06 Apr What is Topping and Why it Hurts Trees
What is Topping and Why it Hurts Trees
Topping is the indiscriminate cutting of tree branches to stubs or lateral branches that are not large enough to assume the terminal role. It is perhaps the most harmful tree pruning practice and is not an acceptable pruning technique. Topping often removes 50 – 100% of the leaf bearing crown. Because leaves are the food factories of a tree, removing them can temporarily starve the tree.
Homeowners sometimes feel that their trees have become too large for their property and fear that tall trees may pose a hazard. Topping is not a viable method of height reduction and will make a tree more hazardous in the long run.
The severity of the pruning triggers a kind of survival mechanism. The tree activates latent buds, forcing the rapid growth of multiple shoots below each cut. The tree needs to put out a new crop of leaves as soon as possible. It needs all of its leaves so that it can manufacture food for the trunk and roots. If the tree does not have the stored energy reserves to do so, it will be weakened and may die. The shoots develop from buds near the surface of the old branches. Unlike normal branches that develop in a socket of overlapping wood tissues, these new shoots are anchored only in the outermost layers of the parent branches. The new shoots grow quickly and are prone to breaking, especially during windy conditions. A regrown limb never has the structural integrity of the original. While the homeowners’ goal was to reduce the height of the tree to make it safer, it actually makes the tree more hazardous.
The pruning practices below are some possible alternatives to tree topping:
Crown Cleaning – the removal of dead, diseased, crossing or defective limbs to improve the health and structure of the tree.
Crown Thinning – crown cleaning with the additional removal of selected branches to increase light penetration and wind movement, and to decrease weight in the canopy.