Raised bed question - building on rock?
I just moved from an area that I used raised beds on because of poor soil, to an area that has NO soil. I am not kidding - the previous owners of the property trucked in about 20 tons of topsoil to get grass growing in the front yard. It took us 2 days to get a small swingset set up in the back because all our set stakes kept hitting rock! The landscape is composed of many large, flat rocks....some over 5' wide. There is some dirt visible, but you can't go down too far without hitting rock again. We have plenty of natural grasses and weeds in the area, so SOMETHING grows.
There is only one logical area on the property for a raised bed - an area that is relatively flat, gets enough sun and is out of the range of our septic sprinklers. I can easily get about 6-8 decent sized beds in there, which is great. I think I can get a good garden growing if I can make each bed 12-18" deep, since of course, this area is all rock. The only problem is, ALL of the beds I've seen constructed this deep require some sort of staking to the ground, and that simply isn't going to happen. I would end up with either skewed beds or odd shapes in order to avoid the rocks, and having done that in the past, I don't want to go there again.
What I need is some sort of bed that maintains its support from the outside of the bed to keep it stable and not shift - like a frame of sorts, but one that isn't anchored. I want to avoid railroad ties and treated lumber. I've done searches on this site and online, but have yet to find something that isn't anchored.
Any tips? Hubby would be pretty ticked off if I took over his front yard grass for my beds. :)