This week, we are picking back up with our series on the native trees of Chicagoland.  We have so far covered the oak tree, dogwood, ash tree, and sassafras, and in this installment, we will cover the willow tree.  Willow trees are among the most recognizable trees in the Chicago area with their long, drooping branches and distinct catkin flowers.  There are over 400 species of willow trees, most of which are found in North America.  This...