I was wondering if anyone has ever heard of whipping a tree to make it grow? What is this practice called and how does it work?
I found this by doing a search. I have no experience with this. Is this what you are referring too?
The hardest cut of all seems to be the one needed right after planting, called "whipping" the tree. This procedure is done on newly planted, bare-root apple trees (usually with 1/2 - 5/8 inch trunk diameter) with only a few limbs. All limbs are completely removed and the main trunk is "whipped" down to 30-45 inch height. This will accomplish two things. It reduces the leaf area available the first year to match the minimal roots available and gives the new tree a good chance to establish the root system with minimal stress. It also encourages new and better branch development. If there are some very good branches on the tree when you plant it, these may be kept (if you just can't bring yourself to cut them). It is not advisable to "whip" larger, potted or ball-and-burlap apple trees.
Local nurseries used to take bare root trees and lop them off knee height to promote better branch development, but any drastic pruning of the young tree will delay bearing.
Bare root trees usually have the roots devastated upon harvesting and need branches removed in order to balance out the tree, which delays bearing also.
My advice is to plant tiny benchgrafts (infant trees) and train it up right using clothespins to promote good branch angles and minimal pruning. It will often start bearing earlier than buying a bare root tree the same time, and be a better tree over its lifetime.
Here is a more literal answer to your question:
"Is there any truth to the notion that whacking an unfruitful tree will stimulate it to produce? If so, how would that work?"
Answer here: http://lee.ifas.ufl.edu/horticulturearc ... ultree.htm