Hi,valleylynn,
I can't dig into the top of the slope until the pigmy palm tree roots rot (25yrs of roots) - will take a couple of years to rot. (too difficult by hand - the last pigmy palm root ball taken out was 24 -36 inches height and width not counting the deeper roots and I hired someone to remove it a couple of months ago.). The clay soil won't wash away with the rocks on top of it, my concern was the potting soil. The clay soil underneath the rocks is thick heavy clay that doesn't drain quickly and from what I read sedum needs quick draining soil. That why I thought I use potting soil until I read you can plant sedum in rocks.
I can dig into the slope on the lower end and put flower bed soil mixed with potting soil, compost,pea gravel, plant the sedum in it and then add more pea gravel, then rock pebbles all around. The rocks should contain the soil underneath the sedum with a 2 inch bed of gravel and then I add some larger rocks for the sedum to grow over.
Eventually I want the rock garden to appear similar to this picture over time - adding different color shaped rocks and other small height plants. Though my garden section is larger than that picture - gives the idea though.
Thank you for telling me how to handle the soil mixture and depth of pea gravel - the lower end of the slope should work fine for that. (There is a 3 inch incline just from the soil underneath the rocks).
I have no idea what type of sedum it is except it appears to be similar to the golden variety of sedum. Next time I go to the nursery where I bought it from I will ask what the name as the plants had no tag name on them.
Rose