Attach pretzel rod inside sugar cone with royal icing. Pipe icing inside of cone and press pretzel into position. You could place the cone, point side down, in a glass to hold until icing is set, about 1 hour. The icing won't be completely dry, so handle carefully when you start to decorate the tree.
Using Tip 75 with the wide, flat point of tip up with green icing, pipe a row of leaves, starting at the base of the cone. Hold the pretzel rod in your opposite hand and turn slowly as you pipe the leaves.
Carefully loosen waxed paper from former and lift off icing tree. Remove paper; pipe icing inside tree to secure pretzel rod, let dry completely. Ice Cream Cones may be substituted for the tree former.
You could also make the trees completely on a waxed paper covered board, allowing them to dry and then attach them to the pretzel rods as needed.