Why pruning a tree does not work, and may kill the tree
I always wondered why "pruning" or lopping the tops off of a tree never worked - Tree Torture by Valerie Easton explains why.
What stands in the way of (Cass) Turnbull's (pruner extraordinaire and founder of Seattle-based PlantAmnesty) aim to save Seattle's tree canopy? She believes the main problem is the continued belief that size can be dictated by pruning. Trees are genetically programmed to grow to a certain size, and pruning doesn't deter that. Tree topping has even been called vandalism for profit, because it not only ruins a tree's looks, but can kill it. Turnbull explains it this way: "People think they're cutting hair when they prune their trees, but it's more like cutting off your hands and feet. You're cutting into a vital body part of the plant, and it introduces decay." If your hair really did grow like a tree, every time you cut it, it would grow back out, twice as bushy, in just a couple of days.
So how can you deal with oversized trees? There's no good way to keep a tree short, says Turnbull. "Exercise your control over trees when you select them, not later when they've grown too large."
Good, informative article with helpful links for selecting the right trees for your property.