So,... http://graphics.uni-konstanz.de/~luft/ivy_generator/
It is a very nice addition to the 3D toolkit.
This application actually grows an Ivy plant on a obj mesh.
(Beware: resulting meshes can be very LARGE; but by careful adjustment of certain parameters, this can be controlled.)
{I had to invert one of the transmaps; but it was a simple thing to do.)
Here's a quick example:
