Topping is an unfortunately common pruning practice that ignores a basic tenet of arboriculture: pruning back to a natural branch juncture. Failing to do so leads to the onset of watersprouts - many small branches that emerge from dormant buds in the area of the cut.
When a branch breaks in a storm, this new growth helps a tree to restore its canopy. When unnatural wounds that resemble branch breakage appear throughout the canopy, watersprouting happens at each of these cuts, and the tree is drained of energy from over-producing the sprouts. That makes the tree weaker and more susceptible to insect and disease problems. What's more, the sprouts create structural problems down the road. It is not uncommon for a topped tree to decline to the point of being unsalvageable.
I've taken some photos of topped ornamentals I've seen around town in Larchmont and Mamaroneck for you to see below.
--Jeff Delaune, Almstead Arborist in Lower Westchester County, NY.
|Topping to create a uniform, rounded shape is common on|
ornamental trees like Pears and Crabapples, but ultimately
this leads to a messy, structurally unsound canopy.
|Close-up of fresh topping cuts on a Crabapple|
|Close-up of an Elm that was topped a couple of years ago. Notice the|
thick water sprout growth that emerged after the improper
cuts were made.
|Here is a very clear example of water sprouts emerging from the |
sites of improper topping cuts. Good reduction cuts will scale
back the size of a tree while taking structure and growth
patterns into account.
Image: Joseph O'Brien, USDA Forest Service, Bugwood.org