What is the effect of topping a 50 foot Norfolk Pine to stop its growth? Can the tree be thinned to reduce its vulnerability to wind damage?
Same as with topping other trees to stop growth and reduce wind vulnerability, it is a falsehood that damages the tree and actually makes it less structurally sound. Topped trees are deformed by the topping, do not stop growing unless so damaged they decline and lose enough vigor to grow, eventually die. Replacement tops grow off the side of the original stem(s), may pull off later when heavy enough.
In other words, don't. ;-) Norfolks are your usual kind of tree to begin with. If it's that much of a problem, take it out all together, or deal with it as-is.
I agree with the two replys before me. It is better to remove the tree and re-plant with a more suitable species to the local enviroment. Removing the tops of trees results in a multi stemming effect with very poor branch attachment and they can breakaway from the tree and fall. Here in Sydney we have many Norfolk pines (Araucaria heterophylla) around the local landscape, some of which have been damaged in this way and they look quite hidious. Good luck with it. Ern (Arborist)
