by Jerry Meislik
So many of my friends have and are using a diatomite type material as a soil mix that I have tried to find this material and use it for bonsai soil. One of the few products that I can find was at NAPA automotive- and it is a diatomite particle. I tried using it after screening out the fines over a window screen. A second container of pumic was used as a control. Both pots were moistened and a Ficus burtt-davyi cutting was placed in each container. Both containers were kept out of direct sun and sealed in plastic baggies for about 3-4 weeks. Soil was checked and moistened as needed.
The cutting in the diatomite eventually lost all its leaves and failed to root while the pumice container's cutting rooted - with a root even coming out of the container - and new shoots growing from the cutting. A clear failure for the diatomite.
Conclusions are not firm or even scientific as only one cutting was used:
1. The NAPA diatomite has much smaller particles of 2-3mm and likely stayed wetter than the pumice
2. Burtt-davyi is one species that seems most likely to be unhappy and have root rot in soils that are too moist
3. More trials need to be done to determine the proper mix or type of soils and the best particle size