soonami

There's been a lot written about the types of materials to make the muck for root over root plantings, but I think anything that has high water retention, such as clay or loam is very necessary. The organic materials like shredded leaves, peat, sphagnum moss, etc just help provide some structure. I don't know of any reason why you can't use maple leaves if those are availible to you. Koreshoff recommends a part silt clay and 1 part fresh cow manure, John Naka recommends 1 part clay and a little more than 1 part shredded moss.

However, I would not recommend you use potter's clay, that kind of clay has a lot of silica and minerals that might be in too high of a concentration so as to dry out your tree. I would suggest that you use clay from your garden, like the clay that is underneath the foot or so layer of humus and top soil.

Good luck