Maybe use the bezier draw tool to draw the vines, then animate the start and end positions like we did for the moving arrows thing a while back. If there is already some art of your vines available, use the bezier tools to trace over the originals and use it as an animated revealing mask?
You can draw a white line over one of your leafs and add a Write on Behavior to that line. Then add a image mask to the white line and it will reveal the image (leaf) below. It works awesome. And for my shameless plug. My Apple Motion training DVD thoroughly covers this and much more. Best of luck.