Decorate cake. Prepare three decorating bags with tip 3. Fill separately with light green, dark green and red icing.
Using light green icing, pipe horizontal line following mark on cake.
Using dark green icing, pipe needles along horizontal line. Repeat with remaining light green icing.
Using red icing, pipe berries along garland.
Prepare decorating bag with tip 1 and remaining white icing. Pipe vertical lines around cake, starting at bottom of garland and varying in length.
Attach various dot matrix icing decorations to bottom of each vertical line.