HELP! Clay Soil in concrete block raised bed on concrete slab
Newbie here with ZERO gardening experience. Please excuse me if this is in the wrong forum, has been asked/answered before, or is a stupid question!
I need soil help!!
So I'm renting an apartment with a back yard that is a concrete slab surrounded by a concrete block wall. There are existing planters made of concrete block along one corner which are filled with dirt. The planters are approximately 16 inches high and 2 feet wide. One side is 66 inches long and other is 86 inches.
There appear to be major drainage problems with the soil that is currently in there. Originally, I had intended on putting down rocks on the bottom to improve drainage, which I read somewhere. But after starting to dig, the top layer seemed to be a decent soil but after removing it the bottom half appears to be clay. It's reddish, sticks together, cracks form on top when dry and water pools when wet. It's also of unknown contamination so I don't want to grow any edibles in the soil.
My question is what to do about the soil. Do I dig it all out? Do I mix it with something? Do I leave it as is? What about added rocks to the bottom? (I just read on this site adding rocks to the bottom of a container is bad-- Do I treat the beds as one large container?) I'm only going to be here for two years and do not want to spend a lot of money on soil that I'm going to leave. I also don't want to waste my time trying to grow in impossible conditions.
I'm currently growing herbs in large pots filled with organic potting soil. My boyfriend wants to half bury the pots in the beds and grow non-edibles in the existing soil around the pots. We're really not picky about what we want to plant other than the herbs. Are there plants that would survive/thrive in the beds as is?
Any advice is greatly appreciated, as I am a newbie! Thanks!!