root over rock?

I have a few plants that I would like to plant over a rock when I repot them. They are all deciduous, if that makes much of a difference. A Maple, Cherry, and Forsythia. I have read many ways of doing this. Some use peat muck on the rock, some just horticultural sand. Some use raffia some use plastic wrap. I am sure all of these methods accomplish the same results, however what have you found best in your experience. Does peat muck work better with some plants and not others? Will plastic wrap keep the roots too moist, and if so is there a way to alleviate this? Any advice will help. thanks.

I've used rubber bands wrapped tight around roots and rock. The rubber rots away in a season, but with roots and rock buried deep in a pot, the roots stay in contact with the rock until repotting in 2-3 years' time.

Jim,
Excellent use of the rubberband. I will use this method as well. I have always ran wire through aquarium tubing in the past.
Thanks for the inovative idea.
Abe