I fully expect to be assassinated or visited by those infamous BMB’s (Bonsai Men in Black) for revealing this information, for indeed it is one on bonsai’s best-kept secrets. This knowledge has been withheld from the general public for many years and the veil of secrecy dates back to when plants were first being containerized in the Hanging Gardens of Babylon, when the Chinese and Japanese were first creating bonsai, when Europeans first discovered bonsai in Asia, and right up to this day where even the experienced masters weave a web of mystique around soils and bonsai. However, I feel it is high time that the simple truth was spoken, so here it goes. . .
I have spent a long time studying soil mixes and components, reading every single thing there is on soils; container gardening and the horticultural needs of bonsai and all paths lead me to the following conclusion.
Bonsai can be grown in almost anything that is not poisonous!
You could grow bonsai in glass shards, garden dirt, marbles, metal shavings, gravel, wood chips, moss, crumpled up newspapers, crushed concrete, discarded keys, chopped up automobile tires, yes anything! Chipped plastic, cut up milk cartons, broken beer bottles, crushed tiles, thumbtacks, pocket change, gold bits, old teeth, deer antlers, discarded electronic components, yard waste, small children toys, anything!
The secret is not in the components that make up a soil mix. The only thing you need is something that will retain a little water and also allow drainage. The secret is solely in the attention you give the bonsai in your choice of soil mix.
Go into your bathroom and open up the medicine cabinet, close your eyes and count to 13, now, while keeping your eyes closed, shut the medicine cabinet door. The first thing you see when you open your eyes now will be the secret ingredient.
It’s the care yougive! When your soil isn’t performing it usually means that it is not matched to the level of care you give or it has “worn” out. You change your soil to match this level or you change your care to match the soil…or, of course you replace it because it has “worn” out.
You could fill a bowl with marbles and successfully grow a bonsai in it if you are able to perform the near constant watering and feeding that such a mix would require. Go to your local dentist and take home all the discarded teeth, add some water retentive material like bits of cut up sponge to the mix and you could grow a bonsai in it. Garden dirt, potting soil, crushed toilet seat covers could all be used as well. Blasphemy you say? Not quite, as long as you closely monitor your watering and are prepared to re-pot often, it can be and is done.
So why does everyone swear by their own mix? Simply because the mix they use conforms to their personal schedule of care, nothing more, nothing less. Change the annual rainfall amount; the temperature, the watering or feeding schedule of the individual and the mix will fail for them.
We mix soil to conform to our personal climate conditions as well as our personal care schedule and we tend to use readily available, affordable materials that have been proved to work in a wide variety of climates by simply adding a little more of one and less of another.
The actual ingredients are not important as long as they perform the required functions, which is why even in the same one square mile area, bonsaists will have different soil mixes. This is also why so many debates center around the best ingredients, we fail to realize the simply truth that it’s not the ingredient that matters, it’s the function.
And what is the function of soil components? Retaining water, air and nutrients while anchoring the tree would be the common answer which any materials that are non poisonous could provide. Bonsai also require the formation of fine feeder roots to assure optimal conditions in the confines of a pot and to create good nebari.
In closing lets take a common mix of 1/3 lava rock, 1/3 turface, and 1/3 bark and replace the ingredients with others. Would 1/3 glass shards, 1/3 chopped auto tires, and 1/3 cut up sponge work as well? Would a Lenz worthy mix of 1/3 small plastic toy skeletons, 1/3 crushed concrete, and 1/3 sphagnum moss work as well?
I may well be leaning toward the ridiculous here to prove a point and for that I apologize; yet the point needs to be made. There is no secret ingredient that will make your bonsai thrive, only your care can do that, the soil you choose must fit in with your ability to give the care it requires.
It is not the ingredients that matter; it’s the function of such and the ability of care given to match the soil choice.