new bed?

I'm having someone dig out a bed in my side yard, partially under a maple tree. Another bed about 2 feet from the edge of the new one is thriving. My plan is to replace much of the new bed (dry, rocky, rooty) with my old maple tree leaf pile from the other side of the house. Just wondered if this sounds reasonable. Thinking of some baby rhododendrons, bleeding heart, hellebore, creeping phlox. Old leaf pile is not quite sophisticated enough to be called compost pile, but I figure the bottom of it is probably pretty broken down. These and similar plants are doing well nearby. Suggestions?

If it were my leaf pile and my bed, I'd do it for sure. I'd definitely put some good quality top soil in there too, and a nice layer of mulch on top... Gretchen :)

Thanks, I've already had the bed dug and the leaf pile moved. I was thinking of topsoil to sort of weigh down and bind together. I think the leaves are fairly broken down, but they seem kind of fluffy. I want plants to have something a little firmer to dig into.