Hi I am just getting into the bonsai hobby. I have bought a Parson's Juniper, a San Jose Juniper, and a Birds Nest Spruce from the local nursery that I will be turning into my first bonsai s. I have a question about soils for these plants. I was going to put them all in conventional clay pots and potting soil at first for a few months and prune and stake, maybe wire them in that environment first (hoping this would be more forgiving of mistakes), then move them to bonsai pots in the late summer/early fall. I live in the mid atlantic region of the US.
I have
1) Hartz's PH5 Cat litter, seems to be mostly clay particles with no strange additives.
2) Red Lava Rock, which I probably need to crush into smaller chunks
3) Coarse Sand, which is closer to sharp pebbles
4) well composted potting soil from the garden, most of our plants seem to like it a lot
Would any of these comprise a decent mix and in what proportion would you guys suggest? Do I need anything else?