I have never made fondant flowers before.  I am making a cake for my grandma's birthday tomorrow and was originally going to just decorate with buttercream.  I saw a picture of a cake online that had a couple fondant flowers on it that I would like to do as some additional decorations for the cake.  I have ready to use fondant at home but no gum paste and no time to go to the store.  Is the gum paste absolutely necessary for the flowers to hold their shape?

It helps, but you can add some corn starch to it to make it stiffer if you don't have any tylose on hand.