Earlier this year when I first started becoming interested in plants, not just bonsai, I opted to use regular potting soil with some extra perlite thrown in for better drainage and avoiding soil compaction. My houseplants did fine in this mix. Eventually I grew tired of that and started using cactus/succulent potting mix from Schultz (or maybe Miracle Grow). The succulents fared alright, but I feel like they would have grown a better root structure had I used a mostly inorganic mix.
As I have started to get more serious about bonsai lately, I decided that I should really work on making my own soil mix. Of course by soil mix I really mean a mostly inorganic substrate that allows adequate drainage, holds moisture, and allows the roots to get the oxygen they need. Earlier in the week I purchased a bag of NAPA Floor Dri #8822 and a bag of poultry grit from Tractor Supply Company. The Floor Dri is actually diatomaceous earth, which the the bag says was calcined by firing it at a high temperature. The poultry grit is actually just crushed granite granules and happen to be almost perfectly sized before it’s even been screened. The Floor Dri has at least twice as many fines as the poultry grit, but they look like they could useful for cuttings and mame.
My mix is 2 parts diatomaceous earth and 1 part crushed granite. The crushed granite has a nice purple color when wet. I wetted the left side so you could see the difference between wet and dry.
Since I had all of this new mix to use, I went ahead and repotted all of my succulents. It will be interesting to see how they handle being in a completely inorganic mix. I’m not sure where to find a good supply of pine bark fines to mix in, but I think this mix will be fine for my other trees for now. Outside next summer may be something different, however.
Oh and I also made a hardwood ficus cutting and stuck it down in a small terra cotta pot filled with my new mix.
I think I may cut off one of those “branches” on the top, but I haven’t decided yet. I’ll keep it in a humid environment for a while and hope that it takes root. I did dab on a little rooting hormone, but ficus shouldn’t really need it. My last cuttings didn’t take root because I didn’t really create a suitable environment for them. I can’t wait to see this one start pushing out new growth.