in regards to sirKris' roses:
was there a rose bush on the outer wall outside joining the two? if so, read below
so it sounds like the plant is being fed through the root systems of an outside plant, so it'll stay alive, but since it is concealed, it won't trigger chlorophyl production, keeping it white. it'd be cool to try this with a darlingtonia runner, I might imagine it would be a great contender for something like this, if ever i get runners this summer, i will definately try this technique to see if my theory is correct, just have to figure out how to avoid rotting and mold in a dark damp area.
i might be way off as well! just my 2¢