Serves about 16.
In advance, on waxed paper covered cake circle, arrange pretzel rods in trellis shape, attaching rods to each other with green royal icing. Allow to dry completely. Add tip 5 vines and tip 352 leaves; let set.
On waxed paper covered cake circle make tip 12 orange royal icing carrots by piping a bead with heavy pressure; decrease pressure as you move tip, bringing end to a thin point. Add tip 352 green carrot leaf tops. Let set.
Bake Vegetable Patch Chocolate Cake in 13 x 9 in. baking pan following recipe directions. Cool cake in pan 10 minutes. Remove from pan and cool completely. Position cake on foil-covered cake board.
Spatula ice cake with medium tinted green buttercream. Add tip 21 dark green buttercream rope bottom and top border. Insert pretzel trellis into cake. Sprinkle crumbs over cake top. Arrange marzipan vegetables and carrots.