It has been just about a month since I decided to transition from organic potting mix (dirt) to mineral based or inorganic's, commonly referred to as "Bonsai soil"(no dirt). Of course, there's a learning curve to work through..it is not as simple as buying a bag of commercial potting mix at the garden center.
In addition to researching the basics & sourcing materials such as lava rock, pumice, calcined clay(fired), decomposed granite, charcoal, one has to start thinking about feeding the trees & other plants that we expect to adapt to a whole new environment. A completely inorganic mix carries no nutrition at all, meaning that we must supply 100% of what the plants need to grow & thrive.
More research into types of plant food, fertilization schema, organic vs manufactured, liquid vs dry & I have only figured out that I will stay with Liquid Seaweed as a "base" component + fertilizers intended for specific types of plants; i.e. a tomato fertilizer for tomatoes; a low-pH fertilizer for acid-feeders like azalea's, maples, etc.; a general purpose fertilizer for decidous trees.
Even though I've only repotted about 1/2 of the collection, I'm beginning to see the differences the new potting mix brings about:
1.) Some of the trees exhibited various degrees of transplant shock, but only 1 casualty, so far (Red Karo) & I'm not sure if the repot was a cause or whether it just contributed to a pre-existing problem, but most of the trees look better, healthier & happier..many of those are showing new growth.
2.) Daily watering time & effort have been cut significantly; also water use has been reduced. I have also adapted a different method for water & feed application..am now using pressurized sprayer & wand, which allows me to put the food & water exactly where it needs to go with less loss to run-off.
3.) Although the initial cost of the components of Bonsai soil are more expensive than commercial potting soil, I am beginning to see the advantages of the ability to re-use inorganic soil, instead of discarding it. I don't know how many bags of commercial potting soil I have gone through over the last 3 years, but now, with the addition of a stainless steel sieve, I can recover the inorganics, like pumice, granite, charcoal, rinse & re-use that material, as it does not degrade over time.
I will continue to report on the conversion to "no dirt" as time goes on.