I did a cake that had vines of gumpaste flowers on the bottom two tiers. They were combinations of orchids and freesia-type flowers on a stem.
To get this effect I used to dummies to make the vines. I put a skewer in the center and attached a wire to the skewer so that I could see how long the vines had to be to make it from the top to the bottom of the tiers. I hooked the flowers onto the wires and did enough to cover the whole cake the way that I wanted it.
I then removed the vines from the dummies, and pinched the stems with pliers to flatten out the wrapped flower stems.
After that I wrapped the stems with floral tape to make sure that nothing would move.
When I set up the cake at the reception site I put a skewer in the center, hung the vines on it, then put a flower on top of that to cover it up. I filled in any empty spaces with more gumpaste, and there you have it!