In the middle of a Chicago winter, yardwork of any kind is probably the last thing on your mind.  The ground in your yard is likely frozen and the plant life, including the grass, trees, and shrubs are dormant.  For the most part, you must wait until the spring to start your yardwork for the new growing season.  However, there is one thing you can do during the winter to help your trees and shrubs; pruning.  Tree pruning is highly recommended...