

Topping Doesn't Reduce Tree Size
When a large amount of foliage is removed during topping, a tree's photosynthesizing capability is suddenly reduced, basically "starving" the tree. It jumps into survival mode to replace the missing foliage by sprouting multiple shoots below each pruning cut. These sprouts grow very rapidly, as much as 10 or 20 feet in one year, depending on species. Ironically, a topped tree can quickly regain its original height, defeating the pruner's initial goal of size reduction.

Topping Creates a Hazard
Although fast growing, these new sprouts are weakly attached because they arise from buds just below the bark surface. Normal branches are more deeply anchored within the wood tissues to support their weight. As the regrowth gets heavier, it's prone to crack and break, creating a dangerous situation. Also, a sudden top-heavy flush of growth creates a tree susceptible to blowing over in windstorms.

Topping Promotes Decay and Death
Fueling this sudden need for replacement foliage weakens and stresses the tree. Stressed plants are more vulnerable to attack by pests. Coincidentally, those many open pruning wounds created by topping provide easy entry for insects, diseases and rot-causing organisms. Branches and trunk areas that were previously shaded by foliage are now exposed to the sun's rays. Sunburned tissue cracks and splits, creating more opportunities for pests.

Topping Reduces the Many Benefits of Landscape Trees
Topping destroys a tree's natural branching structure and eliminates the shade it could provide. Expansive shade canopies lower temperatures around the home, reduce utility costs, absorb air pollutants and act as windbreaks. Initial topping is costly. Once topped, a tree requires regular maintenance to deal with the above described problems. So, what to do if your tree is too tall? Healthy, well-maintained trees increase property values so it makes sense to treat them as long-term investments. Consult a certified arborist to advise you on the best course of action, which may include selectively pruning branches to reduce a tree's size in a process called "crown reduction" or "drop crotching." In some cases, such as beneath utility wires, it may make more sense to remove the tree and replace it with a shorter species.

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